fl ) l “llMllWl W: I I 114 226 THS_ AN {NV‘ESTIGATION EN'E'O' THE INCLUSION OF FUCHSIN IN BRIGHT NICKEL DEPOSITS THESIS FOR THE DEGREE OF M. S. MECHIGAN STATE UNIVERSITY OTTO JOSEPH KLINGENMAIER £958 \ rm-Wwwwb w-“v \ r I '7' 3*. n ' \ _" A“ I \ i s._ f u" . K: . y... mg) n ._,- U mv c131”: y ‘r- xxx-:9, 253w 1-min— AN INVESTIGATION INTO THE INCLUSION OF FUCHSIN IN BRIGHT NIJRSL DEPOSITS By Otto Joseph Klingenmaier A THESIS Submitted to the College of Science and Arts of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1956 ACKNOWLEDGEMENT The author wishes to express his sincere appreciation to Dr. J. L. Dye, Assistant Professor of Physical Chemistry, for his guidance and assistance throughout the course of this investigation. 11 AN INVESTIGATION INTO THE INCLUSION OF FUCHSIN IN BRIGHT NICKEL DEPOSITS By Otto Joseph Klingenmaier AN ABSTRACT‘ Submitted to the College of Science and Arts of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1956 Approved ABST CT The purpose of this investigation was to determine whether a brightener of the second class was included in nickel deposits during the process of bright plating. If the brightener could be recovered from the dissolved nickel, an examination was to be made of the effect of brightener concentration and current density on the amount included. The presence of brightening agents, or products thereof, in the deposit seems a logical assumption since these com— painds take part in the mechanism of bright plating. Second class brightening agents are very effective addition agents; their concentration in the plating solution may range as low as one milligram per liter. It was there- fore important to use a compound that could be detected in minute amounts. Fuchsin (also known as rosaniline hydrochloride), which is a member of the tri—phenyl methane family of dyes, was chosen as the second class brightening agent because it could be extracted from nickel solutions with methyl ethyl ketone and detected spectrophotometrically in concentrations as low as 50 micrograms per liter. A further study was made of the properties ofihis dye. The oxidation of fuchsin was found to occur easily and apparently irreversibly. The reduction of fuchsin, however, proceeded slowly with the formation of an erratic and iii unstable_type of solution. This irregular behavior was suspected to be due partly to the presence of a free radical. The existence of the free radical at the drOpping mercury electrode was confirmed from the equation of the cathodic polarographic wave of fuchsin. Excellent deposits were produced from bright nickel solutions containing from one to three milligrams per liter of fuchsin. Depositions were generally made from one liter amounts of solution upon buffed and passivated nickel cathodes. When the effect of current density was studied, the electro- deposits were prepared from a Hull Cell, which held 250 ml. of plating solution. In order to analyze for the included fuchsin, the nickel deposits were detached from the base panel and dissolved in concentrated (36 percent) hydrochloric acid. After the pH values of these solutions were raised to 4.5, the dye was extracted with methyl ethyl ketone. DeSpite an apparent loss of fuchsin in the dissolution procedure, the analyses of the detached deposits produced definite trends: 1. The amount of fuchsin that was found in the deposit increased with its concentration in the solution. 2. The presence of another brightener of the second class, zinc. sulfate, in the plating solution seemed to decrease the amount of fuchsin in the deposit. iv 3. As noticed from the Hull Cell depositions, an increase in current density brought about a decrease in the quantity of fuchsin recovered from the deposit. The percent of fuchsin included in the nickel deposits was very low (about 0.01 percent). Ratios of fuchsin.molecules to nickel grains were calculated and from the values obtained, it appeared that during the mechanism of bright plating these organic molecules may attach only at special points on the cathode—~grain edges and corners of high current density. TABLE OF CONTENTS CHAPTER Page I . INTRODUCl‘ION o o o o o o o o o o o o o o e o o 1 II. EXPERIMENTAL . . . . . . . . . . . . . . . . . 5 Selection of Fuchsin as the Second Class Brightener . . . . . . . . . . . 5 General PrOperties of Fuchsin lmportant to the Problem. . . . . . . . . . . . . 6 Reduction of Fuchsin. . . . . . . . . 12 Electrolytic Oxidation of Fuchsin . . . 21 Preparation and Purification of the Nickel Stock Solution . . . . . . . . 28 Preparation of the Nickel Base Panels . . 30 Preparation of the Detached Deposits . . 32 Hull Cell Depositions . . . . . 35 Determination of Fuchsin in the Nickel Plating Solution. . . . . . . - 37 Determination of Fuchsin in the Detached Nickel Deposits . . . . . . “0 Dissolution of the Nickel Deposits. . . 40 Recovery of the Fuchsin from the Acid SOlution O O O O O O I O O O 0 I O O O “3 III. RESULTS 0 O 0 O O O O O O O O O O I O O O C O O “8 Effect of Fuchsin Concentration on the Amount of Dye Recovered from the Deposit. #8 Amount of Fuchsin Recovered from Con- secutive Depositions in the Same Solution. 51 Influence of Current Density on the Quantity of Fuchsin Included in the De- posit . . . . . . . . . . . . . . . . . . 56 IV 0 COINCL‘USIONS O O O O O O O O I O I O O O O O O O 59 v I SUIVIPIA BY 0 O O O O O O O O O O O O O O O I O 0 61+ LIST 0? REFERENCES . . . . . . . . . . . . . . . . 67 vi TABLE II. III. IV. VI. VII. VIII. LIST OF TABLES Page Recovery of Fuchsin from Hydrochloric Acid Solutions Subjected to Various Conditions of Time and Temperature . . . . . . . . . . . . #6 Effect of Reduction with 1.2 Grams of Nickel andfiifteen ”‘. of Concentrated Hydrochloric Acid on 40 Nicrograms of Fuchsin . . . . . . . 47 Effect of Fuchsin Concentration in the Plating Solution on the Amount of Brightener Recovered from the Deposits . . . . . . . . . . . . . . . 49 ‘Data Obtained in Consecutive Depositions from Two Bright Nickel Solutions Containing De- creasing Amount of Fuchsin . . . . . . . . . . 52 Data Obtained in Consecutive Depositions from a Bright Nickel Solution Adjusted to Similar Initial Fuchsin Concentrations. . . . . . . . . 55 Data Obtained in Consecutive Depositions from a Bright Nickel Solution Containing an Original Amount of 0.44 gram of Zinc Sulfate. Fuchsia Concentration Adjusted to Similar Initial Values Prior to Each Deposition . . . . . . . . 55 Distribution of Fuchsin in Hull Cell Deposits . 58 Distribution of 100 Micrograms of Fuchsin in One Gran] of NICkel O O 0 O O O O O I O O O 0 O O O O 63 vii LIST OE ILLUSTRATIONS FIGURE 1. 10. ll. Absorption Spectrum in the Visible Region of Fuchsin in Water and in a Methyl Ethyl Ketone Extraction . . . . . . . . . . . . . . . . Absorption of Light at a Wavelength of 5A5 mu. as a Function of the Concentration of Aqueous Fuchsin Solutions . . . . . . ... . . . . . . . . Effect of the Hydrogen Ion Concentration upon the Light Absorption of Fuchsin Solutions . . . . Cathodic Polarogram of Fuchsin .... . . . . . . . Test for the Reversibility of the Equation of the Cathodic Wave for Fuchsin . . . . . . . . . . . . Electrochemical Destruction of Fuchsin in a Boric Acid Solution Adjusted to pH Value of 2.8 . . . . Absorption Spectrum in the Infra-Red Region of Fuchsin in Chloroform . . . . . . . . . . . . . . Drawing of the Hull Cell Showing Current Density Zones on the Cathode for Two Amperes Total Current 0 O O O O O O O O O O O I O O O O O O O 0 Calibration Curve for the Determination of Fuchsin in Nickel Solutions by Extraction with Methyl Ethyl Ketone . . . . . . . . . . . . Amount of Fuchsin Found in the Deposits as a Function of the Average Brightener Concen» tration in the Plating Solution . . . . . . . . . Effect of Average Brightener Concentration on the Amount of Fuchsin Recovered from Two Series of Consecutive Depositions. . . . . . . . . . . . viii ll 15 I7 23 26 36 39 50 53 CHAPTER I INTRODUCTION This investigation was carried out to determine whether a brightener of the second class is included in the nickel deposit during the process of bright plating. In addition, if the brightener could be recovered in its original form from the dissolved nickel, a study was to be made of the effect of brightener concentration and current density on the amount included in the deposit. The composition of bright nickel baths is both varied and complex. Along with the three normal constituents i.e., nickel sulfate, nickel chloride, and boric acid, the solution may contain.organic and inorganic twightening agents of two classes plus a wetting agent. In a review of nickel plating, Pinner gt a; (l) divide brighteners into two classes. The types of compounds included in these classes may be summarized as follows: Brighteners of the first class consist of cobalt salts and also organic componds that have a =C--SO‘H group in the molecule. Included in this class are the aryl sulfonamides, sulfonimides, polysulfonates, and sulfonic acids. Second class brightening agents include: (1) ions of metals such as zinc, cadmium, and lead-—which have a high hydrOgen overvoltage in acid solution, (2) organic compounds that containIC=O,;C=C:-C;C;-N=Ng-N=O, or:C=N-groups, and (3) a family of dyes containing the:C=Nebond of which the amino poly-aryl methanes are the most important. First class brighteners when added to a conventional nickel bath will not necessarily produce a bright plate but may merely cause a grain refinement in the deposit. Second class brighteners when used alone yield bright but brittle and highly stressed deposits. Moreover, their concentrations are very critical. However in combination with a brightener of the first class, greater amounts of the second class brightening agent can be tolerated. A less brittle deposit and also one with maximum smoothness and brightness is then produced (1). Although it is possible to classify brightening agents into a few distinct groups, no clear understanding exists on how these componds act to produce a bright deposit. Most of the bright nickel deposits are laminated structures con- sisting of thin layers parallel to the cathode surface. This stratification is eXplained by one theory (2) as an indication that the process of deposition is cyclic or inter- mittent. According to this theory, during each cycle there may be a build-up of organic molecules at the cathode surface until sufficient electrode potential has been reached to cause deposition. As a bright nickel deposit builds up at the cathode, a gradual decrease occurs in the concentration of the second class brightening agent. Decomposition products account for some of this loss. Since the brightener takes part in the mechanism of plating, it seems reasonable toassume that the remainder of this decrease in concentration would be due to inclusion of the material or its products in the deposit. The presence of carbonaceous matter in electrodeposited metals of the iron group has been reported by many previous investigators. Avery and Dales (3) found that iron depo~ sitions from solutions containing ammonium oxalate and citric acid held from 0.15 to 0.5 percent of organic material. Foerster (4) and Madsen (5) believed that the presence of this organic material in iron and nickel deposits was due to colloidal co-precipitation at the cathode. This viewpoint was Opposed by Skrabal (6) who showed that carbonaceous matter liberated by the dissolution of an anode, consisting of contaminated oxalate-iron, will not again be deposited at the cathode. Another explanation for the presence of carbonaceous material was offered by Lambris (7),who suggested that these products were due to gas reactions catalyzed by the cathode in which the formation of acetylene was an intermediate step. This point of view was also shared by Froelich (8), who used a complex oxalate electrolyte in the deposition of nickel. A range of one to 2.5 percent of carbonaceous material was found to be present in the deposit, and from the characteristics of the residue he concluded that the carbon was not in the elementary state. More recently, Brenner gt‘gl (9) have determined the carbon and sulfur contents of electrodeposited bright nickel. The concentrations of these elements in the deposit were found to range from 0.02 to 0.08 percent. A search of the literature fails to disclose any successful investigations as to the identity of these organic inclusions. CHAPTER II EXPERIMENTAL S S o C s B The problem of recovering a second class brightener from a nickel deposit is increased by the exceedingly small amount that is used in the nickel solution. Since this type of compound is a very effective addition agent, its concen- tration in the plating solution may be as low as one milligram per liter. Analyses for the brightener on aliquot portions of such solutions or on nickel deposits prepared from them would involve the detection of very small quantities, some possibly as low as 25 micrograms. Such analyses could probably be best carried out by means of a spectrophotometric procedure. The amino tri-phenyl methane dyes are employed in many bright nickel baths as second class brighteners. A member of this family, fuchsin, was available in ample amounts for use in the investigation. Because of the intense red color of its solutions, application of a spectrophotometric procedure in the detection of minute amounts of the dye seemed very promising. Accordingly, an examination was made into some of the properties of fuchsin. General Properties of Fuchsin Important to the Problem Fuchsin is also known by the names of magenta and rosaniline hydrochloride. Its molecular and graphic formulas are shown as follows: NHz Fuchs in . E 02.:N3201 . C20 20” 301 . ' CH 3 NHZ The fuchsin used in this investigation was a certified biological stain, produced by the National Aniline Company and distributed by Eastman Kodak Company. Although dye con- tent was listed at 95 percent, the substance may have con- tained some of the non-methylated compound--pararosaniline. The dye is moderately soluble in hot water and separates upon cooling as the salt containing four moles of water of hydration. In an effort to increase its purity, the fuchsin was recrystallized twice in this manner. A standard solution at a concentration of 0.1 gram per liter was prepared from the recrystallized fuchsin. Aliquot portions of this standard were used in the preparation of one liter solutions containing as little as 50 micrograms of the dye. THE Fuchsin imparts a brilliant red color to its solution. The absorption Spectrum in the visible region of 0.5 milli- gram of fuchsin per liter of redistilled water (pH = 6.5) is shown in Figure 1 as curve a. Minimum transmittance of light occurreden;a wavelength of 545 millimicrons. The molecular extinction coefficient was calculated to be equal to a value of 65,000. The dye was found to be quite soluble in alcohol and in methyl ethyl ketone. Using the latter, it was possible to obtain nearly 100 percent extraction of the fuchsin from aqueous solutions. An addition of sodium chloride was usually made in order to decrease the number of extractions 'by a salting out effect. The absorption spectrum in the visible region of a methyl ethyl ketone extraction, which contained 0.5 milli- gram of fuchsin per liter, is presented in Figure l as curve b. Minimum transmittance occurred at a wavelength of 5&8 millimicrons. In this solvent the molecular coefficient was equal to a value of 91,000. The spectra in Figure l were recorded with a Beckman Automatic Recording Spectrophotometer. Model DK-Z. The amount of absorption by fuchsin in aqueous solutions was found to be a function of both the concentration of the dye and the pH value of the solution. Reference to Figure 2 shows that at constant pH, a graph of increasing concen- tration versus Optical density of the solution gave a I.“ ‘— V 7 7R/i/‘J5M/ 7' TANG, Ex F2390, as oo- 95 7S a __._._._. .__._.......J l b i F—_—” .. I l l i I ‘L__._.____. . I ______.z i i I 5.,qu ________ l I “—“"T 1:148 l I I | 7 7 l 500 525 sec MM 5/5 L 5 N6 7H " M/é Z /M/C/?O//5 Figure l. The absorption spectrum in the visible region of 0.5 mg. fuchsin per liter of (s) redistilled water at a pH of 6.5 end (1)) s methyl ethyl ketone extraction. 1H5 :3... .1... , . «.Hsunrw ‘1. Ml‘l 1104....“ 0.42., 1H... . 9F; ‘ . . I‘ m ..‘l‘luw. «snug-.11. ._ 5 . oar/CAL o.6-——-——— _ ...... i 2 3 1, M/LL/GHAMS FUCHS/N PEA" L/TEA“ Figure 2. The absorption of light at a wavelength of 545 mu. as a function of the concentration of aqueous fuchsin solutions. KNEE fled LIE L [7,... 3., i .. A? . .. h. . . ‘ . ...» s .LIu.‘iE.r.61.LE.g C 10 straight line with zero intercept in agreement with Beer's law. The effect of a change in pH upon light absorption is shown in Figure 3. Maximum and nearly constant optical densi- ties were obtained in the range of pH from 3.5 to 5.0. The addition of alkali to an aqueous solution of the dye results in the gradual formation of the hydroxy derivative and the loss of color (10): NH2 NH2 C: .NH281+ NaCl HBO-COME + NaCl .0113 CH3 “Hz 2 This carbinol base may be converted back into the red dye upon the addition of a mineral acid such as hydrochloric (10). As the pH of a fuchsin solution was lowered with hydro- chloric acid, the color changed gradually from red to violet. At a pH range of 2.0 to 1.5 the color of the solution dis- appeared entirely or turned to a light yellow. The loss of the intense red color and simultaneous disappearance of the characteristic absorption spectrum is attributed to the formation of the tri-acid derivative of fuchsin (10): 7TH! OPT/CAL DEA/S/T)” ll meg—m.— a.“ 0.20 0.15 0.05 i ' i 3 s PH‘VALL/E Figure 3. Effect of the hydrogen ion con- centration upon the light absorption of 1 mg. per liter fuchsin solutions. 12 .CH “'3 3 31‘ The tri-acid derivative was changed back into the red dye by the action of either sodium hydroxide, sodium carbonate, or sodium bicarbonate on the acid solution. In all these cases, the concentration of the fuchsin was three milligrams per liter or less. The first example of any irregular action of fuchsin or its derivatives occurred when nickel carbonate was used to neutralize acid solutions of the dye. In no instances could the red color of fuchsin be regenerated or extracted into the methyl ethyl ketone. Reduction of Fuchsin It has been reported (11) that the reduced form, bis-p— amino-phenyl-m-tolyl methane, is produced when an aqueous solution of fuchsin is treated with nickel or zinc plus hydrochloric acid: NHBCI NHBCl c=.=NH201+ N1+ 2Hc1—->; H-C-.NH301 + N1012 . H3 ‘H3 VHBCl H3Cl 'INI u "9..., v.1“0‘ 13 This compound was prOposed by Lind §j_gl,(ll) as a brightener of the second class and is used in some commercial bright nickel baths. Numerous attempts were made in this investigation to employ reduced fuchsin as the second class brightener. Although excellent deposits were produced from nickel solu- ions containing this addition agent, a suitable method could not be develOped for its analysis. The reduced fuchsin was prepared by treating twenty milligrams of fuchsin in 75 ml. of water with 25 ml. of concentrated (36 percent by weight) hydrochloric acid and three grams of powdered nickel. Additional nickel was added as needed, and the reduction was continued until the pH had risen to a value of 2.0. The volume of the solution was adjusted to 250 m1. so that a 25 m1. sample would contain an amount equal to two milligrams of what was originally fuchsin. When such an aliquot was diluted to a liter and the pH adjusted to 3.2 (the operating value for the bright nickel plating solutions), the color of fuchsin gradually returned. The time of reduction was lengthened to a week and even zinc was employed as reductant in an effort to obtain complete conversion of the fuchsin to the reduced form. In all cases, whenever the pH of these solutions was brought above 2.0, some of the fuchsin was regenerated; over a period of days and weeks the amount increased continuously. lb The transformation into fuchsin, although spontaneous, was not rapid nor was it ever complete. To obtain a clearer picture of this reaction, polarographic waves of fuchsin and reduced fuchsin solutions were determined at the drOpping mercury electrode of a Sargent Model XXI PolarOgraph. A one millimolar solution of fuchsin, containing 0.1 normal potassium chloride as supporting electrolyte, was used to obtain the cathodic wave shown in Figure 4. The half-wave potential was equal to a value of -0.64 volts versus the saturated calomel electrode. Anodic polarograms of reduced fuchsin solutions were also obtained. In preparing a typical solution, a 25 ml. sample containing 32 milligrams of fuchsin per liter was reduced for five hours with nickel in the presence of hydro- chloric acid. Immediately prior to polarographic analysis, the pH was raised to a value of 4.5 with sodium bicarbonate. PolarOgrams made of fuchsin solutions that had been reduced for longer periods of time also produced similar curves. No evidence could be found for the existence of an oxidation wave of reduced fuchsin corresponding to the cathodic wave of fuchsin. Thus it appeared that the electroactive material did not undergo reversible reduction and oxidation at the dropping mercury electrode. Sharp peaks were always observed at +0.07 volts versus the saturated calomel electrode in the anodic polarOgrams of reduced fuchsin. Because of its proximity to the anodic CURRENT - AWCA’O/IMPEREJ 15. 1.8..m___. .....i {id-1.):(AX‘ 1.3————-— —— r*arvsrofi is. 1' "a?“ I l I 0.8 I *——-—— I :1 : (TN I I I 0.3 I —‘—""‘—"‘ l TTI ‘ F T FTT:I;'\T“W‘ I I IE1 L E‘ , “004 -°.§ -0.6 .0,7 .0.8 Ede. v0L7’5 v5 5.0.5. Figure 4. Cathodic polarogram of a l milli- molar solution of fuchsin containing 0.1 N potassium chloride as supporting electrolyte. Instrument used: Sargent Model.XXI polarograph. l6 wave for mercury (+0.23 volts) further study of the nature of the peak was not attempted. According;to an equation derived by Heyrovsky and Ilkovic, the oxidation potential varies as a function of the current at any point of the polarographic wave: - 0.0591 i E — £1 -+ ....__. 10 g n 8 Id— 1 ' where 1d is the diffusion currentand i is the current at any point of the polarographic wave (minus residual current). A graph with the values of log __1_, against the corresponding applied potential of the microelegtrode should be a straight line having a slope of Engigl for a reversible reaction (12). Figure 5 is a test gor the reversibility of the equation of the cathodic wave for fuchsin. The straight line was determined by the least squares method and the number of elec- trons, n, taking part in the reaction was calulated to be equal to 1.06. The electron change was about one-half the theoretical amount necessary for the complete reduction of fuchsin and indicated the possible formation of the free radical: NH Cl NH3C1 C: .Wzm ‘* ° ‘* “Jr—"9 'C'HBQ .CH3 .CH3 NH3C1 ‘H Cl +1.o * +0.13 - ~+ +0.3 ._ a. -Q ’3 —‘ -mr’fl -I -1.r_\ 0 .S- ---- i 7? .y 54 '06?) 'e031:— -.=/38 APPUED PO TENT/AL‘I/OATS Figure 5. Test for the reversibility of the equation of the cathodic wave for fuchsin. l7 18 The existence of free radicals from the reduction of the triphenylmethane dyes was proposed by Conant £1; a}, (13). Conant and Bigelow later mentioned that: . . . the reduction product (or products) are not rapidly oxidized and no significant oxidation - reduction potentials can be measured by the usual methods. .The action of concentrated hydroch oric acid on the free radicals appears to cause the irreversible formation of a dimer isomeric with dissociable ethanes (14). The unstable character of the triphenylmethyl radicals ‘Wal pointed out by Gilman.(15). Some of the reactions that may take place are: polymerization, reduction, and oxidation Itastened or initiated by light, heat, or acids. Despite the apparent unstable behavior of the reduced ifuchsin solutions and the complications arising from the Iaossible existence of a free radical, a search was conducted for an oxidizing agent that would provide maximum trans- fkormation of the reduced fuchsin to fuchsin. Although previous investigators(]§ll6) list a number CNF oxidizing agents such as lead peroxide, manganese dioxide, potassium permanganate, or potassium chromate to be suitable fWar oxidation of reduced fuchsin, they also caution against lining an excess of the oxidant due to the oxidation of the f'uchsin itself. Due to the dilute nature of the reduced r'uchsin solutions used in this study, it was impossible to INPevent an excess of oxidant from being present. The amount (”F reduced fuchsin was generally in the order of 50 micrOgrams TH 19 per sample and such small quantities always seemed to be oxidized by strong agents beyond the desired value, apparently irreversibly. Anodic polarograms were run on solutions of fuchsin tfldat contained 0.l normal potassium chloride as supporting «electrolyte. Using the dropping mercury electrode, an in- cxrease in anodic current was observed starting at +0.14 twelts versus the saturated calomel electrode. The oxidation <>f mercury interfered with a study of the process. Oxidation sat a rotating platinum electrode produced a wave having a lialf-wave potential of +0.28 volts versus the saturated <3alomel electrode. 0f the various mild oxidizing agents that were tried :in.attempts to obtain only an oxidation of reduced fuchsin 1:0 fuchsin, the most consistent and reproducible results vvere obtained by the use of nickel formats. The procedure fellowed was to add a gram of nickel fkbrmate to a 25 ml. sample containing up to four milligrams EDEn-liter of reduced fuchsin and heat the solution to 90°C. jxhe presence of nickel formate caused the pH of the solution 130 rise from its former level of 2.0 - 2.5 to a value of Eibout 4.5. Methyl ethyl ketone was then used to extract the dye from the solution. Although the color of the dye did Ilot develop fully until a few hours after the extraction, tflie use of nickel formate always produced the maximum values (bf color intensity. 20 Analyses of reduced fuchsin samples from the same standard solution agreed closely with one another in the percent of fuchsin recovered. However, considerable variance was found to exist, when these results were compared against similar analyses from other reduced fuchsin standards. The percent of fuchsin recovered from four different standard solutions fell into the following ranges: 6h-65, 72-75, 78-80, and 87—90. This spread in fuchsin recovery could have been due to a difference in the degree of reduction and/or to the presence of an unstable substance. Other anomalous effects resulted from the reduced fuchsin solutions. For example, to simulate thejdissolution of a deposit, samples containing reduced fuchSin were treated with cut nickel foil and hydrochloric acid. When either sodium hydroxide or ammonium hydroxide was used to raise the pH value into the extraction range, the quantity of fuchsin recovered was found to be apparently greater thanthe amount originally in the solution. 0n the other hand if sodium bicarbonate was employed as the neutralizing agent, this effect was not produced. In another instance, a deposition was made from a bright nickel solution containing a definite amount of a reduced fuchsin standard. The subsequent analysis for fuchsin in the plating solution revealed a greater concen- tration of the dye present than what had originally been used in the preparing the reduced fuchsin standard. 21 The irregular and erratic behavior of the reduced fuchsin solutions could not be controlled nor could such a -degree of error and uncertainty be tolerated. Reduced fuchsin was therefore no longer employed as the second class brightening agent. Instead, the regular form of fuchsin was used. Electrolytic Oxidation of Fuchsin From the start, analyses of fuchsin from aqueous solu— tions had been both accurate and simple. However, it wps thought to be undesirable for use as a second class brightening agent. To test its effectiveness in a plating bath, a number of depositions were made from a liter of bright nickel solution that contained two milligrams of the dye. Excellent bright nickel deposits were produced. Moreover, no difficulties were encountered in the analyses for fuchsin from either new or used plating bath samples. The amount of fuchsin in the nickel plating solution gradually decreased as deposition of the nickel progressed. It was necessary to add additional amounts of fuchsin peri- odically to insure maximum brightness in the deposits. The decrease in fuchsin concentration during deposition lent support to the contention that the brightener was in— cluded in the deposit but also gave rise to the following pertinent questions: 1. Were electrode reactions reSponsible for part of this decrease in concentration? 22. 2. Which electrode contributed the greatest share toward destruction of the fuchsin? 3. Could any of the electrode products be isolated? Three experiments were conducted to help provide answers to these questions. In regard to the first query, a solution of two milli- grams per liter of fuchsin that had been adjusted to a pH value of 3.2 was subjected to a continued electrolysis. Ten grams of boric acid were added as a buffering agent. Agita- tion was provided by an electrically-driven stirring rod, which was located midway between two carbon electrodes. A current of 0.1 ampere was applied for approximately four hours. PeriOdically, a 25 ml. sample was removed and analyzed for fuchsin content. The concentration of fuchsin in the solution as a function of the amount of electricity passed is shown in Figure 6. The fuchsin dropped steadily in concentration as the electrolysis was continued; its characteristic red color changed gradually to light brown. To determine which electrode was responsible for the loss in color, a porous cup was used to separate the anode and cathode compartments. five hundred ml. of a solution equal in composition to that used in the previous electro- lysis served as the electrolyte. In this instance, a current of 0.2 ampere was applied to the carbon electrodes. rW‘C).8 3 e .1- M/Al/G‘ADAMS FUCHS/N p57? 1/7'5/9 H I» too Son 1200 COULOMBS 10A 35 [0 Figure 6. The electrochemical destruction of fuchsin.in a boric acid solution that had been adjusted to a pH value of 2.8. 23 24 Within half an hour the red color of fuchsin in the anode side had disappeared; a light brown tinge was now evident. A sample of the solution was analyzed for fuchsin, but no trace of the dye was found to be present. In the cathode compartment, however, the red color had remained at about the same degree of intensity. Only a visual check was made of the fuchsin in the catholyte because the dye had the tendency tol)ecome adsorbed into the porous cup. The polarity of the current was reversed and the elec- trolysis was continued for another half hour. Again the red color vanished in the anolyte. Subsequent analyses in- dicated that no fuchsin was present in either compartment. The results of the previous two tests seemed to indicate that the decrease in concentration of the fuchsin during a deposition may be due in large measure to oxidation of the dye at the anode. With the prospect of obtaining a sufficient amount of the oxidized material for purposes of identification, a solu- tion of 0.1 gram of fuchsin in 200 ml. of water was electro- lyzed at a current of 0.2 ampere. A few drops of hydro- chloric acid were added to aid conduction. Over a period of hours the color of the solution gradually changed to black. The electrolysis was continued for one hour after the last visible traces of red color had disappeared. In order to separate the large amount of carbon, which had becime detached from the electrodes, the supernatant 25 liquid was decanted from the residue, filtered, and divided into two parts. Chloroform extractions that were made on one sample were brown in color. Similar extractions on a fuchsin solution turned out red. Infra-red spectra of the unknown material and of fuchsin in chloroform were taken by means of a PerkinJHqu~ Model 21 Recording Spectrophotometer. The infra-red spectrum of fuchsin is shown in Figure 7. The spectrum of the unknown substance was practically identical to that of the fuchsin. Respective maximum and minimum points of transmittance occurred at the same wavelength. The only breaks in the curves that differed from each other by more than five percent were recorded at wavelengths of 6.25 and 9.27 microns. At these corresponding wavelengths, transmittances of 40 and 63 percent were obtained for fuchsin as against 51 and 73 percent for the unknown material. The remaining sample from the electrolysis was evapo- rated at room temperature to a black residue. An attempt was made to obtain the molecular weight of the material by the East method (17). Using camphor as solvent and acetanilide as solute, the Result constant for camphor was calculated to be 30. An addition of 0.7 milligram of the black residue to 0.0301 gram of camphor reduced the freezing point of the latter by 5°C. The molecular weight of the unknown substance thus appeared to be in the neigh- borhood of 230. 26 .aoposOHOSQOApoemm wsauaooom Hm Hove: soEHMIndxsom «use: uses—SamsH ..ahouoaoano ad sauces.“ no :3.“on contends: on» a.“ 8:93on ”3393QO 05... .m. easmdm %>\Q~\b\\< \<\ IKQENVM>VS> +2 Na OH m m a . “ _.__ :1- ON on om OOH JON 17/1 ..l/WS/VWU 1N33b’30’ 27 This figure, however, is not accurate nor can the determination be termed successful, for a reaction appeared to occur between the camphor and about one-half of the black solute--leaving the rest undissolved. Increasing the amount of camphor in the capillary tube did not decrease the percent of solute that remained insoluble. The remainder of the black residue was heated in a test tube in an effort to obtain the melting point. The material did not melt; a gas was evolved leaving a carbonaceous residue. 28 P o . ( P . o o the Niqgg] Stggk Solution The nickel stock solution used in the experimental work was a Watts type of the following composition: NiSOu.7H20 240 grams/liter 32 oz./gal. NiClz.6H20 45 grams/liter 6 oz./ga1. Boric acid 30 grams/liter 4 oz./gal. The plating solution was made up in a twenty liter pyrex glass container. The nickel salts and boric acid were dissolved in redistilled water, which was heated by a pyrex steam coil and agitated with mechanical stirrers. The solution was purified of metallic impurities in accordance with a method develOped by W. M. King (18). The first step in this procedure consisted of a high pH treatment. Nickel carbonate was added to the solution until the pH had risen to 5.5 - 5.6.‘ The agitated solution was kept at this pH and heated to temperature of 70 - 75°C for a period 24 hours. At the end of this time, it was filtered thru a Buchner funnel using paper and a one-fourth inch layer of asbestos. The pH of the solution was then adjusted to a value of 3.2 with c.p. grade sulfuric acid. The solution was further-purified by electrolytic treat- ment. An anode of electrolytic nickel was placed in the solution opposite a corrugated cathode. This cathode was prepared by making alternate 90° bends at 1: in. intervals along a strip of steel tin can stock measuring 7 in. by 14 in. 29 The solution was kept well agitated, and its temperature was maintained at 70 - 75°C. A current density of five amperes per square foot of projected area of cathode was applied for 100 ampere hours per gallon of solution. According to W. M. King (18), such a procedure removes heavy metal concentration to spectroscopic traces. Upon completion of electrolytic purification, organic impuritieswere removed by the addition of 7.5 grams per liter of activated charcoal. The solution was agitated vigorously and kept at a temperature of 70 — 75°C for a period of 24 hours. At the end of this time, the carbon was allowed to settle and the solution was filtered twice through filter paper on a Buchner funnel. The purified solution was stored in a twenty liter glass bottle. The composition of the bright nickel solution used in the preparation of the detached deposits is as follows: Nickel sulfate . 240 grams/liter Nickel chloride 45 grams/liter Boric acid 30 grams/liter Sodium naphthalene disulfonate 4.5 grams/liter Sodium lauryl sulfonate 0.1 grams/liter Fuchsin 0.5 - 3.0 milligrams/liter In one set of depositions,the above composition was modified by the addition of 0.44 grams of zinc sulfate, another brightener of the second class. 30 In the preparation of the baths with organic addition agents, necessary amounts of the first class brightener, sodium naphthalene disulfonate, and the anti-pitting agent, sodium lauryl sulfonate, were added toihe purified Watts type stock solution. The solution was filtered, and the pH was adjusted with five normal sulfuric acid to a value of 3.2. The required amount of second class brightener was then added from a previously prepared standard solution. All pH measurements throughout this investigation were made with a Beckman Model G pH meter, which was checked with a pH 7 buffered solution. P e 10 o t e N e B e P Brass sheet stock of 0.020 in. thickness was used in the preparation of the nickel plated panels. inuamajority of the panels were cut to a size of 3.5 in. by 2.4 in.; the remainder measured 3.75 in. by 2.5 in. The corner of'each panel was stamped with a numbering die to facilitate later identifica- tion.. The parts were then buffed to a mirror finish with "Tripoli" buffing compound (a product of the Hansen-Van Winkle-Munning Co., Matawan, N. J.), degreased with carbon tetrachloride, and put through an electrocleaning cycle pre- patory to plating. The cleaner composition and conditions employed, similar to that used by J. M. Tobin (19), is as follows: 31 Sodium hydroxide 21 grams/liter 2.8 oz./gal. Sodium metasilicate 15 grams/liter 2.0 oz./gal. Tri-sodium phosphate 18 grams/liter 2.“ oz./gal. Sodium carbonate 6 grams/liter 0.8 oz./ga1. Temperature 90 - 95°C 194 - 203°F 2 Current density 8.6 amp./dm. 80 amp./ft? The cleaner was made up in a four liter pyrex beaker and was replaced with a new solutiqn when imprOper cleaning was observed. A circular strip of steel tin can stock served as the cathode. The brass panel was made the anode and the current passed for three minutes. The panel was rinsed in running water and if satisfactorily cleaned, was devoid of water breaks. After electrocleaning, the panel was given an acid etch in 20 percent hydrochloric acid for twenty seconds, followed by two running water rinses-~the last one being dis- tilled water. Nickel plating was carried on in rectangular pyrex glass Jars, which held one liter amounts of the nickel stock solution. The pH of the solution was adjusted to 2.2 with five normal sulfuric acid. A copper water bath heated by a bunsen burner kept the temperature of the solution at 55:190. An anode of electrolytic nickel, 1.5 in. wide, 0.4 in. thick, and 6 in. long was covered with a nylon bag and was suspended in the solution at one end of the Jar. The brass panel was made the cathode and was immersed in the solution one-fourth 32 inch from the other side. Agitation of the solution was provided by an electrically driven, low pitch propeller- type, glass stirring rod rotating at two hundred revolutions per minute. The stirring rod was located equidistant between the anode and cathode with the blades at the same level as the midpoint of the cathode. The deposition of nickel was initiated immediately after the cleaning operation and continued for 20 minutes at a current density of 12 amperes per square foot. At the completion of plating, the panel was rinsed in water, dried, and stored in a desiccator until used for the preparation of the detached bright nickel deposits. P i e D e De Nickel deposits that have been plated upon a buffed and passivated nickel or steel surface do not adhere tightly to the base metal and can be easily removed. The 3.5 in. by 2.h in. brass panels that had been coated with a dull nickel deposit were buffed to a very smooth, bright finish using "Acme Pink Finish" (a product of Hanson- Van Winkle-Munning Company, Matawan, N. J.). A line was scribed across the narrower face of each panel one-half inch from the stamped end. Later immersion into the plating cell was made up to this mark and provided a total plated area of 0.1 square foot. 33 In order to obtain an easily removable deposit, the ‘buffed metal was treated in a manner similar to that described in theses by J. M. Tobin (19) and Russell Fay (20). The ;panel was wiped off with carbon tetrachloride to remove any adhering buffing compound. It wps cleaned electrolytically in an alkaline cleaner, similar in composition to that used jpreviously in the ”Preparation of the Nickel Base Panels." Two liters of this solution were made fresh weekly. A circular strip of steel tin can stock was used as the cathode. The buffed panel was made the anode at a current density of 80 - lOO amperes per square foot. The temperature of the cleanervvas kept at 90 - 95°C. To produce a uniformily passivated surface, the panel 'was alternately electrocleaned and dipped into a 20 percent Ihydrochloric acid solution. A typical run was made in the following manner: Water 20 percent Water 'Cycle Electrocleaner Rinse HCl Rinse l 2 minutes 1 minute 20 seconds 1 minute 2 1 II 1 n 2 0 II 1 ll 3 20 seconds 1 " 5 " l " 1+ 20 0| 1 II 1 II 1 u Following the fourth cycle, the panel was rinsed with dis- tilled water, dried, and weighed. All bright nickel depositions with the exception of the Hull Cell determinations were made from solutions of one liter. The organic type solution containing both fuchsin and 34 zinc sulfate, which was first used as the electrolyte, was <3perated at a current density of 32 amperes per square foot. {The remainder of the depositions, however, were Operated at .a.current density of 24 amperes per square foot from bright :nickel solutions containing only fuchsin as the second class ‘brightening agent. With the exception of anode bags, the equipment employed was identical to that used in the Watts nickel depositions. .Due to the adsorption of fuchsin onto the nylon cloth, no covering was placed over the nickel anode. Contamination of the deposit by the liberated anode particles was kept at a xninimum by positioning the stirring rod equidistant between the anode and cathode and 1.5 inches below the surface of the solution.’ This permitted the anode particles to settle to the bottom of the plating cell. Up to four deposits could be plated successively from the same solution without the occurrence of noticeable pitting. The passivated nickel panel, held by a clip, was immersed into the bright nickel solution up to the scribed line and at a distance of one-fourth inch from the wall of the jplating cell opposite the anode. The current was applied for one-half hour. At the completion of the required time of plating, the panel was removed from the solution, rinsed thoroughly with tap and distilled water, and dried. It was then reweighed to determine the amount of nickel deposited at the cathode. 35 The bright nickel deposit was removed by filing away the edges of the panel until the base metal was exposed. By flexing the panel slightly, the deposit was loosened so that it could be pulled off. The more tightly adhering deposits were removed with the aid of a razor blade. In this manner, it was possible to recover approximately 90 percent of the deposit. The detached nickel foils, which measured between 0.0015 and 0.002 inches thick, were rinsed successively with methyl ethyl ketone, tap, and distilled water. They were dried, weighed, and stored until analyzed for fuchsin content. Hull Cell Depositions A number of bright nickel deposits were also prepared from separate 250 m1. amounts of bright nickel solution. A Hull Cell, whose dimensions are given in Figure 8, was used as the plating cell. Because of the definite size of the container, a slightly larger cathode was needed. These panels measured 3.75 in. by 2.h in. and were also prepared with a buffed and passivated nickel surface. The anode con- sisted of two pieces of electrolytic nickel, 2.5 in. by 0.75 in. by 0.25 in., which were held by clips to the side opposite the cathode. Each deposition took place at a current of two amperes and lasted for 20 minutes. During the depositions, the n 5" >/ Figure 8. Drawing of the Hull Cell showing current density zones on the cathode for two amperes total current. 36 37 solution was agitated by a centrally located stirring rod and was kept at a temperature of 55 : 1°C. A wide current density range is obtained in the Hull Cell because of the geometric arrangement of the cathode relative to the anode. The current density at any point on the cathode can be estimated by the equation, A = c(27.7 - 48.7 log L) where A is the current density, C is the current, and L is the distance in inches from the high current density edge (21). Five current density ranges, 0 - 15, 15 - 40, 40 - 80, 80 - 120, and greater than 120 amperes per square foot, were arbitrarily chosen for separate study. The distance along the cathode, L, was then computed at which these current den- sities were effective. Each of the detached deposits were cut into five sections, as shown in Figure 8, corresponding to the chosen current density areas. The nickel deposits from the similar current density ranges were combined and these five samples were analyzed separately for fuchsin. De e m t on of Fu 8 in e Nicke Plat 301 t o SpectrOphotometric detection of fuchsin was not possible in the presence of nickel ions because of the high absorption of the latter. It was feasible, however, to extract the brightener from the nickel solution with methyl ethyl ketone when the pH value of the solution was in the range of 3.5 to 5.5. Nickel formate was used to raise the p value to the extraction range. Its presence also produced a secondary effect; that of saturating the nickel solution with a salt and thus reducing the number of extractions necessary to remove the fuchsin. The following procedure was devised for the analysis of fuchsin in the nickel plating solution. A 25 m1. sample of the bright nickel solution was heated with 1 gram of nickel formate to 90 - 95°C. The solution was cooled and trans- ferred to a 125 ml. separatory funnel. Successive small portions of methyl ethyl ketone were shaken with the solution to extract the dye. Whenever the fuchsin concentration was less than 2.5 milligrams per liter, a total of 25 m1. of extractant was used. With larger fuchsin concentrations, 50 ml. of methyl ethyl ketone were necessary to remove the dye from the nickel solution. The optical density of the methyl ethyl ketone ex~ traction at a wavelength of 5h8 millimicrons was determined with a Beckman Model DU Spectrophotometer. The calibration curve shown in Figure 9 was obtained by analysing nickel solutions containing known amounts of fuchsin and plotting the fuchsin concentration versus the SpectrOphotometer reading. M/LL/GPAMS FUCHS/N PEP L/TEA" l i l l 0.2 04h ms 0.8 OP T/CAL DEA/677% Figure 9. Calibration curve for the determination of fuchsin in nickel solutions by extraction with methyl ethyl ketone. Instrument used: Beckman Model DU Spectra hotometer at 548 mu wavelength. (25 m1. sampleaog 39 40 In order to develOp a successful analysis for fuchsin in the nickel deposits, it was first necessary to dissolve the nickel without causing destruction or radical alteration of the organic material. The resulting solution then had to be treated and conditions adjusted so that the colored species of fuchsin could be extracted with methyl ethyl ketone. Dissolution of the Nickel Deposits Three methods were investigated for dissolving the de— tached bright nickel deposits. d s o The nickel foil was made the anode and was immersed in 100 ml. of Watts nickel solution, which was kept in a porous cup. The cathode consisted of a circular steel strip. Water that had been adjusted with dilute sulfuric acid to pH value of 2.2 and buffered with boric acid was used as the catholyte. A current of 100 milliamperes at 2.3 volts was applied to the electrodes until the nickel foil had dissolved. Dissolution of the sample took ap- proximately eight hours. The anolyte was filtered and then analyzed for fuchsin in the manner described under "Determination of Fuchsin in the Nickel Plating Solution". Fuchsin could not be detected in the sample. However, gradually increasing optical densities of the extractant were noticed as the wavelength of the light 41 was decreased from 500 to 350 millimicrons. This did in- dicate that some material, possibly an oxidation product of fuchsin was being extracted from the nickel solution. Daggolgtion p1 Classen's :eagent. A mixture of cupric ammonium chloride and ferric chloride solutions is called Classen's reagent. It was used by Froelich (8) to dissolve nickel deposits without the production of nascent hydrogen. Twenty ml. of Classen's reagent, which contained 120 grams per liter of cupric ammonium chloride and 200 grams per liter of ferric chloride, were added to a detached nickel deposit that had been cut into small pieces. Later additions of the reagent brought the total amount added to 60 ml. By maintaining a temperature of 60 - 70°C, one gram of nickel was dissolved in four hours. At the end of the dissolution, the pH value of the solution was equal to 2.0. It was raised to a value of 4.5 by the addition of sodium bicarbonate. The supernatant liquid was decanted from the precipitate of copper and iron hydroxide. An extraction performed on this solution with methyl ethyl ketone did not reveal any trace of fuchsin. A second bright nickel deposit was dissolved in a similar manner to the first. The supernatant liquid again was decanted from the precipitate after the pH value had been raised to u.5. The pH of this solution was then lowered to a value of 2.5. One gram of nickel formate was added and the solution was heated to 90°C. Upon cooling, the 42 solution was shaken with methyl ethyl ketone. Again as before, fuchsin could not be detected in the extract. A number of other modifications utilizing Classen's reagent also were unsuccessful. Further work on this method was dropped when encouraging results were obtained in the following procedure. D l o o - d d. The only successful method that was found with at least partial recovery of the included fuchsin was to dissolve the detached nickel deposit in hydrochloric acid. The nickel foil, weighing about 1.2 grams, was cut into small pieces and dissolved in 15 m1. of concentrated (36 percent by weight) hydrochloric acid. The dissolution took from two to three weeks when kept at room temperature and only four hours if intermittent heating to 70 - 80°C was used. The majority of the nickel deposits were dis- solved under the latter condition. At the completion of the dissolution, the pH value of the acidified nickel chloride solution was raised to the range of 2 - 3 by the addition of sodium bicarbonate. One gram of nickel formate was added and the solution was heated to 90°C for five minutes. Upon cooling, the solution wa transferred to a 125 ml. separatory funnel. A total of 50 ml. of methyl ethyl ketone was used to extract the fuchsin. Although the color of the dye was immediately evident, the intensity increased gradually over a period of a few 43 hours to a maximum and fairly constant value. Transmittance of the solution at a wavelength of 548 millimicrons was checked at one hour intervals. By referring the maximum value of Optical density received to the calibration curve in Figure 10, the concentration of fuchsin was obtained in milligrams per liter of methyl ethyl ketone. The amount of fuchsin recovered from the deposit was then computed by dividing this value by twenty. Recovery of Fuchsin From the Acid Solution The gradually increasing intensity of the color of the methyl ethyl ketone after extraction of the dye from the nickel chloride solution was similar to the effect observed while working with the reduced fuchsin solutions. As was previously mentioned, color development of the re- duced fuchsin solutions also occurred slowly. Moreover, recovery of the fuchsin was never complete. An analogous loss of fuchsin was thus eXpected during the dissolution of the nickel deposit; the stronger acid solution and the higher temperatures employed here, were not expected to aid the situation. To determine the efficiency of recovery of the fuchsin from the nickel deposit, numerous samples containing known amounts of the dye were treated at varying temperatures with, (1) dilute hydrochloric acid, (2) concentrated (36 percent 44 by weight) hydrochloric acid and, (3) concentrated hydrochloric acid and nickel. Initial eXperiments were conducted with twenty—five ml. samples containing 40 and 80 micrograms of fuchsin. They were acidified by the addition of three to five ml. of concentrated hydrochloric acid. After remaining for a period of time in acid solution, the fuchsin was regenerated by raising the pH value into the range of 4.5 to 5.5. Methyl ethyl ketone was used to extract the dye from the solution. To approximate more closely the conditions used in dissolving the nickel foils, 25 ml. samples containing 40 micrograms of fuchsin were carefully evaporated to moistness. The fuchsin residue was dissolved in 15 m1. of concentrated hydrochloric acid. Amounts of 1.2 grams of cut nickel foil that contained no fuchsin were added to a number of these solutions. The nickel foil had been prepared in a manner identical to the detached bright nickel deposits with the exception that Watts nickel solution was used as the electro- lyte. Some of the acid solutionswepelnwm;at room temperature; others were heated at elevated temperatures. The samples ‘that contained the cut nickel were allowed to react to completion at their reSpective temperatures. At the end of the prescribed time, the solutions were analyzed for fuchsin in accordance with the procedure described under "Dissolution in a non—oxidizing acid". 45 A complete evaluation of the effect of temperature, acid concentration, and reduction on the fuchsin was not possible due to the large number of tests that would have been necessary. Some idea of the influence of these factors on the destruction of fuchsin is presented in Tables I and II. The amount of fuchsin recovered from those solutions which were subjected to conditions that approximated the ones used in the dissolution of the bright nickel deposits was equal to about 60 to 65 percent of the original amount of fuchsin in the solution. It should be noted that the effect of the reduction and the acid on the fuchsin probably was much greater in these experiments since all of the dye was present in the solution at the beginning of each test. The opposite was true of course in the dissolution of the bright nickel de- posits; in those cases only a gradual amount of fuchsin was released into the solution. Accordingly, the percent of fuchsin recovered from the bright nickel deposits may have been higher than what was recorded in these determinations. 46 TABLE I RECOVERY OF FUCHSIN FROM HYDROCHLORIC ACID SOLUTIONS SUBJECTED TO DIFFERENT CONDITIONS OF TIME AND TEMPERATURE Amount Present Initially { } Fuchlin 36 Percent 1 Temperature Time Percent (’48-) ACid (°C) in Recovered (Ml.) (Hours) 80 3‘ 95 0.1 9“ no 5'l 95 0.1 87 no 3‘ 70—90 0.1 94 b0 33 70-90 ' 0.1 9# no 3a 70-90 0.5 77 40 3a 70-90 1.0 63 #0 3a 25 0.2 100 “0 5 25 0.2 100 40 15 90—95 4 58-5 40 15 90-95 h 58.5 #1 15 60-70 4 6h #1 15 60-70 h 65 42 15 50-55 1 64 42 15 50-55 2 66 “2 15 50-55 3 58 42 15 50-55 a 60 84 15 50-55 6 72 #0 5 25 24 86 40 10 25 2a an 40 15 25 24 8b #0 10 25 72 6O “0 15 25 168 57 3.Plus 25 ml. of water v—f iv TABLE II ERNEST OF REDUCTION WITH 1.? GRAMS OF NICKEL AND FIFTEEN ML. OF CONCENTRATED HYDROCHLORIC ACID ON 40 MICBOGRAMS OF FUCHSIN -..?va Conditions Used Percent Fuchsin v* v- Recovered Temperature Time (°C) (Hours) 80-85 1 72 80-85 4 #6 70-80 4 64 60-70 4 60 50-55 H 63 50-55 h 60 25 #8 58 25 168 58 25 168 66 CHAPTER III RESULTS Eflflggt Qfl Eughsin Concentratign 9n the Amount MW Bright nickel solutions measuring one liter and containing from #75 to 3,080 micrograms of fuchsin were used in the prepartion of ten nickel deposits, each of which weighed about 1.2 grams. The nickel deposit obtained from the solution that contained 475 micrograms of fuchsin was foggy around the edges; the other deposits showed ex- cellent brightness} Brittleness of the nickel deposits in- creased sharply at the upper concentrations of fuchsin. The data obtained from the depositions are shown in Table III. .The amount of fuchsin that was recovered per gram of nickel increased at the higher concentrations of the brightener. Although conditions and equipment were kept as much alike as possible in the different electrolyses, a comparison of similar initial fuchsin concentrations showed wide variation in the amount of the dye recovered from the deposit. That this variation could have been due to differences in Solution Analyses TABLE III EFFECT OF FUCHSIN CONCENTRATION SOLUTION ON THE AMOUNT OF BRIOHTENER RECCVERED FROM THE DEPOSITS 49 IN THE PLATING Fuchsin Recovered from the Deposits A4 b"I‘hese deposits were dissolved at room temperature decrease of fuchsin in the solution ”$571133?“ D8333 T6323 Pm???” ogefiéifi Decreasea gag.) 675 A05 130 16 12.3 12 950 770 350 45 12.8 29 1425 1215 415 69 12.5 52 2000 1875 275 63 23.2 55 2035 1780 510 92b 18.1 70 2050 1775 540 102b 18.9 78 2050 1930 250 76b 30.4 57 2875 2615 515 142 27.6 105 2925 2740 345 111 28.1 83 3080 2865 460 93 20.2 70 a-Defined as a 0 found 1 t e de osi x 100 M/C’ROG/PAMS FUCHS/N PER SPAM N/CKfL 50 C) lOO*—-—- .____‘ ,.._.__.._ x / / /rO 80—_—”— (J / '**“fi / / P~——— (3 /,/ ——+}ai / / 60L—— // O ...... / o s...“ /G _______J / / / h—_——. / ”...—q f) / 20-———— / —___4 / (’5 o 500 * 1500 2500 MlC‘A’OGA’AMS FUCHS/N PEP L/TE/i’ Figure 10. The amount of fuchsin found in the deposits as a function of the average brightener concentration in the plating solution. 51 solution agitation was indicated by corresponding relationships between the amount of fuchsin decrease in the solution and the amount recovered in the deposit. Where the latter value was large, the fuchsin decrease in the solution was also high. Amount gfi Fuchsia gggoxeneg from Consecutive Depositions in the_Same Solution In order to determine if the amount of fuchsin in the deposits changed appreciably as repeated depositions were made from the same solution, three types of eXperiments were conducted. The first of these was a pair of four consecutive depo- sitions from bright nickel solutions that were initially high in fuchsin concentration andto which no furthep additions of brightener were made. The solutions, which were used,con- tained an original amount of 2,875 and 2,925 micrograms of fuchsin. The results of these depositions are shown in Table IV. Although the initial fuchsin concentrations of the two solutions were almost alike, the amount of fuchsin found in the first deposit from one solution was much greater than that found in the corresponding deposit fromthe other solution. A similar parallel was noticed in the amount of decrease in brightener concentration of these plating baths. Further- more in the succeeding depositions if the amount of included 52 TABLE IV DATA OBTAINED IN CONSECUTIVE DEPOSITIONS FROM TWO BRIGHT NICKEL SOLUTIONS CONTAINING DECREASING AMOUNTS OF FUCHSIN Fuchsin Recovered from the Deposits Solution Analyses Initial Average Decrease Total Percent Per gram £ag./liter) Lag.) tag.) of of Nickel Decrease‘ gag.) 2875 2615 515 142b 27.6 105 2300 2065 435 106b 24.4 ‘ 88 1790 1685 215 7ob 33.3 52 1530 1445 170 40 23.5 30 2925 2745 395 111 28.1 83 2465 2310 310 102 33.0 80 2070 1940 285 91 32.0 69 1740 1605 280 84 30.0 65 a Defined as amount of fuchsin found in the deposit x 100 decrease of fuchsin in the solution. b These deposits were dissolved at room temperature- M/C/‘POGV‘PA/V/S 60675-75/71/ PER 6794/4 Mara. 100 Po 60 -~ 20 Figure 11. l i ——- ———+ _~—.—-_-.—._4 ...—.-.“... ._._ _ .-.-..- _._4 . 3000 M/CA’OGRAMS FUCHS/N PERL/727‘? The effect of average brightener 53 concentration on the amount of fuchsin recovered from two series of consecutive depositions. 5 4 fuchsin in one deposit was larger, then the decrease in fuchsin concentration of that solution was also greater. Such irregularities between the two solutions must again be explained by an inability to maintain uniform concentration at the cathode surface during deposition. The next experiments of this nature involved a series of four successive depositions from a liter of bright nickel solution in which the fuchsin concentration was readjusted to 2,000 micrograms per liter prior to each electrolysis. The data in regard to the amount of fuchsin recovered from the deposits at constant brightener concentration are presented in Table V. The magnitude of these values once more seemed to bear a relationship to the amount of decrease in the fuchsin concentration of the plating bath. The in- crease in total organic concentration did not appear to affect the amount of included fuchsin. The last in these series of consecutive depositions were made from a liter of bright nickel solution containing 2,000 micrOgrams of fuchsin to which had been added O.hb grams of zinc sulfate. The fuchsin content of the plating bath was readjusted to the initial concentration prior to each deposition; no further additions of zinc sulfate were made. The presence of another brightener of the second class, zinc sulfate, on the quantity of fuchsin found in the deposits is shown in Table VI. A much lower value was obtained for 55 TAB E V DATA OBTAINED IN CONSLCUTIVB DWPOSITIONS FROM A BRIGHT NICKEL SOLUTION ADJUSTED TO SIMILAR INITIAL FUCHSIN CONCENTRATIONS Solution Analyses Fuchsin Recovered from the Deposits Initial average Decrease Total Percent Per gram Sag/liter) (,yg.) Lag.) of of Nickel Decrease Lag.) 2035 1780 510 92 18 70 I950 I705 290 72 24.8 54 2005 1925 270 70 25.9 53 2005 1855 320 88 27.8 66 TABLE VI DATA OBTAINED IN CONSECUTIVE DEPOSITIONS FROM A BRIGHT NICKEL SOLUTION CONTAINING AN ORIGINAL AMOUNT OF 0.04 GRAN OF ZINC SULFATE. FUCHSIN CONCENTRATION ADJUSTED TO SIMILAR VALUES PRIOR TO EACH DEPOSITION Solution Analyses Fuchsin Recovered from the Deposits Initial Average Decrease Total Percent Per gram fias/liter) tug.) keg.) of of Nickel Decrease gag.) 2000 1800 360 62 17.2 36 2025 1730 295 79 26.8 #2 2000 1890 315 97 30.8 53 2075 1895 361 luO 38.8 78 56 the fuchsin content of the first deposit than what had been observed in the previous set of depositions. However in the succeeding depositions, the amount of fuchsin found in the deposits rose steadily to a value which compared favor- ably to that received from a bright nickel bath containing no zinc sulfate. I C D (D of c I ude t De 0 The effect of current density on the amount of included fuchsin was determined by means of a Hull Cell. The 250 ml. portions of bright nickel solution, which were used in the preparation of these deposits, each contained an initial amount of #70 micrograms of fuchsin. The weight of the deposited nickel was equal to 1.995 grams; the total decrease of the second class brightener in the solutions was 322 micrograms. The nickel deposits were excellent in appearance. Slight fogginess was observed inthe low current density area of only one of the deposits. All showed a trace of burning at the high current density edge. Such characteristics are usually obtained on a good Hull Cell deposit. Table VII shows the results obtained in the analyses of nickel deposits from five current density ranges. There is a notable increase in the amount of fuchsin per gram of 57 nickel that was recovered from the low current density area. An increase in the amount of included fuchsin at lower current densities was expected since a slower rate of deposition decreases the tendency for depletion of fuchsin molecules near the cathode surface. A fuchsin content of 62 micro- grams per gram of nickel was obtained from the deposits which had been plated at a current density of 15 - #0 amperes per square foot. This value is in close agreement with the results that were arrived at in the regular depositions made at a current density of 24 amperes per square foot. TABLE VII DISTRIBUTION OF FUCHSIN IN HULL CELL DEPOSITS 58 g: Current Amount of Fuchsin Recovered Density2 Nickel Dissolved i (amps/ft. ) (grams) er Per Gram Deposit of Nickel 0-15 0.125 14 112 lS-HO 0.h05 26 62 80-120 0.33# 8 2h )A120 0.409 12 29 1.8u9a 90b ‘. The total nickel deposited was equal to 1.995 grams. ‘b.fPhil value was 28 percent of the total decrease of fuchsin in the plating solutions. CHAPTER IV CONCLUSIONS A large share of the decrease in the concentration of fuchsin during the process of bright plating can be at- tributed to the inclusion of the brightener in the nickel deposit. Fuchsin contents ranging from 12 to 39 percent of its decrease in concentration during deposition were recovered from the deposits. The amount of fuchsin actually included in the nickel undoubtedly was greater than the amount detected, since possibly as much as 30 to #0 percent of the brightener may have been destroyed during the dis- solution of the deposit. _ Despite the apparent loss of fuchsin during dissolution and also difficulties encountered in obtaining uniform solution agitation, the quantities of fuchsin recovered from the nickel deposits were found to be dependent upon the concentration of the brightener in the plating solutions. Higher fuchsin concentration generally led to larger amounts of the brightener in the deposit. According to a recent article by Leidheiser (22X fuchsin is very effective in increasing the cathode potential during deposition. 60 In this paper Leidheiser reported that: The compounds most effective in increasing the cathode potential during deposition both decrease the grain size and change the type of preferred orientation to a type other than (100) or to a random distribution of the crystals. He mentions further that: In reneral, ductile deposits are associated with a (100 preferred orientation and brittle deposits are associated with an orientation other than (100). The deposits prepared in this investigation exhibited in- creasing brittleness at higher fuchsin concentrations thus suggesting a reduction in grain size of the nickel or a change in the type of crystal orientation. Either or both of these effects could be related to the corresponding larger amounts of fuchsin that were recovered from the deposits. Since the percentage of fuchsin found in the nickel deposits was very low (about 0.01 percent), it is possible that during the mechanism of bright plating,the fuchsin mole- cules attach onto the cathode only at special points. The attachment could be at high current density points, such as grain corners and edges. Deposition of nickel would then be interrupted at these places and accentuated at low current density areas. Such action would smooth out the deposit and produce a bright plate. To lend support to this hypothesis a ratio of fuchsin molecules to nickel grains could therefore vary from 1.8 x 1017 to 1.8 x 1017 1.12:: 101“ 1.12 x 1017 or 1600 to 1.6 l 1 - 62 A grain size slightly smaller than 10-5 mm. would result in an equal number of fuchsin molecules and nickel grains. Reference to Table VIII shows that depending on the grain size produced it would be possible for the included fuchsin molecules to cover the edges of each grain or merely the corners. Attachment of the organic molecule along the grain edges and/or the corners during depositivn could restrict grain growth. A higher fuchsin concentration in the solution would then increase this effect by making a larger number of fuchsin molecules available at the nickel surface. Subse- quently, and as was shown to be true in this investigation, greater quantities of fuchsin will be included in the de- posit and could lead to a smaller grain size as is reported for brittle deposits. DISTRIBUTION OF 100 MICROGRAMS IN ONE GRAN 0F NICKEL TABLE VIII 0F FUSESIN 63 Grain Size Fuchsin Molecules Length of Grain (mm.) per Grain Edge per Fuchsin “DIESEEO 10‘“ 1600 1.9 5 10”5 200 7.5 u 10-5 100 12.0 3 10"5 43 21.0 2 10"5 13 u?.0 10"5 1.6 ---~ 9 10"6 1.2 —-~~ 8 10"6 0.8 ---- CHAPTER V SUMMARI The purpose of this investigation was to determine whether a brightener of the second class is included in nickel deposits during the process of bright plating. The effect of brightener concentration and current density on the amount included were also studied. Fuchsin, a member of the tri—phenyl methane family of dyes, was chosen as the second class brightener because it could be extracted from the nickel solution and detected spectrophotometrically in concentrations as low as 50 micro— grams per liter. Reduced fuchsin, which is used as a commercial bright- ener (11), was also employed in a number of experiments, but a suitable method could not be developed for its analysis. The unstable and erratic behavior eXperienced with the re- duced fuchsin solutions was suspected to be due partly to the presence of a free radical. Existence of the free radi— cal at the dropping mercury electrode was confirmed from the equation of the cathodic polarographic wave of fuchsin. Depositions were generally made from one liter amounts of bright nickel solution upon buffed and passivated nickel .65 cathodes. When the effect of current density was studied, the electrodeposits were prepared from a Hull Cell, which held 250 ml. of plating solution. In order to analyze for the included fuchsin, the detached nickel deposits were dissolved in concentrated (36 percent) hydrochloric acid. After the pH values of these solutions were raised to n.5, the dye was extracted with methyl ethyl ketone. Despite an apparent loss of fuchsin occuring during the dissolution procedure, sizable quantities of the dye were recovered from the deposits. Moreover, the following trends were observed to have taken place: 1. The amount of fuchsin found in a deposit increased with its concentration in the solution. 2. The presence of another brightener of the second class, zinc sulfate, in the plating solution seemed to de- crease the amount of fuchsin in the deposit. 3. As noticed from the Hull Cell depositions, an in- crease in current density brought about a decrease in the quantity of fuchsin recovered from the deposit. With a value of 0.01 percent as the amount of fuchsin included in a typical deposit, ratios of fuchsin atoms to nickel grains were calculated for various grain sizes. With a grain size slightly smaller than 10-5 mm., the number of nickel grains and fuchsin atoms in the deposit were found to 66 be equal. Thus it appeared that during the mechanism of bright plating these organic molecules may attach at special points on the cathode-~grain edges and/or corners of high current density. (1) (2) (3) (b) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) LIST 0? REFERENCES Pinner, W. L., Soderberg, G., and Wesley, W. A.fl Chapter 13. Nickel. Gray, A. 0., Editor, Modern Electroplating.“ New York: John Wiley and Sons, Inc., 1953. Pp. 311-17. Blum, W., and Hogaboom, G. B., "Principles of Electro— plating and Electroforming." 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