A COLORTMETRIC PROCEDURE FOR THE DETERMENATIQN 0F ARSENIC, CHROMEUM, AND COPPER EN WOOD TREATED WITH WATER-BORNE PRESERVATWES Thesis far the Degree of Ph. D. MECHEGAN STATE UNNERSITY Vishwa Nafh Prasad Mathur 1964 mats IIIIIIIIIIIIIIIIIII IIIIIIIIIIII , mm I" 31293 01072 0369 Michigan State University This is to certify that the thesis entitled A Colorimetric Prodecure for the Determination of Arsenic, Chromium and Copper in Wood Treated with Water-borne Preservatives presented by Vishwa Nath Prasad Mathur has been accepted towards fulfillment of the requirements for Ph.D. degree in Wood Technology 5% 4WD Major professor Date NOV . 25 , l 961+ 0-169 ABSTRACT .A COLORIMETRIC PROCEDURE FOR THE DETERMINATION OF ARSENIC, CHROMIUM, AND COPPER IN WOOD TREATED WITH WATER-BORNE PRESERVATIVES by Vishwa Nath Prasad Mathur A colorimetric method is described for the rapid and accurate quantitative determination of arsenic, chromium, and copper in wood treated with water-borne preservatives. ,A wet digestion method, utilizing sulfuric acid and hydrogen peroxide, has been satisfactorily used for destruction of the wood substance and subsequently bringing the elements to be analyzed into water solution. By reacting with sodium molybdate-hydrochloric acid solution, the arsenic present in the preservative solution or the digested wood solution is completely con- verted to 1,2 molybdoarsenic acid. The 1,2 molybdoarsenic acid is extracted from the water solution into Butan-l-ol. Following separation it is possible to make a colorimetric measurement of the alcohol layer at 370 mp. Removal of suspected interfering ions is also described in the procedure. From the study of the determination of arsenic from different species of treated wood and various preser- vative formulations it is found that a precision of more than 95 per cent is achieved. Vishwa Nath Prasad Mathur Chromium is extracted with ethyl acetate and determined colorimetrically at 565 mp. in the form of blue perchromic acid. Only hexavalent chromium is converted to blue perchromic acid by the action of hydrogen peroxide. A procedure for oxidation of the chromium content into hexavalent state is also described. It is found that chromium can be determined by the blue perchromic acid method with an accuracy of more than 95 per cent, irrespec- tive of the species of the treated wood and the preservative formulation tested. Copper is determined by the "cuproine" method which is specific for copper (I). This method is satisfactorily used to determine copper with an accuracy of more than 98 per cent. All the copper content of the solution is brought to copper (I) state by reducing it with hydroxyl ammonium chloride (NHZOH HCl). A copper (Il-cuproine complex is formed which can be extracted with isoamyl alcohol. The colorimetric measurements are then made on this alcohol layer at 546 mp. Copper has been determined with an accuracy of more than 98 per cent from all the species of treated wood and preservative formulations tested. ,A comparative test on the determination of arsenic, chromium, and capper by the volumetric method and the colorimetric method show excellent agreement between the two methods. However, the colorimetric method has addi- tional advantages in that smaller sample sizes can be used and less time is taken for analysis. A COLORIMETRIC PROCEDURE FOR THE DETERMINATION OF ARSENIC, CHROMIUM, AND COPPER IN WOOD TREATED WITH WATER-BORNE PRESERVATIVES by Vishwa Nath Prasad Mathur A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Forest Products 1964 ACKNOWLEDGMENTS The author wishes to express his sincere appreciation and gratitude to Dr. E. A. Behr for his guidance throughout this investigation. The guidance offered by Dr. A. J. Panshin and Dr. 0. Suchsland is also deeply appreciated. Acknowledgments are gratefully extended to Dr. R. L. Guile, Dr. A. Timnick of the Department of Chemistry, and Dr. J. Lubkin of Metallurgy, Mechanics, and Materials Science for their generous assistance. The author takes this opportunity to express his deep appreciation and gratitude to his wife Leela Mathur and his parents, Mr. and Mrs. R. P. Mathur, whose sacri- fices made it possible for him to undertake the Ph.D. program. ii TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . . . LIST OF TABLES. . . . . . . . . . . . . LIST OF ILLUSTRATIONS . . . . . . . . . INTRODUCTION. . . . . . . . . . . . . . Water-borne Preservatives . . . . . The Principle of Colorimetry. . . . Statement of the Problem. . . . . . REVIEW OF LITERATURE. . . . . . . . . . methOdS Of AnaIYSiS . . . . . . . . Recent Developments in Colorimetric Colorimetric Method for Copper. . . Colorimetric Methods for Arsenic. Colorimetric Methods for Chromium Digestion Methods . . . . . . . . EQUIPMENT AND REAGENTS. . . . . . . . . EXPERIMENTAL PROCEDURE AND RESULTS. . . Preparation of Treated Wood Samples Digestion Procedure . . . . . . . . Determination of Copper . . . . . . Separation Techniques . . . . . Determination in Solution . . . Determination of Copper by Cuproin Determination in Treated Wood . Effect of Arsenic and Chromium. Effect of Suspected Interfering Io Effect of Species of Treated Wood Determination of Chromium . . . . . In Solution . . . . . . . . . . In Treated Wood . . . . . . . . Effect of Copper and Arsenic. . Effect of SuSpected Interfering Ions Reagents. ....:1..(D..... Effect of Species of Treated Wood . iii M ..........d-..... 0.........0..... Page ii Determination of Arsenic. . . . . . In SOIUtiOn . . . . . . . . . . In Treated WOOd . . . . 0 . . . Effect of Copper and Ch omium . . . Effect of Suspected Interfering Ions Effect of Species of Treated Wood . Comparative Study of Volumetric and Colorimetric Methods. . . . . . . . . DISCUSSION OF THE RESULTS . . . . . . . . . . Copper Analysis . . . . . . . . . . . . . Chromium Analysis . . . . . . . . . . . . Arsenic Analysis. . . . . . . . . . . . . Comparative Study of Volumetric and Colorimetric Analyses . . . . . . . . CONCLUSIONS 0 O O O O O O O O O O O O O O O O FUTURE STUDIES 0 O O O O O O O O O O O O O 0 O BIBLIOGRAPHY. O O O O O O O O O O O O O O O 0 APPENDIX I O O O O O O O O O O O O O O O O O 0 iv 0 0 O O O O Page 60 61 69 69 71 72 8O 80 81 83 85 86 88 89 93 LIST OF TABLES Table Page 1. Active ingredients in various proprietary preservatives . . . . . . . . . . . . . . . 2 2. List given by Johnson (24) on the various derivates of ferroin group with their absorptivity values for Fe (II) complex and cu (1) complex. O O O O O O O O O O O 0 11 3. Comparative results from perchromic acid method and diphenyl carbazide method for determining chromium from ethyl acetate extraction, as reported by A. Glasner and M.Steinberg(16)............. 22 4. Comparison of visible ultraviolet non- recording spectrophotometers. . . . . . . . 26 5. Determination of c0pper in the effluent solution after extraction of copper by ion exchange resin (Amberlite 120). . . . . . . 37 6. Calibration data for determining copper in standard solution by cuproine method. . . . 41 7. Calibration data for determining copper in treated wood by cuproine method . . . . . . 43 8. Effect of arsenic and chromium on determina- tion of copper by cuproine method . . . . . 46 9. Effect of suspected interfering ions on the determination of copper (100 pg.) by the colorimetric method . . . . . . . . . . . . 48 10. Effect of species of treated wood on the determination of copper by the colorimetric methOd. O O O O O O O O O O O O O O O O O O 48 ll. Calibration data for determining chromium in SOIUtiOn. O O O O O O O O O O O O O O O O O 52 12. Calibration data for determining chromium in treatedWOOd................ 55 V Table 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Effect of arsenic and copper concentrations on determination of chromium. . . . . . . . Effect of suspected interfering ions on the determination of chromium (500 pg.) by the COlorimetriC methOd . . . . 0 . 0 . . 0 . . Effect of species of treated wood on the determination of chromium by the COlorimetriC methOd . . . . . . . . . . . . Calibration data for determining arsenic in SOlUtiOn. O O O O O O O O O O O O O O O O 0 Standard calibration for arsenic in treated WOOd..0................. Effect of copper and chromium ions on the determination of arsenic. . . . . . . . . . Effect of suspected interfering ions on the determination of arsenic. . . . . . . . . . Effect of species of treated wood on the determination of arsenic by colorimetric methOd................... Scheme for analysis of water-borne preservative treated wood . . . . . . . . . Comparative analysis to determine water-borne preservatives by volumetric and colorimetric methods. . . . . . . . . . . . vi Page 57 59 59 64 67 70 7O 71 74 79 LIST OF ILLUSTRATIONS Figure Page 1. Spectronic 20 spectrophotometer. . . . . . . 27 2. Treated wood sample for colorimetric and volumetric analyses. . . . . . . . . . . . 32 3. Absorbance vs. copper content in solution, calibration graph. . . . . . . . . . . . . 42 4. Absorbance vs. copper content in treated wood, calibration graph. . . . . . . . . . 44 5. Absorbance vs. chromium content per ml. of ethyl acetate in the determination of chromium in solution . . . . . . . . . . . 53 6. Absorbance vs. chromium content per ml. of ethyl acetate in the determination of chromium from treated wood . . . . . . . . 56 7. Absorbance vs. arsenic content in solution, calibration graph. . . . . . . . . . . . . 65 8. Absorbance vs. arsenic content in treated wood, calibration graph. . . . . . . . . . 68 vii INTRODUCTION Wood preservatives are chemical substances which, when applied to or impregnated into wood, make it resis- tant to attack by fungi, insects, or marine borers. Preservatives may be classified into two main groups: the water-borne preservatives and the oily, or oil-borne, preservatives. This thesis is devoted to water—borne preservatives. Water-borne Preservatives The chief constituents of water-borne preservatives are the compounds of arsenic, chromium, copper, fluoride, and zinc. Almost all of the proprietary preservatives available on the market today consist of one or more than one compounds of these elements, as shown in Table l. Toxicity of these preservatives towards various agencies of wood deterioration are different and have been under study since the evolution of the wood preserving industry. For effective preservation of wood and wood products, it is essential that the treated product contain more than the lethal dosages of these chemical constituents. Both the treating solution and the treated wood may be analyzed for determining the retention of the constituents involved. In practice, only the strength of the treating solution, 1 .coaumaseuom w>dum>uomoum us» ca ucmmmum mucoapoumcH + .coaymaseuom m>wum>uommua was» ad Hammond uoc muamdomumcH I .munmmo ucuumm .m .6 .mmm. .m4m02m0 .maqdeZmo Am mdmeImeumo .m meme I + I + + .Hocmcm uneconu< meounu Hoaam .m .maq4m zfipm>uommwm mucoacomeH m>aau< IIII III .mobaum>uommum hhmumaumoua m90dum> ca mucodcoumcd m>auuua>duauomnd mom >ua>aumuomn< MHSEHOM HMUHEmEU IIII .onQEou AHV nu cam onmEou AHHV mm Mom modam> hua>auau0mnm Hausa suds msoum cwouumm mo moum>wuoc mSOAum> on» so Avwv cOmccon hp co>Hm umHAII.N wanes 12 Other copper specific reagents in this series are neocuproine and bathocuproine. An excellent bibliography on cuproine, neocuproine, and bathocuproine is available in the pamphlet by Diehl and Smith (11). Sodium diethyldi- thiocarbamate, dithiozone, and potassium ethyl xanthate reagents have also been used for the colorimetric deter- mination of c0pper. The limitations of these methods with their advantages and disadvantages are discussed by Snell and Snell (36). However, these reagents were not selected for the present work as they have been shown to lack sensitivity, selectivity, and stability. Edge (13) has found that carboxylic acid cation exchange resins can be used with success in determining copper in chromated wood preservative solutions. He has used the resin column to separate copper from other metallic ions of the solution and later recovered the copper with hydrochloric acid. For the purpose of deter- mination of copper he used the volumetric method. Ion exchange resins have also been used in industry for separation of copper from other ions. From the various methods described the cuproine method was selected for this work. The major considera- tions for selecting this method were: 1) Specificity.--2,2' Biquinoline is specific for copper. Breckenridge, Lewis, and Quick (8), Hoste (15) (19-22), and later Guest (17) found that none of the following cations gave color 2) 3) 13 reaction with the reagent: NH4+, Li, Na, K, Rb, Cs, Be, Mg, Ca, Ba, Al, La, Ce (III), Ce (IV), Nd, Sm, Ti (IV), Zr, Th, V (V), Nb, Ta, Cr (II), Cr (III), Mo (VI), w (VI),U0 **, Mn, Fe (II), 2 Fe (III), Ru, Co (II), Rh, Ir, Ni, Pd, Pt, Ag, An, Au, Zn, Cd, Hg (I), Hg (II), Ga, In, Tl, Ge, Sn (IV), Pb, As (III), AS (V), Sb (III), Sb (V), Pn, Se (IV), Se (VI), Te (IV), Te (VI). The titanous ion gives a pale green color which cannot be confused with the purple color of cuprous- biquinolene compound. Some ions, of course, inter- fere because of their own color, nickel for example; none of these is extracted into isoamyl alcohol. Among the anions, the following anions do not affect the cuprous biquinoline cation: acetate, borate, bromide, chloride, chlorate, perchlorate, tartrate, nitrate, sulfate, and phosphate. Cyanide, thiocyanate, iodide, and oxalate anions do interfere. According to Smith (11) 0.008 pg.of copper in 1 ml. of water gives a detectable color. The sensitivity of the detection of copper with biquinoline may be improved by extracting the colored copper with an immiscible solvent. The purple cuprous-biquinoline compound is soluble in isoamyl alcohol, benzyl alcohol, hexyl alcohol, benzene, carbon tetrachloride, chloroform, ethyl l4 acetate and amyl acetate. The partition coefficient is greatest in isoamyl alcohol and this solvent is used in this work. 4) The extraction with isoamyl alcohol of cuprous biquinoline gives an excellent method of separation of copper from the digestion mixture obtained either from the usual perchloric acid method or the new peroxide method. The color is very stable for many days. However, fading has been reported and has been ascribed to oxidation of the cuprous com- pound either by air or by an oxidizing impurity in isoamyl alcohol used for extraction. No trouble is experienced if an excess of reducing agent is present. Colorimetric Methods for Arsenic Arsenic compounds have been used as wood preservatives for a long time. At the present time arse- nic is determined volumetrically in research laboratories as well as in treating plant laboratories. Until recent years, small quantities of arsenic were determined nearly exclusively by the Gutzeit method (33), but now its position is seriously threatened by the rival molybdenum blue method and the 1,2 molybdoarsenic method. An excellent review of the determination of arsenic has been reported by the Analytical Methods Committee of the Society for Analytical Chemistry, England, and reported in the Analyst (41). Arsenic used to be separated as 15 arsenious chloride from hydrochloric acid solution or by volatization of arsenic as arsine, which in turn is decomposed into elemental arsenic by passage through a silica tube heated to 800°C. The chief source of error in the procedure is likely to be the incomplete absorption of arsine. Trivalent arsenic can be extracted, from acid solutions, as xanthate, by carbon tetrachloride. Other metal xanthates, which are also extracted, can be removed from carbon tetrachloride by washing with concentrated hydrochloric acid containing stannous chloride. W. J. Wilson (44) determined arsenic in treated wood by modifying a volumetric method proposed by Schulek and Villecz (34). In this method a one gram sample of treated wood is decomposed with concentrated nitric acid and sulfuric acid, reduced with hydrazine sulfate solution, and the excess of the reagent decomposed by fuming. The solution is titrated with 0.01N ceric sulfate solution in the presence of osmium tetraoxide using ferrous O-phenanthroline perchlorate as a catalyst. Sandell (33), Snell and Snell (36), and other standard treatises on colorimetric analysis give the details and variations of the molybdenum blue method. Of the several variants of the molybdenum blue method (23) (30) (37) (38) and (45), the procedure recommended by the Analytical Methods Committee of the Society of Analytical Chemistry, England, for the determination of small amounts of arsenic in organic matter follows most closely the 16 method proposed by Wyatt (45). ,In this method the organic matter is destroyed by wet digestion and the arsenic, after extraction with diethylammonium diethyldithiocarba- mate solution, is converted to the arsenmolybdate complex, which is then reduced by means of hydrazine sulfate to a molybdenum blue compound and determined absorptiometri- cally at a wave length of 840 mp. Since working at 840 mp. requires adjustment of the instrument (replacing the photo— tube with a red sensitive tube and putting a red filter in the path of incident radiation), this method was not considered further. However, the arsenomolybdate complex mentioned earlier has been thoroughly investigated by Waldelin and Mellon (43). They investigated the character of the absorption spectrum of the colorless 1,2 molybdoarsenic acid solution in the near ultra violet region. They applied the familiar process of liquid-liquid extraction of the heteropoly acids from water into certain organic solvents. ‘It was found that 1,2 molybdoarsenic acid can be extracted from the aqueous phase into butan-l-ol. Following extraction it is possible to make absorption measurements at 370 mp.where the molar absorptivity for arsenic is 5100. Waldelin and Mellon have reported the effect of 48 diverse ions along with methods for pre- venting interference from soluble silica, iron, and small amounts of orthophosphates. l7 Tanaka and Hiiro have proposed several methods for determination of arsenic with quincetin (39), rutin (40), and morin (18) reagents. However, these methods require separation of arsenic from the organic matter by the usual arsine method followed by extraction with com- plex forming agents (rutin, morin, etc.) and later eva— poration of the solvent. The arsenic complex is then brought into alcohol solution and the absorption read at known wave length (440 mp.). As these methods require heating, evaporation, and waiting periods for the color to develop, they were not found useful for this work. Colorimetric Methods for Chromium Chromium salts in water-borne preservatives basically are used because of their property of fixing the other components (e.g., copper and arsenic) in the treated wood (25) (29). The fixation of chromates and dichromates consists of their reduction by the constituents of the wood to chromium ion, which forms a stable bond with the con- stituents of the wood. Somewhat similar but probably rather more complex changes take place when a copper- chrome—arsenic solution is used (42). Potassium or sodium dichromates, chromic acid, and sodium chromate have been in use in many of the patented water-borne preservatives. In the usual volumetric analysis chromium is determined as hexavalent chromium iodometrically or by a back titration method with ferrous ammonium sulfate and standard potassium dichromate solution (2). 18 Various colorimetric methods have been prOposed for quantitative determination of chromium in the iron and steel, chromium plating, and leather tanning industries. According to Sandell (33) the most useful method for the separation of chromium involves oxidation in the basic media, whereby chromate is formed and remains in solution, while a great many metals such as iron, titanium, manga- nese, nickel and cobalt, etc. are precipitated. The oxi- dation can be effected in hot solution with sodium peroxide/hydrogen peroxide and sodium hydroxide. In acid media oxidation can be achieved with persulfate in the presence of silver as a catalyst. Other common agents for oxidation of chromium to the hexavalent state are bismuthate, permanganate, bromine, and silver oxide. It is always necessary to destroy the excess of the alkaline oxidant. Peroxide will reduce chromium (VI) in acid solution. Boiling in alkaline solution is the procedure employed for the destruction of peroxide, which is the usual alkaline oxidant employed. This reaction is very slow and the last traces of peroxide are very difficult to remove. If ferric ammonium sulfate is added as catalyst, or ferric or nickel oxides are present in the solution, ten minutes boiling is sufficient. For the highest accuracy, or in the case of traces of chromium, a secondary oxidation is employed with permanganate solution. The outstanding colorimetric method for the determination of chromium is that which depends on the l9 intense red-violet color developed on the addition of a solution of s—diphenyl carbazide to an acidified solution of a chromate or dichromate. Numerous research papers have been published on the nature of the reaction, prepa- ration of the reagent, stability and sensitivity of the color reaction. A very good summary of the exhaustive work on s-diphenyl carbazide chromium complex is provided by Kolthoff, Elving, and Sandell (26). Mann and White (28) extracted the chromium (IV) with trioctyl phosphine oxide in benzene, then measured the color by addition of alco- holic diphenyl carbazide directly to the benzene extract. There are too many interferences with the diphenyl carbazide method. It is reported (33) that the chromium reading will be about ten per cent low if copper is present in amounts 500 times the chromium concentration. Iron, mercury, and vanadium have also been found to affect the determination of chromium by this method. A colorimetric determination of chromium has also been proposed (33) in which the absorption of its alkaline solution is read at a wave length of 374 mp. The general procedure is to convert chromium to the hexavalent state, adjust the pH to 8.5 to 9.5, and take an aliquot of S to 100 parts per million of chromium. The absorbance is measured at 365 to 370 mp.and is compared with the stan- dard, which should be adjusted to the same pH and inert salt concentration as the unknown. Since preparation of a standard solution of the same inert salt content (copper, 20 arsenic, etc.) is laborious, this method is not very effective. An extremely stable complex of chromium (III) is formed with ethylenediaminetetraacetic acid (6), but its formation is very slow at room temperature although it proceeds rapidly on heating. Several investigators have reported on the possible use of EDTA complex with chro- mium (III) and the effect of interfering ions, pH of the solution, etc. Boef, DeJong, Krijin, and Poppe (6) (7) critically investigated the spectrophotometric determi- nation of chromium (III)-EDTA complex. They suggested that separation by EDTA or TTA produces better results than oxidation to chromate. However, their procedure is laborious and time consuming. Majumdar and De (27) report on the use of TTA (2-thenoyltrifluoroacetone) for the direct determination of chromium (III) in the organic phase. Their method gives a simultaneous extraction and colorimetric method for milligram amounts of chromium (III) on the basis of the formation of an orange chelate with TTA, which is extractable with an organic solvent such as benzene. The colored system is reported to be stable for a week. The colored solutions produced by this method conform to Beers Law at 430 mp.over the concentration range of 8 to 200 pg. of chromium (III) per ml. The wave length 430 mp,is very critical; plus or minus 5 mp.gives a very large difference in the absorbance reading. Due to the limitation of the 21 colorimetric instruments used in this study, this method did not give satisfactory results. Brookshier and Freund (9) report determination of chromium as perchromic acid, which can be extracted with ethyl acetate and determined photometrically as the blue perchromic acid at a pH of 1.7 i .2 at 20‘C. The perchro- mic acid could be formed by reducing dichromate ions with hydrogen peroxide in acid media. The presence of organic liquids and lower temperature stabilizes the perchromic acid formed. Large amounts of iron, manganese, vanadium, molybdenum, and tungsten do not interfere. Beers Law is observed. Glasner and Steinberg (16) proposed the sepa- ration of chromium from vanadium by extraction of perchro- mic acid with ethyl acetate, to be determined subsequently, by the possibility of using ethyl acetate extractions for determination of chromium without going through the diphenyl carbazide method. They confirmed the finding of Brookshier and Freund, i.e., that the aqueous solution at equilibrium should have a pH of 1.7 i .2 and that the ethyl acetate extracts are fairly stable up to 20°C. They also compared their perchromic acid results with those of the diphenyl carbazide method and found that the perchromic acid method gave better results (see Table 3). Glasner and Steinberg also reported that the absorbances are a linear function of the concentration of the dichromate, up to and somewhat above the absorbance of one, and indepen- dent of the mineral acid used. Foster (14) of the U. S. 22 Table 3.--Comparative results from perchromic acid method and diphenyl carbazide method for determining chromium from ethyl acetate extraction, as reported by A. Glasner and M. Steinberg (16). Initial amount Chromium by perchromic Chromium by diphenyl of chromium acid method carbazide method Mg. Mg. % Mg. % 0.05326 0.05334 100.2 0.05154 96.8 0.1065 0.1057 99.2 0.1025 96.3 0.1598 0.1611 100.8 0.1552 97.1 0.2130 0.2128 99.9 0.2058 96.6 0.2663 0.2647 99.4 0.2554 95.9 23 Geological survey reported that the perchromic acid method can be applied in mineral analysis, provided chromium is present in the amounts of 0.5 to 5 mg. A modified blue perchromic acid method is used in this work because of the simplicity of the procedure and accuracy of the results. Digestion Methods All the colorimetric methods discussed so far can only be applied to the respective ions in solution. In the case of treated wood, the first problem is to bring the ions to be determined (e.g., arsenic, chromium, and copper) into solution by destroying the organic matter. This process is known as digestion or ashing. Dry ashing used to be the standard method for digestion in the wood preserving industry but in recent years the wet digestion (3) procedure has been utilized. The main disadvantages of the dry ashing method, according to Sandell (33), are that copper may be lost, owing to the reaction with other constituents of the ash. It is also probable that copper may react with the vessel used for ignition to form sparingly soluble copper compounds. Chromium could be volatized as chromylchloride if chloride ions are present in the wood. The wet digestion of organic matter employing hot concentrated perchloric acid is discussed by Smith (35). The American Wood Preservers' Association has also incorporated the wet digestion method in their manual (2). 24 However, the most exhaustive study on the destruction of the organic matter (both dry and wet ashing) has been done by the Analytical Method Committee of the Society of Analytical Chemistry, England (42). They have considered various combinations of the acid (nitric, sulfuric, etc.) and oxidants (perchloric acid, hydrogen peroxide, etc.) according to the elements that are required to be analyzed after the destruction of the organic matter. Because of the study reported above, it was not thought wise to repeat the work to find a suitable method of ashing the treated wood. A critical review of the method prOposed indicated that the wet digestion using sulfuric acid and/or nitric acid with perchloric acid or hydrogen peroxide would give complete destruction of the organic matter as well as retain all the ions which are to be determined by colorimetric methods. Since the handling of perchloric acid is hazardous and serious accidents are possible, the hydrogen peroxide method has been adopted. The details of this method will be given later on pages 31, 33 and 34. EQUIPMENT AND RBAGENTS 1. Colorimeter.--The selection of the colorimeter for commercial testing plant use depends on its available wave length range, sensitivity, and the initial and main- tenance cost. Though recording type instruments are available in the market, they were not used for these experiments for economic reasons. Table 4 gives a compa- rison of the features available in different reading types of colorimeters. Since a B and L Spectronic 20 colori— meter was available and its features qualify it for the present investigation, all the experiments were carried out on it. Many other instruments which give the same or better performance can also be used. Bausch and Lomb's "Spectronic 20," shown in Figure l, is a versatile instrument and is available at low cost. It is useful for both spectrophotometric and colorimetric measurements. The specifications and other details of this instrument are described in Table 4. B and L colorimetric specimen tubes of 3/4 inch diameter were employed in these experiments. 2. pH Meter.--Where not otherwise mentioned, a Beckman Model N pH meter was used throughout these experi- ments to determine the pH of the solution. 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On the right hand side of the colorimeter are shown the B and L colorimetric tubes in their rack. In the foreground (from right to left) the first three watch glasses show the form of one gram samples of treated wood which can be used for colorimetric analysis. The fourth watch glass shows the treated and untreated wafer and the microsyringe used for treatment. The treating solution is shown in the volumetric flask. The two white capped bottles contain 84 grams of ground sample required for volumetric analysis. 28 places, pHydration paper AB-pH 1-11 and pH 1.2-2.4 manufactured by the Micro Essential Laboratories, Inc., Brooklyn 10, New York, was also used in the procedures for the determination of arsenic, copper, and chromium respectively, in order to obtain a general idea of the pH of the solution. For precise measurement (in the chromium analysis) the pH meter was used. 3. Reagents.--All the reagents used in these experiments pass A.C.S. specifications. The colorimetric reagents for the determination of copper were purchased from G. F. Frederick Smith Company of Columbus, Ohio. A complete list of reagents used for the volumetric method of analysis is given in Appendix I. The reagents for colorimetric analysis are described with the procedure for analysis. 4. Cleaning solution.--A "Wash acid" consisting of 50 ml. of nitric acid (sp. gr. 1.42) and 150 ml. of. hydrochloric acid (sp. gr. 1.19) in 200 ml. of water is recommended by Saltzman (32) for cleaning glassware in which chromium in acidic media has been kept for a long duration. Saltzman's "Wash acid" was used for cleaning glassware. For general cleaning purposes, a detergent solution (TideR) was used in these experiments. After cleaning with the detergent solution or wash acid, the glassware was thoroughly washed with tap water, followed by twice washing the glassware with double distilled water. 29 5. Redistilled water.--The copper content of distilled water obtained from the Chemistry Department was determined to be 0.2 pg/ml. This warranted another distillation in all glass vessels. The copper content of this redistilled water was found to be less than one hundredth microgram per milliliter. EXPERIMENTAL PROCEDURE AND RESULTS Preparation of Treated Wood Samples The usual preservative impregnation techniques could not be applied successfully to impregnate microgram to milligram quantities of preservative ingredients to achieve an accuracy of 95 per cent or more. The procedure given below was followed for preparing treated wood samples: The wood to be treated was cut into a wafer (1/8" thick and 3/4" wide). A piece weighing one gram (1.05 gram) was cut from it. This weighed piece was laid flat on two glass rods which supported the edges of the sample. A known volume of the solution was introduced on the flat surface drop by drop through a microsyringe. Care was taken that all the solution introduced was absorbed by the wood sample only. Only 0.6 ml. of the solution could safely be placed on the surface at a time. If more solution had to be introduced, this was done after a time interval long enough for all previous treatments to be absorbed, so that the sample had dried sufficiently to be able to absorb more. Generally, with a drying time of 12 hours or overnight, the solution could be added in steps of 0.6 ml. or less. The sample was 30 one 31 dried for at least 48 hours at room temperature after the desired volume of the solution was introduced in it. The dried sample of known ingredient content could either be placed on a glass plate and cut into thin slices (see Figure 2) or made into a powder by placing it in a micro Wiley mill (see Figure 2).' The treated wood sample could now be digested by the procedure given below. Digestion Procedure Reagents.-- l) Sulfuric acid, concentrated 96 per cent (arsenic content less than 6 x 10-7 per cent). 2) Hydrogen peroxide 30 per cent. Acid/oxidant: Two volumes of 30 per cent hydrogen peroxide plus one volume of sulfuric acid. Procedure.--The following procedure was used for gram treated wood samples in sliced form: The accurately weighed sample was placed in a 150 ml. beaker. Two or three boiling chips were added to prevent bumping. Fifteen milliliters of the acid/oxidant solution were gradually added. The beaker was then kept on a hot plate at medium heat and allowed to boil for ten minutes. If any charring was noticed or the color of the resulting solution ‘Figure 2 also shows the comparative sizes of samples required for colorimetric and volumetric analysis. 32 Figure 2.-—Shows the comparative size of sample required for colorimetric and volumetric analysis. Each watch glass contains one gram of treated wood sample. The left hand bottom watch glass shows sliced wood, the top one shows ground wood sample, and the remaining watch glass shows sliced increment boring. The two bottles, shown on the right, contain 84 grams of ground wood sample required for volumetric method of analysis. 33 turned black, the beaker was removed from the hot plate and cooled. A few drops of hydrogen peroxide were added and the contents again boiled. This step was repeated until the final color of the solution was light orange to light yellow. The contents were cooled to room temperature. In the case of treated wood of high chloride content (CZc, CuCZc treated wood), the above procedure was modified. Before addition of acid-oxidant solution, 10 ml. of nitric acid (1:10) were added and allowed to soak into the wood. The contents of the beaker were heated at low heat so as to start a vigorous reaction in which the sample seemed to be charred. The contents were cooled and acid/oxidant solution added. The procedure given in the previous paragraph was followed thereafter. For the ground sample, the beaker was replaced with an appropriate Kjeldahl flask (for one gram sample 100 ml. flask was used and for ten gram sample 500 ml. flask was used). The Kjeldahl flasks were heated at low heat from gas burners instead of a hot plate. The procedure of digestion was the same as that followed for sliced wood with the only modifi- cation that for a five gram sample, 50 m1. of the acid/oxidant solution was used. The digested solution was transferred into a 50 ml. volumetric flask. The beaker/Kjeldahl flask, in 'I’ II). in"! ll‘ '1‘ 34 which digestion was carried on, was washed twice with 5 ml. 1:1 ammonium hydroxide or 10 per cent sodium hydroxide solution and the alkaline solution added to the volumetric flask. This flask was then cooled to room temperature and redistilled water was added to bring the level of the contents up to the mark. Determination of Copper Copper has been used in water-borne preservatives as copper sulfate (CuSO4'5H20), copper hydroxide (Cu(OH)2), and cupric chloride (CuC12’2H20). The intention has been to analyze both preservative solutions and treated wood by a rapid method and to determine a content range of 20 to 200 pg.of copper per gram of treated wood or per milliliter of the treating solution with a precision of more than 95 per cent. Separation Techniques It has been mentioned that 2,2' Biquinoline (cuproine) forms a purple cuprous—cuproine compound which can be extracted by various organic liquids, e.g., isoamyl alcohol, benzene, carbon tetrachloride, chloroform, or ethyl acetate. Hoste, Eeckhout, and Gillis (22) have recommended isoamyl alcohol, since it has the highest partition coefficient. Guest (17) showed that a shaking time of one minute using isoamyl alcohol is sufficient to establish equilibrium if the pH of the aqueous solution is between 4.4 and 7.5. The extraction method fits in with [luli illll 35 the procedure for quantitative determination of copper described in the next section. Determination in Solution Ion exchange resins have been used for the separation of copper from aqueous solutions containing chromium and arsenic. A screening experiment was performed to ascertain the suitability of this method. Amberlite 120 cation exchange resin was used. The copper cation is held by the resin while the anions containing chromium (Cr207_-) and arsenic (AsO4---) pass through the resin column. The effluent solution can then be analyzed for chromium and/or arsenic. Preparation of ion exchange column.--A 25 ml. buret was used for the column. A paste of Amberlite 120 resin in water was prepared and poured into the buret so as to make a column. The resin column was supported on a glass wool plug. Ten millimeters of 6N sulfuric acid were then poured into the buret and allowed to soak through the resin at a flow rate of 0.25 ml. per minute. When the liquid level reached the top of the resin bed, another 10 m1. of 6N sulfuric acid were poured in and repeated the process of soaking. The resin bed was thus made ready for the separation of copper from the preservative solution con— taining 6N sulfuric acid. This normality of the acid was chosen because it was the same as that present in the digestion solution. 36 Procedure.--Five ml. of the preservative solution (2 per cent Erdalith), adjusted to 6N sulfuric acid con- centration, were then poured gradually into the column and the flow rate adjusted to 0.25 ml. per minute. When the level of the preservative solution reached the top of the resin bed, 5 ml. of 6N sulfuric acid were added, followed by two 5 m1. portions of redistilled water. The effluent solution was collected in a 150 ml. beaker. The copper content of this effluent solution was determined by the cuproine method (described on pages 38-40). The copper from the resin bed was removed by passing 20 ml. of 3N hydrochloric acid through the resin bed at a flow rate of 0.25 ml. per minute. Results.—-Table 5 gives the amount of the copper ion detected in the effluent preservative solution. It is found that 98 to 99 per cent of the copper was extracted by the resin. The ion exchange resin method is effective in separating the copper of the preservative solution from chromium and arsenic ions of the solution. However, it has been found to be a very time consuming method, because one analysis takes at least 1-1/2 hours for 5 ml. of the sample. Further, in the determination of copper, the extracted copper from the resin has to be brought back into solution and then determined by the cuproine method. It was due to the time factor that this method was not adopted. 37 Table 5.--Determination of copper in the effluent solution after extraction of copper by ion exchange resin (Amberlite 120). Copper present in Copper found in Erdalith solution effluent solution Recovery % P9. P9. 1680 34 98 3360 30 99.1 5040 36 99.3 6720 42 99.3 8400 50 99.4 Notes: The 2 per cent Erdalith solution was prepared by dissolving 2.2431 grams of potassium dichromate in 50 ml. distilled water and 10 ml. of concentrated sulfuric acid. To this were added 1.32 grams of copper sulfate (CuSO 'SHZO) and 0.44 grams of sodium arsenate. The volumg of the solution was then adjusted to 100 ml. Copper was determined by the cuproine method described on pages 38-40. 38 Determination of Copper by Cuproine Method Reagents.-- Cuproine solution: A 0.1 per cent solution of cuproine was prepared in isoamyl alcohol. Isoamyl alcohol: Redistilled isoamyl alcohol as supplied. Hydroxylammonium chloride: A 10 per cent solution was prepared in water by dissolving ten grams of hydroxylammonium chloride in 100 ml. of redistilled water. Copper content of this solution was checked by adding a few ml. of cuproine solution and then 10 ml. of isoamyl alcohol. The solution was shaken and separated into layers. It was found that the copper content of isoamyl alcohol showed no purple color and the absorbance at 546 mpowas zero as compared to pure isoamyl alcohol. Standard copper solution: A standard solution containing 20 pg.copper per ml. was supplied by the G. Frederick Smith Company of Ohio. Another standard solution containing 100 pg;copper per milliliter was prepared by dissolving 0.3926 gram of copper sulfate (CuSO4'5H2O) in 1 liter of redistilled water. Procedure.--The following procedure is used for extracting and determining copper content of 20 to 200 pg. from an aqueous solution of pH 5-6: [l I III. I I .Ill'llllll III ll .1!!! Illllll .1 l. l 1"“ .l‘ l‘ l (Ill-(1| £5].Ihllu III! .I ujllllfll lull! .l. Ii (11 I 39 An aliquot sample of the preservative solution was pipetted into a 125 ml. separatory funnel. Five ml. of 10 per cent hydroxylammonium chloride were added. The pH of this solution in the separatory funnel was adjusted to 5 to 6 with dilute ammonium hydroxide solution or 1:10 sulfuric acid, using a pH paper. Two ml. of the cuproine solution were added followed by the addition of 10 ml. of isoamyl alcohol. The separatory funnel was shaken for one minute and the contents allowed to separate into layers. The lower aqueous layer was poured into another separatory funnel and the alcohol layer poured into a 25 m1. volumetric flask. The aqueous layer was extracted again with 10 ml. of isoamyl alcohol and, after one minute of shaking, the layers were separated. The isoamyl alcohol layer was added to the volumetric flask and the volume was brought to 25 ml. with iso- amyl alcohol. If desired, the aqueous layer could be saved for the determination of chromium or arsenic or both. The extraction of copper was thus complete. The isoamyl alcohol collected was then poured into a 50 m1. beaker, and one gram of sodium sulfate was added to absorb any traces of water. The absorbance of this solution was then determined against isoamyl alcohol at 546 mp. It was observed that it was better to find the transmittance first, as its scale is divided equally throughout the full range from zero 40 to 100 per cent. From a standard conversion chart the transmittance could be converted to the absorbance reading. Preparation of standard calibration curve.—- Following the procedure laid down in the previous section, the absorbance was measured for known amounts of c0pper by taking samples from the standard solutions. The absorbance data have been presented in Table 6 and Figure 3. Determination in Treated Wood Samples of wood containing known amounts of copper were prepared with the standard copper solution (100 pg/ml.) according to the procedure described on pages 30 and 31. For bringing the pH of the digested solution to 5-6 both sodium hydroxide and ammonium hydroxide could be used. However, when sodium hydroxide was used, the pH was never allowed to go above 7, due to the possibility of precipi- tating the copper hydroxide. Copper hydroxide forms a soluble complexion in ammonium hydroxide; hence a 1:1 solution of ammonium hydroxide was used. A standard calibration curve was prepared for treated wood, similar to the one described above for solutions. Treated wood samples containing 20 to 200 pg. copper were prepared and the absorbance data were collected, as reported in Table 7 and Figure 4. Sugar pine wood was used in this experiment. A control sample (one gram of untreated wood) was also used, and it (I!!! 41 Table 6.--Ca1ibration data for determining copper in standard solution by cuproine method. Volume tested COpper present Standard solution Absorbance ml 0 Pg: G. Frederick 10 20 .114 Smith Company standard solution 20 40 .232 containing 2 pg.copper/ml. 40 80 .460 60 120 .690 80 160 .920 100 200 1.150 Standard solution 0.2 20 .112 prepared in lab. containing 0.4 40 .232 100 pg.c0pper/ml. 0.6 60 .348 0.8 80 .455 1.0 100 .580 1.2 120 .680 1.4 140 .810 1.6 160 .900 1.8 180 1.020 2.0 200 1.155 42 $1100-51 .namum coaumundamu .soauaaom ca usmucou ummaou .m> musmnuOnn «UGMQHOmQ4II.d musmwm 3 ONVBHOSB V 45 furnished the zero reading of absorbance for the data of all treated wood samples. The standard calibration curve was prepared as shown in Figure 4. The slopes of both graphs are the same, and the calibration curve is a straight line. Effect of Arsenic and Chromium Standard solutions for chromium (100 Pg/ml.) and arsenic (100 Pg/ml.) were prepared and known amounts of these were added to 1 ml. of the standard copper solution (100 pg/ml.). The procedure laid down in this section was followed and copper content was determined. From the absorbance data collected, the amount of copper was determined from Figure 3. Table 8 presents the collected data and the per cent of error in the determination of copper. For studying the effect of chromium and arsenic ions on the determination of copper in treated wood, the samples of treated wood containing known amounts of copper, chromium, or arsenic, or both, were prepared by the procedure given on pages 30 and 31. These samples were digested and the cuproine method followed to determine copper with the aid of Figure 3. Table 8 presents the collected data and the per cent of error in the determination of copper. 46 Table 8.--Effect of arsenic and chromium on determination of copper by cuproine method. COpper found in Error found in Copper Arsenic Chromium present present present solution wood solution wood 99» 119: pg. p9. pg. % % 100 0 0 100 101.3 . . 1.3 100 10 0 100.6 101.4 0.6 . 1.4 100 30 0 100.2 101.8 0.2 1.8 100 60 0 101.0 98.6 1.0 -l.4 100 100 0 101.8 102.2 0.8 2.2 100 0 50 99.9 101.3 -0.1 1.3 100 O 100 100.8 101.6 0.8 1.6 100 0 200 100.6 99.8 0.6 -0.2 100 O 400 100.2 101.6 0.2 1.6 100 0 600 100.2 102.1 0.2 2.1 100 -30 170 100.8 101.4 0.8 1.4 47 Effect of Suspected Interfering Ions Contact with wood treating equipment sometimes results in pickup of ions such as iron and zinc by the preservative solution. Phosphates and silicate ions could be contributed by the wood or might enter treating solutions from other sources. These may affect the analysis of copper by the cuproine method. It has already been reported that the cuproine method is specific for copper (I) and iron, zinc, phosphate, or silicates do not interfere. However, to make sure that the method proposed on pages 38-40 can be successfully applied to the analysis of commercial treating solutions and treated wood, the effect of these ions was also tested. Table 9 gives the effect of these interfering ions. Effect of Species of Treated Wood All the work on the treated wood was done on one species only, namely, sugar pine. A study was undertaken at this stage to determine if there is any effect of the species of treated wood on the determination of copper by the colorimetric method described on pages 38-40. Southern yellow pine, Douglas fir, and red oak were the other three species of wood that were tested. Only the colorimetric method of analysis for copper was used, and the samples were prepared according to the procedure given on pages 30 and 31 by adding 1 ml. of 2 per cent Erdalith solution to a one gram wood wafer of each species. Table 10 presents the data collected. 48 Table 9.--Effect of suspected interfering ions on the determination of copper (100 pg) by the colorimetric method. ._-_: __—:___:—_: Suspected interfering Added as Amount added Error ion pg. % Fe FeCl3 400 1.80 SiO3 Na25i03 400 0.30 P04 NH4H2PO4 400 0.40 Zn ZnCl2 400 0.50 Table 10.-—Effect of species of treated wood on the -determination of copper by the colorimetric method. Specie of wood Copper present Copper found Error pg. f9. % Sugar pine (Pinus lambertiana) 1680 1684 0.23 Southern yellow pine (Pinus sp.) 1680 1692 0.71 Douglas fir (Pseudotsuga menziesii) 1680 1686 0.36 Oak (Quercus rubra) 1680 1698 1.07 49 Determination of Chromium Sodium chromate, sodium dichromate, and potassium dichromate are the most common ingredients of proprietary preservatives used in the wood preserving industry. The colorimetric method selected is based on the principle of formation of blue perchromic acid, which can be extracted in ethyl acetate followed by measurement of the absorbance of the extract at 565 mp. Only hexavalent chromium forms the blue perchromic acid. Therefore, the first step in the analysis is to convert all chromium present in the solution to the hexa- valent state. In dichromate and chromate ions, Chromium is present in the hexavalent state. If chromium is present in the trivalent state, it first has to be oxidized to the hexavalent state. Reagents.-- l) Ethyl acetate-—anhydrous—-Baker's analyzed. 2) Hydrogen peroxide 30 per cent. 3) Dilute hydrogen peroxide solution: 11.4 ml. of 30 per cent H 0 reagent was diluted to 100 m1. 2 2 with redistilled water. 0.5 ml. of dilute H202 solution in 25 ml. aqueous solution would give 0.02M H202. 4) Sulfuric acid--l:l: Gradually added 10 ml. of redistilled water to 10 ml. of sulfuric acid. 5) pH 1.7 buffer solution: 107 ml. of 0.2N hydrochloric acid was added to 250 m1. 0.2N 50 potassium chloride solution and then diluted to 1000 ml. with redistilled water. Standard chromium (VI) solution: Weighed 0.2844 gram of potassium dichromate. Redistilled water (850 ml.) was adjusted to pH 1.5 with 1:1 H2504 and poured into a liter volumetric flask. Weighed potassium dichromate was then added and volume adjusted to 1 liter. The chromium (VI) content of this solution was 100 pg/ml. In Solution An aliquot sample of the standard solution was pipetted into a 150 ml. beaker. The pH of the solution was adjusted to 1.7 I .2 with either 1:1 sulfuric acid or 1:1 ammonium hydroxide. The volume of the solution was brought to 25 ml. with the buffer solution. The sample was then transferred to a 125 ml. separatory funnel provided with a glass stopper. Thirty ml. of ethyl acetate (anhydrous) were pipetted into the beaker in which the pH was adjusted. Ethyl acetate was then transferred to the separatory funnel containing the sample solution. The separatory funnel was cooled to 0-10‘C by keeping it in a refrigerator for fifteen minutes. Then 0.5 ml. of dilute hydrogen peroxide solution was added to the cooled sample-solvent mixture. The separa- tory funnel was gently shaken for thirty seconds and then the layers were separated. The lower layer (aqueous) was transferred to another 125 m1. separatory funnel and the 51 ethyl acetate layer collected in a 50 m1. graduate. To the aqueous layer another 10 ml. of ethyl acetate were added and the separatory funnel shaken for thirty seconds. The layers were separateda-the aqueous layer transferred to the first separatory funnel and the ethyl acetate layer to a 50 ml. graduate. One more extraction with 5 ml. of ethyl acetate was performed. The aqueous layer could be saved for determination of some other ions if required (e.g., arsenic). The ethyl acetate—perchromic acid solution in the graduate was brought up to the 50 ml. mark with ethyl acetate. The extraction of chromium (VI) was thus completed. An aliquot of the blue perchromic acid-ethyl acetate solution was transferred to a 3/4" colorimeter test tube and the absorbance measured at 565 mp.against a blank. Aliquot samples of standard chromium (VI) solution were analyzed by the procedure just described. Table 11 presents the collected data on the absorbance reading for known chromium (VI) and the same data have been plotted in Figure 5. In Treated Wood Treated wood samples containing 100 pg.to 2 mg. were prepared by the procedure described on pages 30 and 31. The procedure laid down for digesting treated wood (pages 31, 33, and 34) was followed. The pH of the digested 52 Table ll.--Ca1ibration data for determining chromium in solution. ‘I' _—: ‘1; ' Chromium present Chromium present per ml. in solution of ethyl acetate Absorbance pg. Pg/ml. reading 50 1 .02 10° 2 .042 150 3 .064 200 4 .083 25° 5 .102 500 10 .205 75° 15 .305 1000 20 .408 1250 25 .512 1500 30 .615 1750 35 .718 2000 40 .820 2500 50 1.030 53 .coHuSHOm CM EDHEOLLO wo coHpmcfiEnmump one CH mumumom H>Luw mo .HE 501 ucmucoo EDHEOLLO .m> mocmnpomb< ua.m opswfim I. _ _ _ 5 _ 5 _1 _ _ 1 _ _ 1 _ _ 1 _ _ _ _ 1 _ H O 9 0.0 7 6 5 4 3 2 l I O O O O O O O 0 O muz Br + 3A5 + 31520). In both cases the excess of oxidizing agent can be destroyed by boiling. However, it should be remembered that other ions which are present in their reduced form would also be oxidized. For example, cuprous ion, which would react as follows: (6Cu+ + BrO3- + 6H+-"> 6Cu++ + Br" + 3H20). The presence of copper (Cu++) does not affect the determination of arsenic. Chromium ions can be extracted from solution by the ethyl acetate extraction technique described on pages 35 and 36. Phosphates and silicates present in the solution also form heteropoly acids similar to 1,2 molybdoarsenic acid. The 1,2 molybdophosphoric acid could be selectively extracted with chloroform, in which the partition coefficient for 1,2 molybdoarsenic acid is negligible. The 1,2 molybdosilicic acid forms slowly; hence the effect of silicate ions could be avoided if the absorbance measurements could be taken within six minutes from the time sodium molybdate solution has been added. In Solution Reagents.-- 1) Sodium molybdate-hydrochloric acid solution: Fifteen grams of sodium molybdate dehydrate were dissolved in 200 ml. redistilled water. Eighty-four 62 m1. of concentrated hydrochloric acid were added and diluted to 500 ml. The resulting molybdate- hydrochloric acid solution was stored in a plastic bottle. 2) Butan-l-ol B.P 117.0 to 118.5°C. 3) Standard arsenic solution: 0.384 grams of As O 2 5’ of purity 99.5 per cent, was placed in 150 m1. redistilled water and heated to 60°C. When disso- lution was complete, the solution was cooled to 25°C and diluted to 250 m1. This solution con- tained 1.0 mg. arsenic/ml. and was stored in a plastic bottle. 4) Chloroform-butan-l—ol solution: 300 ml. of chloroform and 100 m1. of butan-l-ol. 5) Hydrochloric acid 1:1. 6) Sodium hydroxide 10 per cent, stored in a plastic bottle. An aliquot sample from the standard arsenic solution (containing 0-1 mg. arsenic) was pipetted into a 125 ml. beaker and the volume of the sample brought to 20 ml. with redistilled water. The pH of this solution was then adjusted between 5 to 9. The contents were transferred to a separatory funnel. Ten m1. of sodium molybdate solution were then poured into the beaker used for adjusting pH, and next transferred to a separatory funnel. Twenty ml. of chloroform-n butyl alcohol solution were added and the 63 funnel shaken for thirty seconds. The layers were then allowed to separate and the bottom chloroform layer was discarded. The process of extraction with 20 ml. of chloroform-n butyl alcohol solution was repeated twice. The phosphate ions, if present, would be extracted with the chloroform layer. To the chloroform washed aqueous solution, 20 ml. of n butyl alcohol were added. The separatory funnel was shaken for thirty seconds and then allowed to separate into layers. The aqueous layer was transferred to another separatory funnel and the butanol layer was collected in a 50 m1. graduate. The extraction procedure was repeated with 20 m1. n butyl alcohol and the butyl alcohol layer added to the 50 m1. graduate. The alcohol layer was then brought up to the 50 m1. mark with the addition of n butyl alcohol. The absorbance was read immediately, if the presence of silicate ions were suspected, at 370 mp. against a blank in 3/4" colorimetric test tubes. The absorbance A was measured by following the procedure described for the determination of arsenic in solution, using known amounts of arsenic and taking aliquot samples from the standard solution. The absorbance data have been presented in Table 16 and plotted in Figure 7. 64 Table 16.--Ca1ibration data for determining arsenic in solution. Arsenic present Pg’ Absorbance 5 .011 15 .028 25 .048 35 .066 so ' .090 65 .118 75 .140 90 .164 100 .180 150 .280 200 .400 400 .690 800 1.300 1000 1.600 000_ .50050 coaumunflamu .COflDDHOm CH pcmucou uwsmmum .m> mononuOmQ musowm 00m 00m CON 220010 01 000 com 00¢ 00m OON OO_ O _ a _ a _ _ . _ _ _ BDN V0 HOSBV 66 In Treated Wood Treated wood samples were prepared by following the procedure given on pages 30 and 31. Treated wood samples were digested according to the procedure described on pages 31, 33 and 34. To assure that the arsenic present in the digested wood solution was in pentavalent form, the pH of the solution was raised to 9 with 1:1 ammonium hydroxide or 1N sodium hydroxide. Then 1 ml. of 30 per cent hydrogen peroxide was added and the excess of hydrogen peroxide destroyed by boiling for ten minutes. (Nickel oxide can be used as a catalyst.) The solution was cooled and the volume made up to 50 ml. When chromium was not present the oxidation could be carried out in acid media by adding 5 ml. of 1N potassium bromate solution, removing the excess of bromate/bromine ion by boiling for ten minutes. A 20 ml. aliquot of the solution was taken for the determination of arsenic, as described on pages 61-63. The absorbance measurements were recorded against that of a blank, which was made by following the same procedure on one gram of untreated wood. A standard calibration curve relating the absorbance and arsenic content in wood was prepared by following the above procedure on wood containing known amounts of arsenic from 0-1 mg. The absorbance data collected has been recorded in Table 17 and the same has also been plotted in Figure 8. 67 Table l7.—-Standard calibration for arsenic in treated wood. Arsenic present Arsenic in aliquot Absorbance pg. P9- 50 10 .019 100 20 .038 150 30 .054 200 40 .072 400 80 .150 600 120 .226 800 160 .290 1000 100 .182 68 .zmmum coavmunflamu .pooz 9000050 CH uc0pcou uwc0mum .m> 0ucmnuomn4 04' .56 ”Q 100 300 500 .55 txg' (,5 04 Table 19.--Effect of suspected interfering ions on the determination of arsenic. Suspected interfering Added as Amount added Error ion pg. % Fe FeCl3 400 10.5 SiO3 Na23i03 400 2.8 PO4 NH4H2PO4 400 4.9 Zn ZnCl 400 —0.6 2 71 Effect of Species of Treated Wood The species described on page 47 were studied for their effect on the determination of arsenic. The treated wood samples were prepared according to the procedure described on pages 30 and 31, by adding 1 ml. of standard arsenic solution (100 pg./ml. to one gram sample of each wood specie studied. Table 20 presents the collected data. Table 20.--Effect of species of treated wood on the determination of arsenic by colorimetric method. Specie of wood Arsenic present Arsenic found Error pg- 149. % Sugar pine (Pinus lambertiana) 100 100 . . Southern yellow pine (Pinus sp.) 100 101.5 1.5 Douglas fir (Pseudotsuga menziesii) 100 98.0 -2.5 Oak (Quercus rubra) 100 103.5 3.5 72 Comparative Study of Volumetric and Colorimetric Methods All the proprietary preservatives given in Table 1 were prepared according to the A.W.P.A specifications for per cent ingredients in each preservative (2). The treated wood samples were prepared by the following procedure: Five grams of sugar pine (Pinus lambertiana) were weighed to the nearest 0.01 gram. The weighed wafers were placed in a beaker and this beaker was kept in a dessicator, which was attached to a water vacuum pump. Full vacuum was pulled for ten minutes. The preservative solution was then introduced into the beaker, through the separatory funnel, and the vacuum pump was turned off. Sufficient solution was used so as to cover the wafers completely. The wafers were left submerged in the treating solution overnight to obtain maximum absorption. The waters were then removed from the solution, wiped lightly to remove surface preservative, and immediately weighed to the nearest 0.01 gram. The gain in the wafer's weight was recorded as the grams of treating solution absorbed and the retention was calibrated as: Retention(gm./gm. wood) = (gm. of treating solution)(strength of treating solution) 100 x grams of sample 73 The treated wafers were dried at room temperature for two days followed by oven drying at 50°C for 24 hours. The dried wafers were converted into powder small enough (to pass 10 mesh) in a micro Wiley mill. The powder was weighed to the nearest .01 gram and digested in a 500 m1. Kjeldahl flask. The wet digestion with sulfuric acid and hydrogen peroxide was carried out according to the procedure described on pages 31, 33 and 34. The digested solution was made up to 100 ml. in a volumetric flask. Aliquot samples of the digested solution were analyzed for arsenic, chromium, and copper according to the procedure described in the A.W.P.A. Manual (2). Table 22 presents the collected volumetric data for each item. A scheme followed for the colorimetric analysis of various water-borne preservative treated wood is shown in Table 21. The digested solution formed the starting point for the analysis. An aliquot sample of the digested solution (1 ml. to 10 ml. containing 20 pg. to 200 pg. of copper) was taken for the determination of copper. The procedure followed has already been described on pages 38-40, which can be summarized as: added 10 m1. of 10 per cent NH OH'HCl and 2 adjusted pH of the resulting sample solution to 5-6 in a 125 ml. separatory funnel. Two ml. of 0.1 per cent cuproine reagent solution were added and followed by 10 m1. 74 .00 0000 50 005550000 005005 0500 0550050005>505 m.5l0500 0550055 .vm 050 5m 00000 50 005550000 005008 0500 0580550500 0355 >5 53550550 .m0 050 00 00000 50 005550000 005005 05505030 >5 500000 m N 5 0550055 0550055 0550055 53550550 AK UHCGmH< .HUI ESHEOHSU \ A 0550055 50! 53550550 53550550 0550055 50! 53550550 AK IK AL .HUI 50! 83550550 53550550 500000 53550550 500000 500000 500000 500000 505000 m 0055 505050 00050055 080550 50350 505000 5 00MB 505050 00050055 050550 50350 A5N00 00050055 055M 000080550 50N0300 00550550 055N 000050550 0005500000 50500 00550550 055N 000050550 55000 00050055 500000 000080550 A5N0300 00050055 055N 005050550 0005500000 500<0 00050050 500000 05u< 55050 00050055 500000 5000550855 0030550 050000 0000550 00055 0>500>500050 “500000 050 .53550550 .0550050 055850000 00 0003 003 050500 055305500 055 .0003 003 50500050x0 83580550 50050 055550505 50503500 0300300 050 m0550050 00 5050055850000 500 00 050800 0030550 0505 m.53550550 055850000 00 0030550 5050050 050 5500000 055850000 .0530x58 00550500 50005055 050 0500 05530530 5053 050500 000050 .0003 0000050 0>500>500050 05505I50003 00 050M5050 500 08050mll.5m 0550B 75 of isoamyl alcohol into the funnel. A shaking time of one minute brought the copper (1)-cuproine complex thus formed into the alcohol layer. The layers were separated and the alcohol layer was then transferred into a 25 ml. volumetric flask while the aqueous layer was transferred into another separatory funnel. Another extraction was made with 10 ml. isoamyl alcohol and the alcohol layer added to the volu— metric flask. The contents of the flask were made up to the mark with fresh isoamyl alcohol. Any traces of water were removed from the alcohol collected by transferring it into a 50 m1. beaker containing one gram of sodium sulfate. An aliquot sample was transferred into a colorimetric tube and absorbance measured at 546 mp. against the blank. The absorbance reading was converted into the copper content of the sample (with the help of calibration graph, Figure 4). From the collected data (09. copper/gram of sample), it was easy to determine the active ingredient present as gram per gram of the wood or as pounds per cubic foot by using the following conversion factors and equation: Active Ingredient (gm./gm. wood) MUltlplylng Factor Cuso4 2.511 x 10‘6 CuSO4'5H20 3.928 x 10"6 CuC12°2H20 2.682 x 10'6 Ingredient in lb./cu. ft. = 62.43 x ingredient(gm./ gm. wood) x specific gravity. ‘l'lfll' {ff'lllllll 76 Chromium was determined by taking another aliquot sample from the digested solution. This procedure, given in detail on pages 50 and 51, calls for oxidation of the sample in alkaline media with peroxide. The excess of peroxide was destroyed by boiling for ten minutes in the presence of nickel oxide or ferric ammonium sulfate. The pH was then adjusted to 1.7 i .2 with sulfuric acid. Addition of buffer solution brought the volume to 25 ml. which was transferred to a 125 ml. separatory funnel. Anhydrous ethyl acetate (30 ml.) was then added and the contents brought to a temperature of O-lO‘C. To the cold contents of the funnel, 0.5 m1. of the dilute hydrogen content of the peroxide was added to make 0.02M H O 2 2 aqueous phase. A shaking time of thirty seconds was enough to form blue perchromic acid and extract it into the acetate layer. The acetate layer was collected in a 50 m1. volumetric flask and the aqueous layer transferred to another separatory funnel. The extraction procedure was repeated with 10 ml. and 5 ml. ethyl acetate, and the acetate layer added to the first acetate collection. The aqueous solution could be saved for the arsenic analysis. An aliquot sample was transferred into a colorimetric tube and absorbance measured at 565 mp. against a blank. The absorbance reading for chromium was converted into the chromium content of the sample with the help of cali- bration graph, Figure 6. From the collected data on chro- mium content (in Pg. chromium per gram of sample), it was 77 easy to determine the active ingredient present as gram per gram of wood or as pounds per cubic foot of treated wood by using the following conversion factors and equation: Active Ingredient (gm./gm. wood) MUltlplylng Factor -6 NaZCrO4 3.115 x 10 o -6 NaZCrZO4 2H20 5.731 x 10 -6 KZCrZO7 5.657 x 10 Ingredient in lb./cu. ft. = 62.43 x ingredient(gm./ gm. wood) x specific gravity of wood. Arsenic was determined by the procedure on pages 62 and 63. In the case of ammoniacal copper arsenite an aliquot sample from the digested solution could be taken for arsenic analysis, and in other preservative formulation the aqueous layer collected after chromium extraction formed the starting point for arsenic analysis. An aliquot sample (20 ml.) was adjusted to a pH of 5-9 and 10 ml. of a sodium molybdate solution were added to it in a separatory funnel. Interference from phosphate ions was eliminated by thrice extracting with 20 m1. of a chloroform-normal butyl alcohol (3:1) mixture. The 1:2 molybdoarsenic acid was then extracted with 20 ml. of n butyl alcohol. A shaking time of thirty seconds was used and extraction with butan-l-ol was repeated with another 20 ml. of n butyl alcohol. The alcohol layers were I'll-‘llill '1’ Ill“l|l 78 collected in a 50 m1. volumetric flask and made up to the mark with the addition of n butyl alcohol. An aliquot sample was transferred into the colorimetric tube and absorbance measured at 370 mp. against a blank. The absorbance reading for arsenic was converted into the arsenic content of the sample with the help of Figure 8. From the collected data of arsenic content (in Pg. As/gm. of sample) it was easy to calculate the active ingredient present as grams/gram of wood or as pounds/cubic foot of wood by using the following conversion factors and equation: Active Ingredient (gm./gm. wood) MUltlplylng Factor A5203 1.30 x 10'"6 A5205 1.534 x 10"6 NaZHAsO4 2.482 x 10"6 Na2HAsO4'7H20 4.165 x 10-6 Ingredient in lb./cu. ft. = 62.43 x ingredient(gm./ gm. wood) x specific gravity. The comparative analysis data collected has been presented in Table 22. From other sources‘ a few samples were received with their own analytical data. These samples were analyzed by the procedure laid above for the colorimetric determination of copper, chromium, and arsenic in preservative treated wood. The results are presented in Table 22. ‘A government agency and a private firm. 79 8...- 3.8. 8.. o... 8.. 2.8. o~:~.mo~£ R... 038. $2 3.. 29 838. N $309 3.. :38. ..3n 3. man 9:8. 9 :3. .833 8.0. :3 .32. «a £83 8.3- 8.8. NS 38. 33 28. o~zmwo~m< i3 88. ...m 3.“. «SM 58” N 9.5 g .o.. 38. 4.... 8o. 0?. 38 o :3 . 83 3.0. :3 .30... .... 0.8.3 N» 00.53 “c9599.... ... 8.8. 3.. 2.. 0.... . .8. .5229: ”A. 33.8. 23 .8. 08 3.8. :05}... 83 8.80. 5: m8. 3 88. ..83 .... 0......3 83 38. m... 3.. 8.. 38. ..o... 55.9.. c. “conga “55.5309, “pagans... 32. 3.3%. cu u_:...E...o.0u 35. 31.0.; o 295...; 15.00.55. groan-Lac. alumina... 3050... 07:05:20”. 0:0 u.._uo_=:.0> >0 mo>Za>LomoLn 0527.30) 056.32. 3 31.2.0 03.93950 .2 a... ... I'llll Elillllli IlliIII‘I' I 'lil DISCUSSION OF THE RESULTS Copper Analysis The cation exchange resin method for extraction of copper ions from the treating solution was found to give sufficient accuracy (100 i 5 per cent). However, this method suffers from the great drawback that it has been found to be very time consuming. The cuproine method has been found to be very sensitive and satis— factory as well as less time consuming. One hundred per cent recovery of copper was achieved and the precision of determination was plus or minus 2 per cent. The calibration graphs (Figures 3 and 4), relating absorbance and copper content in solution, as well as in treated wood,turned out to be straight lines for the copper concentrations studied. Further, the slopes of these straight lines were also found to be equal which proves that the digestion and extraction procedure gave one hundred per cent recovery of copper content. The procedure described for the extraction of copper levels ranging from 20 to 200 Pg. can also be extended to higher limits. Where more than 20 pg. of copper were present, extractions were continued until there was no visible purple color in the isoamyl alcohol layer. The total 80 I‘ll] i ['1 lll'lllll lllllll' lll‘l,"|vlal|l[ll|x‘| '1' !l|ll 81 alcohol layer was brought to the nearest multiple of 25 ml. and a sample of this was then taken for absorbance measurement at 546 mu. The results obtained in studying the effect of chromium, arsenic, zinc, iron, phosphate, and silicate (see Tables 8 and 9) show that these ions do not interfere in the determination of copper. This confirms the pre- vious finding as reported in the literature survey on pages 12 and 13. In studying the effect of the species of treated wood in the determination of copper, the results show (see Table 10) that c0pper can be determined accurately regard- less of the species of treated wood. This is simply because the digestion procedure brings the entire copper content of the sample into solution form and because an untreated control specimen of the sample species was used for adjusting the zero scale of absorbance. Chromium Analysis The data collected on the standard calibration curves for chromium content in solution and in treated wood showed that the Beer's Law is obeyed from O to 2.5 mg. of chromium (VI) content. Figures 5 and 6 showed the chromium content of the ethyl acetate extract and not the chromium content of the solution or of the treated wood. In these tests 50 ml. of ethyl acetate were used for extraction in samples having 50 Pg. to 2.5 mg. of chromium llillllllllll‘lll" ‘l'rllllllll. 82 content. However, if the sample was smaller than 10 ml. and pH paper was used for adjusting the pH to 1.7 i .2, then a total of 25 m1. of ethyl acetate could be used for extraction of blue perchromic acid. Inasmuch as Figures 5 and 6 present the concentration of chromium per ml. of ethyl acetate, it was found easier to calculate the total chromium content of the sample by multiplying the chromium content in ethyl acetate by the ml. of ethyl acetate used for the extraction of chromium. Furthermore, it was found that the slopes of straight lines of the calibration graphs in Figures 5 and 6 were practically the same. Thus, it could be concluded that all the chromium present in the sample was brought into aqueous solution by the digestion procedure and that all dissolved chromium was extracted from this solution into the ethyl acetate. Table 12 shows that arsenic has no effect on the determination of chromium while copper affects the deter- mination of chromium to a level of 100 plus or minus 5 per cent or less. Thus, in a sample containing copper, chro- mium, and arsenic, one could take an aliquot sample and proceed directly to the determination of chromium without removing the copper, while still achieving an accuracy of i 5 per cent. It was also found that if copper is extracted by the cuproine method and the remaining solution used for chromium analysis, the chromium present is not in the hexavalent state. This can be explained by the fact that the reducing agent used in the cuproine 83 method also reduces chromium into the trivalent state. Hence, to proceed for the determination of chromium, an oxidation to Chromium (VI) was found essential. This was done by the action of peroxide in alkaline media and the procedure is described on pages 51 and 54. The suspected interfering ions had no effect on the determination of chromium by the blue perchromic acid method (see Table 14). Table 15 presents the data on effect of species of treated wood, which is also found to be negligible. The explanation of this behavior is the same as that advanced for the effect of species in cepper analysis (page 79). Arsenic Analysis The calibration curve (Figure 7) for arsenic content in solution shows that a linear relationship exists between the measured absorbance and the arsenic content, from zero to 350 pg. The slopes of the straight line between 0-350 Pg. and 350-1000 Pg. are different, which shows a negative deviation from the Beers-Lambert Law. For treated wood an aliquot sample was taken to give arsenic content between zero and 200 Pg. The slopes of the calibration curves for the determination of arsenic in solution (Figure 7) and treated wood (Figure 8) are found to be equal for all practical purposes. Thus, it can be concluded that both digestion and extraction procedures gave excellent recovery of arsenic. iii‘lll‘fl‘ll 84 The presence of chromium was found to be detrimental to the determination of arsenic by the 1,2 molybdoarsenic acid method. Hence, if chromium ions are suspected, then it was found to be essential that they be extracted before proceeding with the determination of arsenic. The presence of copper did not interfere with the determination of arsenic. It was found that iron, phosphate, and silicate would interfere with the determination of arsenic if their interference was not nullified. Traces of iron present (as tested up to 400 Pg.) do not interfere, however, so that if excess of iron was present, it would be desirable to remove it by precipitation as iron hydroxide in alka- line media. To be more precise, any of the specific colorimetric reagents such as cupferron can be used. Since it was reported that up to 1 mg. of iron can be permitted without interfering with the absorbance measure- ments, cupferron was not used. Phosphate and silicate interference was removed by slightly modifying the procedure. When the modified procedure was used, the error introduced is less than 5 per cent (see Table 19). The species of treated wood did not affect the determination of arsenic as may be seen from Table 20. The reasoning given for copper holds also for arsenic. Il‘l‘ll‘l'l'l‘lll"! .[ . [I (III 85 Comparative Study of Volumetric and Colorimetric Analyses Volumetric analysis requires a large sample if the treatment is made for 0-35 lb./cu. ft. retention from a 2 per cent treating solution. Hence, higher concen- tration solutions were used with greater retention values (see Table 22). Aliquot samples for volumetric and colorimetric analyses were taken from the same digested wood solution for each ingredient to be analyzed (e.g., copper). The comparative data presented in Table 22 for volumetric and colorimetric analyses of the water-borne preservative formulations tested show that equally reliable results are obtained by each method. CONCLUSIONS The colorimetric procedure described for the determination of arsenic, chromium, and copper in solution and treated wood follows the Beers-Lambert Law. The slopes of the standard calibration for the absorbance and concentration of the ion are found to be practically the same for preservative solution as for treated wood. This clearly proves that the digestion method utilizing hydrogen peroxide and sulfuric acid gives complete recovery of the ions to be analyzed. Arsenic, chromium, and copper can be determined to an accuracy of plus or minus 5 per cent by the proce- dure described for the determination of each ion. The rangesof each ion which can be analyzed by the given procedure for the desired accuracy are given below: As (V) 50 Pg. to 1.0 mg. Cr (VI) 50 Pg. to 3.0 mg. Cu 20 to 250 Pg. The upper limit for the determination of these ions is flexible because the preservative solution or the digested solution of treated wood can be diluted to give the desired size of samples. 86 87 The species of treated wood tested in these experiments have been found to have no significant effect on the determination of copper, chromium, and arsenic ions. The expected interfering ions such as iron, zinc, phOSphate, and silicate do not interfere in the colori- metric method of analysis. A comparative analysis of copper, chromium, and arsenic by the volumetric and colorimetric methods revealed that the colorimetric method described gave results as accurately as the volumetric method. All the water-borne preservatives containing arsenic, chromium, and/or copper in any combination can be analyzed both in solution and treated wood to an accuracy of 95 per cent or more by the colorimetric method described in this work. lllllil'nlll'l‘llll [I‘ll-[Illl‘ [(I. I ‘(l FUTURE STUDIES Copper, chromium, and arsenic form the major ingredients of the water-borne preservatives which are presently being used throughout the world. It would be useful to follow up this study with the development of a colorimetric method for analysis of zinc and fluoride ions also. Further, it would be interesting to determine (1) how large (2) how many and (3) from which section of the treated wood the samples be taken for analysis purposes. The present information on this subject is not sufficient specially because the size of the sample can be very small (less than one gram) for X-ray and colorimetric methods of analysis. 88 llillllll!lil[i‘lllll'llllll:'l[[[l'l! 10. BIBLIOGRAPHY American Society for Testing and Material Standards. D 1627-61, D 1326—56, D 1628-61, D 1629-61, D 1033-50, D 1273-56, D 1035-62. In A.S.T.M. Book of Standards, Part 16, Philadelphia, 1958. American Wood Preservers' Association, Standard Manual of Recommended Practice, Washington, D. C., 1964. American Wood Preservers' Association, Committee P-S. Proceedings of American Wood Preservers' Asso— ciation. _§g, 219. 1956. Baechler, R. H. Present Status of Result-Type Specifications for Treated Wood. Rep. Forest Products Laboratory, Madison, Wisconsin. No. 2260. 1962. Belford, D. S. Some Application of Physical Methods in the Study of Preservative Treated Wood. Proceedings 5th World For. Congress. .3, 1557, 1960 (1962). Boef, G. Den, DeJong, W. J., Krijin, G. C., and Poppe, H. Spectrophotometric Determination of Chromium (III) with EDTA. Anal. Chem. Acta. .23, 557, 1960. Boef, G. Den and Poeder, B. C. Spectrophotometric Determination of Cr (III) with Complexans. Anal. Chem. Acta. ‘39, 261, 1964. Breckenridge, J. G., Lewis, R. W. J., and Quick, L. A. 2,2' Biquinoly1--A Reagent for Copper. Can. J. Research, 817, 258, 1939. Brookshier, R. K., and Freund, H. Separation of Chromium from Vanadium by Extraction of Perchromic Acid with Ethyl Acetate. Anal. Chem. 23, 1110, 1951. British Standard Institution Standards. B. S. 3452. Through reference 12. 89 11. 12. l3. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 90 Diehl, H., and Smith, G. F. The Copper Reagents: Cuproine, Neocuproine, Bathocuproine. The G. Frederick Smith Chemical Company, Columbus, Ohio, 1958. Eadie, J., and Wallace, E. M. Some Observation on the Fixation of Copper and Arsenic in Pinus Sylvestris. Journal of Institute of Wood Science. No. 10. Nov.l962. The Institute of Wood Science Limited, London. Edge, R. A. Use of Carboxylic Acid Cation Exchange Resin in the Analysis of COpper in Chromated Wood Preservatives Solutions. Anal. Chem. Acta. 32, 143, 1961. Foster, M. D. Contributions to Geochemistry. U. S. Geological Survey Bulletin. No. 950, 15, 1946. Gillis, J., Hoste, J., and Fernandez-Caldas, E. Determination of Traces of Copper in Plant Materials. Anales edajol. y. fisol. vegetial (Madrid) 2, 585, 1960. Through reference 11. Glasner, A., and Steinburg, M. Photometric Determination of Chromium as Perchromic Acid in Ethyl Acetate Solution. Anal. Chem. 21, 2008, 1955. Guest, R. J. Determination of Copper in Metallurgical Materials: Use of 2,2' Biquinoline. Anal. Chem. ‘25, 1484, 1953. Hiiro, K., Tanaka, T., and Watanaki, S. Spectrophotometric Determination of Arsenic with Morin. Bunski, Kagaku lg (10), 918, 1963. Hoste, J. 2,2' Diquinolyl, A Specific Reagent for Copper. Research (London) 1, 713, 1948. Hoste, J. On a New Copper Specific Group. Anal. Chem. Acta. .4, 23, 1950. , Heiremans, A., and Gillis, J. Colorimetric Determination of Copper with Cuproine. Mikrochemie ver Mikrochim Acta. '36, 349, 1951. , Eeckhout, J., and Gillis, J. Determination of Copper with Cuproine. Anal. Chem. Acta. ‘2, 23, 1953. Jacobs, M. B., and Nagler, J. Colorimetric Microdetermination of Arsenic. Ind. Eng. Chem. Anal. Ed. ‘14, 442, 1942. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 91 Johnson, W. C. Colorimetric Reagents: Some Recent Developments and Their Historical Background. J. Roy Inst. Chem. 81, 39, 1963. Kinberg, W. The Fixation of Chromium Compounds in Wood. Holz als Roh. und Werkstoff. ‘14, 186, 1956. Kolthoff, I. M., Elving, P. J., and Sandell, E. D. Treatise on Analytical Chemistry Part II. .8. Interscience Publishers, New York. Majumdar, S. K., and De, A. K. Extraction of Chromium (III) with 2-Thinoy1trif1uoro acetoen. Anal. Chem. 32 (10), 1337, 1960. Mann, C. K., and White, J. C. Extraction of Chromium with Trioctylphosphine Oscide from Acidic Solutions of Alkali Metal Salts. Anal. Chem. 29, 989, 1958. McMahon, W., Hill, C. M., and Koch, F. C. Greensalt: A New Preservative for Wood. Proceedings American Wood Preservers' Association. .38, 334, 1942. Milton, R., and Duffeld, W. D. Determination of Arsenic in Soils, Foods, Organic Compounds, Etc. Analyst. '61, 279, 1942. Phillips, L. S., and Baechler, R. H. A Review on Methods for Determination of Arsenic Boron, Chlorine, Fluorine and Zinc that Might be Useful in Wood Preservation. Rep. Forest Products Laboratory, Madison, Wisconsin. W. P.-58. 1961. Saltzman, B. E. Microdetermination of Chromium with Diphenyl Carbazide by Permanganate Oxidation: Improved Method of Oxidation and Color Development. Anal. Chem. ‘24, 1016, 1020, 1952. Sandell, E. D. Colorimetric Metal Analysis. Interscience Publishers, Inc., New York, 1944. Schulek, B., and Von Villecz, P. Die mabanalytische Bestimmung des Arsins in Gegenwart von Organischem Stoffen, Halogenen and Schwermetallen. Through reference Z. Anal. Chem. .16, 81, 1929. Smith, G. F. The Wet Ashing of Organic Matter Employing Hot Concentrated Perchloric Acid: The Liquid Fire Reaction. Anal. Chem. Acta. .5 (5), 397, 1953. Snell, F. D., and Snell, C. T. Colorimetric Methods of Analysis. Vol. II. D. Van Nostrand Company, Inc., New York, 1954. Ill. sill, II‘ | ill I'll-u l‘ I! It. I. I ‘llIlll I II. I ll‘lll I‘ll. [I ll", \ : t 37. 38. 39. 40. 41. 42. 43. 44. 45. 92 Strafford, N., Wyatt, P. F., and Kershaw, F. G. A Scheme for Photometric Determination of Minute Amounts of Arsenic, COpper, Lead, Zinc, and Iron (with Certain Other Metals) in Organic Compounds, e.g., Medicinals. Analyst. .19, 232, 1945. . The Separation of Small Amounts of Arsenic, Copper and Bismuth from Lead and Zinc by Means of Diethylammonium Diethyldithiocarbamate. Analyst. .l§,'624, 1953. Tanaka, T., and Hiiro, K. Spectrophotometric Determination of Arsenic with Quercetin. Bunseki, Kagaku. .12, 914, 1963. . Spectrophotometric Determination of Arsenic with Rutin. Bunseki, Kagaku. .12, 914, 1963. The Society of Analytical Chemistry, England. 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APPENDIX I List of Reagents Used in Volumetric Analysis Reagents Used in Volumetric Analysis of Arsenic l) Hydrochloric acid, concentrated. 2) Hypophosphorous acid, 50 per cent. 3) Sulfuric acid, concentrated. 4) Potassium bromate, 0.1000 normal--dissolved 2.784 grams of pure dry potassium bromate in redistilled water and made up to 1.000 liter in a volumetric flask. 5) 4ethy1 orange--0.1 per cent water solution. Reagents Used in Volumetric Analysis of Chromium (Hexavalent) 1) Phosphoric acid, 85 per cent. 2) Barium diphenylamine sulfonate solution-—0.20 gram barium diphenyl sulfonate made up to 100 ml. with water. 3) Ferrous ammonium sulfate--su1furic acid solution--) 140 grams of ferrous ammonium sulfate Fe(NH4 ) 2(SO 2. 6H 0 and 25 m1. of concentrated sulfuric ac1d 2madé) up to one liter with redistilled water. 4) Sulfuric acid 1:1 solution--one volume of concen- trated sulfuric acid was slowly added with constant stirring to one volume of water. Cool before use. 5) Potassium dichromate solution, 0.2000N--weighed 9.807 grams of potassium dichromate into a one liter volumetric flask and adjusted the volume to exactly 1.000 liter with redistilled water. Reagents Used in Volumetric Analysis of Copper 1) Ammonium hydroxide, concentrated. 2) Hydrochloric acid, concentrated. 3) Alcohol, ethyl. 4) Potassium iodide solution, 20 per cent-~dissolved 20 grams of potassium iodide KI in 80 ml. of water. 93 5) 6) 7) 9) 10) 11) 12) 94 Sodium thiocyanate solution, 20 per cent-- dissolved 20 grams NaCNS in 80 m1. of water. Starch indicator--Made a paste of one gram soluble starch in about 5 m1. of water, add 100 ml. water to it and boiled for one minute with stirring. One drop chloroform was added after the starch solution was cooled. Acetic acid, glacial. Copper shot. Nitric acid, concentrated. Urea solution, 5 per cent--dissolved 5 grams urea in 95 ml. redistilled water. Sodium thiosulfate solution, 0.1N.--dissolved 24,85 grams of Na S 03'5H O in redistilled water and added 1.0 gram 8f NaZCO3 as a preservative and diluted to one liter. Sodium thiosulfate solution, 0.01N. diluted exactly 50 m1. of the standardized 0.1N sodium thiosulfate solution to exactly 500 ml. with freshly prepared redistilled water. II It .. l. Illlllillill'lltl I‘ll]