N I l i \|\ a); '—-I I0); 'CD-b—I €-;:2.: urn.w‘a'3;;n‘thmcr 51:6:‘1 .; P.:..&r¢3;-r‘€k~.i OF SOME WEAK ACIDS IN NON-AQUEOUS MEDEA ‘. : r5! kghwfiv u.;!'.1“".-‘.\p n'. Thesis 5%» fhe Degree of M. S. fliECHEGAN STATE *JNNERSE'FY Ray Haoser E956 ; «i . '.-‘ - U (7 w: o t ‘ ‘v . Uni-vengy ;' fivflwmnm C .. a A- 4!..4 .. L. a 1L 0 1 t I ‘11 1x. I RSI. wl-I‘lla -‘ II\\‘ ’ . ... f. .f HIGH FREQUENCY TITRATION OF SOME km ACIDS IN NON-AQUECIJS MEDIA By Ray Hooser A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry Michigan State University East Lansing, Michigan 195 6 ACKNWLEDCHENTS The enthor it greatly iniabted to Dr. Andrew Tinnick whole kindnes- nnd petient supervision node the completion of thin investigation possible. Grateful acknowledment in also due to Dr. K. G. 'Stone and Dr. W, 1‘. Lippincott for helpful enggeetione, end to Hr. D. 1. Column for his timely “listen“. HIM FREQUEXCI TURBIOI N SHE max ACIDS IN NCI~AQU EOUS MEDIA By Rey Hoocer AN ABSTRACT knitted in Mid fulfillnent of the requiremente for the degree or MASTER OF SCIENCE Department of Ghenietry Ieer 1956 ‘Ppmed 4W.— iii ABSTRACT A grid-dip, capeoitetive type high frequency titretion epperetue opereting et lhl ”peyolee we need to deter-me ehether high frequency titretione of week eoide in eprotio' or baeio eolvente ere practioel end whether the neth offere eny edvantagee over potentionetric or indiv- eeter nethode of enelyeie for these solvent eyetene. Sueoeeeful high frequency titretione of n-uinobeneoio, beneoie, nelenie, g-nitrobeneoio, end ealioylio wide were perfor-ed in beneene- lethenel lined eolvent ei'th‘poteeeiun nethoxide in beneene-nethenel. lo euooeeeful high frequency titretione of oeteohol, hydroquinone, phenol, or reeoroinol were eooonpliehed enploying thie eolvent-titrut ml. Reeeoetophenone , B-quinolinol , 2 ,h ,6—triohlorophenol, or nnillin were moeeefully titrated in dinothylfomaldde with poteeeiun nethezlde in heneene-nethanol. The end point breelce for benzoio eoid, salicylio eeid, er lethyl eelioylete ranged from poorly defined to indeterlinete. lo euoeeeefel high frequency titretione of phenol or outeehol were eoeomliehed employing this eolvent-titrent eyeten . High frequency titretione of very weak eoide in dinethylforlenide with dooholio poteeeim hydroxide titrent proved euooeeeful for the Ienohydroq phenole , B—beneylphenol , Bohronophenol , g-Mroxydiphenyl , 29mphthol, end phenol. The end point breeke for g-tert-emylplmnel were eherp but the reeulte are very erratic. High frequency titretion iv I - e e M . . q . . . I .- a F‘ n e 1 , . , . ' . ‘ ' .u . ; , . .. ~ ‘ ,9 - , - e - e e ‘ ' | . Z 4 ‘ v _ . . x . .‘ ’ I | . ‘ ' . .. . o v - - 4 f < ,' | e s . , - ‘, . A - 5 —- - e e of ceteohol or phloroglucinol were unneeeeeful, poeeibly beoeuee of exidetion in emcee beeio titrant. High frequency titretione of edipic eoid , ruinobeneoie , beneoio eeid, ethnic eoid, methyl eelioylete, g—nitrobeneodo eoid, B-quinolinol, "WW”, 2);,6-trlohlorophenol, or vanilla in dilethyflormemide were performed eucoeeefully with alcoholic: poteeeiun' hydroxide titrent. ' Although comparable titretion reeulte m obteined for the di- Iethylferlenide eolvent eyeten by high frequency end potentiuetrio sewage» high frequency nethed 1- lore ecu-«nu einee the electrodes do not eeee inte mm uith the anthem. titreted. By a... high frequency method very m eoide were eunuch: dinetlvlfornanide. Such titretione he" not been emied out euooeeefully by en indioeter lethal. l t TABLE CE" cmms Pep mmmeIOOOOCOOOOCC0.000...0.0.0.0...OOOOOIOOOOOODOOOOOIOOO Emma lmmeDOOOOCQOOOOOOCO00......IOIOCOOOOOOOOOOOICC... Hon-191100” witMtryeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee High Fflqmmy 'mqm Titrmtneeeeeeeeeeeeeeeeeeeeeeeee mmuCCOOOOOOOCOCOCOOCDOC...0.0.0.0....‘IOOUOOOOOOOOOOOOO. R“FWOQOCOOIOOOOOIIOOOOOOOOOOOOIODIOOOUIOOOOIO09.00.0000... Wt”....QCOOO-OOOOOIOOOOOO0.0.0....OOOOOOOOIOOQOOOO0...... Titration mama...OOOOCIOOQOOCOOOO0.00000IOOOOOOOCOOOO... vumIOOOOOCCI0......00......000.....QCCCCCOOOOOOQOCOICOCCC PotantimtflcoOOO.00....0...OOIOOCOOOOOOOOOOOO0.0.0.000... commtmtncl...:COO0.000000CCOO-OOCOOOOOOOOOIOOOI.DIG... High anmy.00.000.00.000...O'COQOOOIOOOOOOIOOOOO0...... melou a WHSOOOOCOOOOIOOOOOOOQOOIOOOOOCOOIOOQOOOQCOOOOOO W GW.OOIOOCOOOOOOOOO0.00.0... OCOIOOOOOOOOOOIOOOOOI. Titretione in Demon-Methanol Solvent (Potueiun Motheride u Titr‘nt 0.00.....OOOOOIOOOOOOOCOOOOOOOOOOOOOOQOOO0.00...... High heqmmy...i...I.O000....COCOOQCOOCOOO‘C'OOCCCOCOOCOOOC Titratione in Dinetlvlfornenide Solvent (Poteeeiue Methoxide “ Titmt 00......OOOOOIOOOOOOOQ‘OOOOOOOOOOIOOCOOQOOOI0.... omdue‘mtfloOOOOOOOOOIOOOO0.00.00.00.00000000COOOOOOIO... PauntimtfloOOOOI.0.0.0.0....OQOOCOOOOOOOOIIOO.OOVOOCCOOO mgh qummy...OOCCCOCCCUOCOOCOCOCI .COOOCCOOOCDOCOCOCOCO Titretione in Dinethylforlmide Solvent (Alcoholic Poteeeiml Wfldo ” Tim)0......OOOOOOOOOOO.COCOOOOOOICCOOOOOOO Pountim00000.0000000000......CC.OIOOOOOOOOCOOOOOQOOOO men FNWBWOOOOOOOOO00......000000 O‘COOOOOOOOOOCOOOOOOO Titretione in Dimtmrlformmide Solvent Sodilnu Hothoadde u Titr‘nt)OOOOCOOOOOOO‘OOOOOOOOOCOD...QIOOOOOOOOOOOUOOOOOO... V1MCOIOOOOOOO.OOOOOOI00......I..(OOIOOOOOOODOOOOOOOOOOOI Ititratione in Ethylenedianine Solvent Sodium Hethoxide ee Titr‘nt DOOOOOOQIDOIOODO0.0COOOOOOOOOOOOOOOOCOOOOOOOCIOOOOO VMOOOOOIOOOCDOOOOOIOOOOOOOOOOOOOOOOOOCOOOQOOOOOO0...... Tmtion or Titration RomuOOOOI‘OOOOOOOOOOOO0.0.0.0000... 'Uneetiefeotory Solvent System for High Frequency Titrimetry.. m “D cmmmOIOOOOOOOOOOOCOOOO0......OOOIOOOOOOOOOOIOOOOO mm: OHEOOOOCOOIOOIUOOOOOOOOOOOIOOOCOOOOCOCOOOOOOOOOOOOOO vi p PEUSSfia co mo M p O~ LIST OF TABLES rm Page I Titratione of Very heck icicle eeepqeeeeeeeeeeeeeeeeeeeeeeee 38 II Titratione of Week Acids OOOOOCOCICOOOOOOOOOO0......0...... ‘41 vii LIST w FIGURES FICKIRE Page 1. Reepome Curvee for Potaeeim Methcdde, et Varioue ’flqmi°.eeeeeeeeoeeoeeeeeeeeeeeeeéeeeeeeeeeeeeeeeeeeeeeee 18 20 mm. cm.eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee 19 3. Reeponee Curve for Alcoholic Poteeeim Hydroxide............ 20 1;. High Frequency Titretion Curvee for Week Acide in Bemene- Hethenol, Potassium Hethoxide Titrent....................... 21 5. High Frequency Titration Curves for Week Acide in Benzene- ”W, ijou Kama.Titrmtee‘eeeeeeeeeeeeeeeeeeeee 22 6. High Frequency end Conductintric Titretion Curvee for Domain “idOCOOOOOCOOOOOCUOOOOOOOOO...00......000.000.00.00 21‘ 7. High Frequency Titration Curves for Week lcide in Dinethyl- fornenide, Poteeeiun Hethoxide Titrent...................... 25 8. CMI n.0‘m PufOWQOOOOCIOOOO.‘IOOOOOOQOOOOO...O... 2? 9 . Potenticnetric Titration Curvee for Vericue Phenole in Dilethylfornenide Titretcd with Alcoholic Potceeiun I.mz'O‘Id.eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee 28 lo. High Frequency fitreticn‘ Curvee for Very Week icide in Dinetkqlfornnnide , Alcoholic Poteeeiun Hydroxide Titrent. . . . 30 11. High Frequency Titration Curvee for Very Weak Acids in Dinethylfornenide, Alcoholic Poteeeiun Hydroxide Iitrent.... 31 12. High Frequency titration Curves for Week Acide in Dieethyle fornuide, Alcoholic Poteeeiun Hydroxide Titrant............ 32 13. High Frequency Titreticn Curvee for Week Acide in Dimethyl- , fer-elude, Alcoholic Potaeeiun Hydronde Titrant............ 33 in. High Frequency Titration Curvee for Week icide in Dimothyl- fornmide , Alcoholic Poteeeiun Hydroxide Titrant............ 3h 15. High Frequency Titration Curve for e Hitture of Phenol end 2A’6-Tr1cmmphan01000000.00.00...OOOOOOOOO...0.0.0.000... 36 viii a ‘ o o a a- e c v e 1 c 0 e 9 e O I a n u e u e . Q'I INTRODUCTION High frequency titretione ere purported to offer two dietinct edventegee over potentiometric titration: in non-equecue eyetenet l) the electrode ere not in contect with the eolution, thereby clini- ueting the eerioue problem of electrode deactivation and liquid- junction irreguhritiee end , 2) measurenente. necrothe equivelence point have no epoch]. eignificence. The end point ie doternined by the interaction of the extrapoleted straight line portione of the titration curve on either eide of the end point where the enceee of the ion being titrated er the emcee of the titrent will repreee the hydrolyeie, eclubility, or dieeocietion of the reaction produote. i nejor footer for the limited acceptance of high frequency titretien nethode bee heen the he]: of e eteble, eeneitive , reletieely eilple inetrunent cepeble of operating in the negaoycle region. Within the loot you, nowdcll, g_t_ g... (h) and Johneon and Tinnick (23).heve reported the developlent of einple , eteble inetrunente which poeeeee the deeired eeneitivity for both equeoue end non-aqueoue titrinetry. Llpplncott end emick (26) heve found thet the inetrlenent developed by Johnecn end finnick gen excellent reeulte for the titration of not, eebetituted enilinee in glacial ecetic acid eolvent with perchloric eoid in gleciel eeetic ecid. Therefore , this investigation wee under- telcen to deter-inc: 1) if high frequency titretione of week ecide in tprctio or beeic eolvente ere precticel end, 2) 1: the method offere cw edventegee over potentiometric or vieuel methods for theee eolvent eyetene. HISTORICAL BEKCRQIND Ion—aqueoue Titrimetr; Folio end Wentwrth (5) in 1910 carried out the am enelytioel non-eqnewe titretione with the titration of eome higher fatty ecide in nriouo eprotio eolvente with sodium elooholete, neing phenol- phthelein es the iniioetor . Although lone work all done efter this, the field lenguiehed until hrfuted, Lory, end Lode fornuleted their eoid-beee theoriee, thee putting mn-equeoue titrieetry on a more firm theorioel belie. The next senor edmoeuent we the etudy of 'euper wide" by Iell, Genent end Werner (1,16,17) in which they reported titretione of ink been in gleoiel eoetio acid medium eith etrong mineral eoide. The firet non-eqneoue eoid—beee titretion to find wide eooeptenoe he the procedure of ledeen end Brenchen (28) for the deteminetion of nine aide in mtio eoid with perchlorio ecid in ghoul eoetio eeid. loee, Elliott, end Hell (27) reported the euooeeefnl titretion of phenol end other very weak eoide in ethylenodianine with eodime mino- ethozide in the Isle eolvent . Ion-queue titrinetry came into proninenoe with the recent, repid expenlion of the ohenioel end phereeoentioel induetriee. Nunemne, repid oontrol prooeduree for my organic interlediete and fine]. prodnote Ihioh ere too week on eoide and beeoe to be determined in eqneone sedit- hed to be developed. 1 major ehere of the oredit for developing tbie field mt be given to Fritz (6-15). Riddiok (31.,35), Wollieh end Pifer (30.31.32) . All four types of eolvents, basic, ecidic, mphiprotic, eni We, here been utilized in non-equeous titrinetry (3h,3$). 1'). properties of the compound to be titrated must be considered in the choice of e suitable solvent. Since a basic solvent will enhance the apparent ecidity of week acids dissolved in it, ethylonodienine wuld be e proper choice of. solvent for titratione of ccmpomde such es phenol, ochroncxphenol, or cetechol. Likewise, en acidic solvent such es gleciel acetic ecid which enhances the apparent besicity of any seek beee dissolved in it would be chosen for eniline, g—chloroenfline, end pyridine. Since there is little or no lmling effect in eprotio end emphiprotic solvents, they are often selected when differential titretions of mixtures oonteining coupounde of eubstentielly different pK'e ere desired. in emplo of this would he the differential ti- tration of e mixture of phenol, eoetic acid, and hydrochloric ecid dileolvod in dinethylfornmide with elcoholic potassium hydroxide titrent (2). Among the many titrente suggested for use in non-equecul titrimetry, perchloric ecid in glacial ecetic acid hes been elnoet universally edopted for titration of week beeee . However, no one titrant hes yet been found uhichsetiefiee ell the requirements for e good titrent for week acids. Deel end Wyld'e suggestion of potassium hydroxide dis- solved in isopropyl elcohol eppears to the best developed thus fer (2). Other titrente which have been tried are potaseitm nethoxide, sodium nethcxide, sodium mimethoxide , end tetrebutylemnoniun hydroxide (5 ) . workers. in non-equeoue titrinetry have been plagued tron the beginning dth e leak of suiteble means of end point detection. 1-H Sane specific «indicetore ere eveileble, but no series of indicetors to cover the entire eo-celled "pH range“ for each solvent system hes yet been developed (6). Instrumental eethods of enelysis which have been utilised to circulwent this difficulty ere potantiometry (6) , photometry (33), conductimetry (18,19), and high frequency titrinetry (3,20,21,25,26,37) . or these, potenticnetric titrinetry has received the lost ettention. as problem ehich hes not yet been ccnpletely solved is thet of develop- ing an electrode pd: shich will give stable responee eai not be easily deactivated in non-equeous nedie. Of the any conbinetions suggested (6,2). the glusocelonel (sleeve type) electrode pair has given the best results of the peirs tried in this investigeticn. The preceding discussion is only s brief sketch of the developments in non-aqueous titrinetry. For s more complete treeteent, Riddick'e review (315,35) , Frite's booklet (6), end Pelit's monograph (29) ere excellent sources for interaction on this topic. Ligh Frequency Ion-queens Titrinetg Jensen and Perl-colt (21) who developed the first practical high frequency titretion epperetus in this country were else the first to recogniutb potentiel usefulness of high frequency titriletry for non-equeous systems ." II‘hey reported in their originel pepsr the success- m1 titretion of hensoic ecid or 2-phthelio eoid dissolved in eoetone dth eodiu lethoxide titrent . ""H For the next few years the literature on high frequency oscillat- ors was may devoted to improving instrumentation. Janhousld (20) has an excellent review covering this period. The first successful high frequency titratione in glacial acetic acid with perchloric acid dissolved in glacial acetic acid were reported by Wagner and Kaufman (37) . They compared potentiometric and high frequency results for aniline, p-teluidine, pyridine, and Ly-bis (2-cyanoetml)-2,s-dimthylpiporuine and expressed the view that results obtained fron high frequency titrations for these bases compared very fevombly with those obtained from potentiometric titrations. Unsuccessful titrations were reported for urea, ponitroaniline , and g-nitroaniline. ’ Jankovski (20) titrated successfully B—quinolinol, aniline, hexa- sethylenedialine . pyridine , diethylsniline , and 23de in glacial acetic acid with perchloric acid dissolved in glacial acetic acid. lie satisfactery‘end point for urea was obtained. Dean and Gain (3), using a Sargent 'Oscillcmeter,' reported good results for the. titration of salicylic acid, potassium acid phthalate , bensoic scid , g-nitrcphencl, boric acid, and smonilm ion. The samples were dissolved in dinethylfernmside and titrated with sodium methoxide in benzene-uthsnol. . The end point for phenol was unsatisfactory. Lippincott "and Timick (26) titrated a series of week, substituted snilines in glacial acetic acid with perchloric acid dissolved in the sane solvent, reporting results which compared very favorably with data obtained by pctentiometric and classical conductinetric titrations. rHi Ill It |.F Ii 5 d. ‘Irl. a» The compounds successfully titrated were I Aniline p-bronoeniline g-nitroaniline penicillin p—aminoacetophenone p—nitrosnilino p-toluidine raincbensoic acid poohlcroeniline goutmenilim They also ‘3‘! able to carry out differentisl titrstions , not possible by potentialetrio or conductisstrie nethods, of some pairs of the sub- stituted snilines listed. above . Lane (25), in order to evaluate the usefulness for non-aqueous titrilsetry of a portable instrument designed by Daedall, g _a_l_._.(h), titratedse-euskbssesinglscialscetisseidendsenemkacids in ethylenediesine. the cemennds were: In Glacial Acetic laid“ Imidins ‘ Deceme thylenebispyridiniun nitrate Wronquineline o-Phenanthroline adrenaline Phenasine itreaniline’ dine Homethylssetetrenine 2(2-Hydrcxypherwl) obensiminasole Dianisyldile thylphosphoniull iodide Dianisylethylnethylphosphoniun iodide Dishisyllsthylphosphine Tetraethylslncniun bromide tetrsethylauoniun iodide Tetreethylasncnilm nitrate Tetralethylsmncnilnn iodide Ethyltrinethylsmoniun iodide Phenyltrimethylslmoniun iodide Home thylenebispyridiniun nitrate Tri (g-hydrosyphenyl) ~sulphoniun chloride 'i'he quaternary moniun halides were determined by the mercuric acetate rougent nethod suggested by Pifer and wollish (31) . In Et glenedismine Dine dons 5-H itrophencl -Hydroxyquinolino 2 ( 2-Bydrcxypheny1) -bens oxasole h-Hydron-l, 2 ,3-bensselenadiasole 2,3-Dihydrexy-S-nethcmuinoxaline S-Hydroxy-Z ,3-diphenquuinonline . Srfiydroq-Q ,J-di (2-pm-1dy1) quinonline S ,8-Dihydrcxy-2 ,3-tetrsmethylenoquincnlins S ,Bquhydroxyoz uphenquuinenline S ,B-Dihydrclqv-2 -isoprcpquuinoxfl.ine 5 ,8-D ihydrqu-2 ,J-pe ntanethylenequinesalins Tri (rhydrozyphenyl) ~phospine oxide Iehidate and Hasui (38) titrated a series of nonobasie and dibasic carbonlic acids in benseno-nethanol nixed solvent nith sodium nethexide in beneene-nethanol. They reported the titration of a series of alkaloids and acid“ salts of sons organic weak bases dissolved in water or eater-alcohol with perehlorie acid in glacial acetic acid (39). In another paper (to) the titration of amino acids and organic bases dissolved in hormone-methanol eolvent containing some acetic acid with perchloric acid in" glacial acetic acid was reported. 1“H ' - - I .v a. v ‘ l e - I .- . . | e I a...“ i . 1 ’ ' ‘ s _- |' s. r ' Q 'Q SLJ . I . A ‘ ‘ i K . . - . , - a . v \ r I 1 e . e - s I y s ‘ v- < Reagnts No attempt to repurify the organic acids used in this investi- gation (except where noted below) was nude since most vere nominally 'pure." 1 cosxparison for a given compound of results obtained by potentiometric , high frequency, and visual methods 13s deemed sufficient basis for Judging the fluorite of high frequency titrinetry for ssak acids. To check the purity of phenol by an independent nethod, the brcnination procedure described by Siggia (36) as employed. Although Biggie. states that resorcinol can be determined in the seas Inner, satisfactory results sore unattainable. The compounds titrated, source and labeled purity, are: Weak icids' idipic acid obsueie acid nzoic acid Halcnic acid Methyl salicylate rNitrobensoic acid B-Quinoliool Resacetcphenone Salicylic acid 2 ,h ,6-Trichlnr0phsncl Vanillin Veg Weak Acids" p-Bensylphenol Sstechelhmol Recrystallised from acetic acid Eastman White Label Primary reagent grade (General Chemical Dow Camus 0m) Eastman White Label Eastman white Label Eastnan White Ltbfll Estman Yincite Label or. (Coleman 5 Bell) Unknown 0.3.9. (Retort Phanaceutical Co.) Eastman White Label Elm White Label Recrystallised from toluene ‘Thh classification will be used throughout the thesis to designate “compounds sinilsr to bensoic acid in their p]! values. This classification will be used throughout the thesis to designate compounds sisilar to phenol in their pK values. TH! Hydro quinone Eastman White Label 2-Hydroxydiphenvl Eastman White Label -Ne.phthol Matheeon Company henol Eastman White Label Phloroglucinol Eastman White Label Resorcinol Eastman White Label p—l‘ert-anylphenol Eastman Yellow Label Other chemicals used were: m Standards: bemoio acid, potassium acid phthalats, National Bureau of Standards or winery reagent grade. Other Che-inlet potassium natal, sodiul natal, antiw natal, lithiun chloride, potassiu- bro-ate, potassim bro-ids, potassiu iodate, potassiul iodide, and sodiu thioselfate , cheniedly pure. Solvents: ' butylaaine, Bastian White Label; ethylenediuias, Eustace, 95-40013 isopropyl alcohol, ethanol, methanol, and bemene,~oheeically pure grade; diaethyltorsanids, Hathesen's technical grads . Technical grade dinethylfornanide required a blank correction of approxilately 0.01; mini-equivalent per 150 milliliters . Dinethyl- tcrlsanide distilled at atmospheric pressure through a six foot long glass column packed with glass helices was found to have a larger blank correction than the charge (0.05 milk-equivalent per 150 milliliters solvent after distillation). Thus the dilethylforlanide used in this investigation was used as purchased. The blank was determined by con- paring the mount of titrant consumed with the theoretical alount of titrsnt required for a know: weight of bensoic acid. Direct potentio- eetric deternination of the blank was found to be unreliable. To prevent additional absorption of atmospheric carbon dioxide by the slightly . t \ 2 1 \ O a..- 10 basic dinethylfornanide,-the solvent was stored in glass bottles and transferred to the titration cell by'neans of a 50 milliliter auto-atic burst provided with guard tubes filled with ascarite'. “on med' nitrogen was used to force the solvent from the reservoir into the burst. The atopcock:of the buret_uas not greased since any grease extracted by the dimethylforeanide obscured high frequency and points. Alcoholic pom-aim hydroxiio“ (0.11: one 0.2611) use prepared by dissolving, with gentle heating, sufficient potassius hydroxide in too liters of isopropyl alcohol. After allowing the solution to stand for twelve hours, it ens filtered through a coarse sintered glass filter to remove the insoluble potassium carbonate. A nitrogen atlosphere was provided during the filtering operation to exclude atlosphsric carbon dioxide. The filtered alcoholic potassium hydroxide sas stored in glass bottles and dispensed from calibrated autosatic'burets. The burete were provided edth guard tubes filled.udth escarite. 'Oil pumped' nitrogen use used to force the titrant free the reservoir into the berets. These precautions vere taken to protect the titrant fro. at-ospheric carbon dioxide. The alcoholic potassium hydroxide was standardized against potassium acid phthalate dissolved in carbon dioxide-free dis- tilled water, using phenolphthalein.ae the indicator. .A.feu'of the standardisation titrations were carried out by high frequency titrinetry. One tenth normal potassium nethoxide and 0.18 sodiul‘aethoxide were prepared and standardised against benzoic acid as described‘by Frits (6). *rm to; alcoholic potassiun hydroxide is used in this thesis to designate potassius hydroxide dissolved in isopropyl alcohol. The non-aqueous indicators, thynol blue , ass violet, and 3-nitro- aniline, sore prepared as suggested in Prue's-booklet (6). Potassiu- beusats reunited for obtaining a high frequency re- sponse curve for potassiu heneoate in dinethylfcreaeide as prepared by adding potassius hydronds dissolved in otl'sanel to an alcoholic solution of bensoic acid. The resulting precipitate as isolated by ,filtrstion, recrystallised from hot alcohol, and collected by filtra- tion. The precipitate use then dried in a tacuus desiccator for 148 hours . Apaatue i Fisher 'Titrisetsr' vas used for all potentiometrie titration. Various oc-binations of the electrodes listed below were used: 1) autism, 2) Doom #1196 class, 3) seem #1170 fiber type sale-cl, and h) ink-an #167041 sleeve type calesel. ~ 1 lssfase ledel ace 1!» Conductivity Bridge, in conjunction sith a platinissd platinus i-srsion electrode pair («11 constant at 0.1), see used for the. cenduotieetrio titration. The capacitative type high frequency instrunent used in this investigation see a duplicate of the prototype designed and built by Johnson (22). The progress of a titration as followed by measuring the oscillator tubs grid current changes dth a Hodel m Sargent Polaromh. By the use of various combinations of capacitative type cells and coils or coaxial half-save line the operating frequency of the instrument could be altered. Tee capacitative type cells were e.ve 12 constructed. One was a band type in which two one-half inch side copperheads, scented one above the other approximately one-half inch apart, encircled the titration vessel. The other consisted of tee brass plates, one-half inch wide by one inch long, nounted against the titration cell at the sale level, but three quarters of an inch apart. Other constructional details are identical with those presented by Johnson (22). Operating frequencies were nessured nith a Signal Corps let. limiter-3042554 frequency ester. Thefreeuencis‘s fervarieuseeebinstieneefesnsaedeeileer half-save 11‘ '1'. I ‘. Cell Inductance tremor; Band type h2 turn coil 11 In Bead type 8 turn coil 36 MC Plats type b2 turn coil 15 no Plats type 8 turn coil h9 no - Plats up. Half-rm" line (as an.) no no The auto-atio bursts were calibrated using the titrant to be dis- pensed free then as the calibrating liquid. The coefficients of cubical expansion of the titrants were domd in a 25 milliliter dilate-ster at five degree intervals free 20 to 35°C. The coefficient of cubical expansion for 0.1! potassius nethoxids in benzene-Isthanol (lO/l) was found to be 0.12% per degree centigrade; for 0.1! alcoholic potassiu hydroxide, 0.111 per degree csntigrade. will release of titrant recorded in this investigation were corrected to 20°C. 1mquenoies were measured with the titration vessel filled with 150 sillilitsrs of diaethylforssnids. 13 ill analytical eeighiue sore weighed to the nearest 0.1 nilliuan, enploying weights calibrated against nation). Bureau sf standards calibrated Heights, Ltd. Tssthc. 87925. Titration Procedures 33221.. The compounds listed on page 8 as weak acids vere dissolved in so nilliliters of dinethylfornanids and titrated eith 0.1: sodiu- nsthozids to the first blue color of sec violet indicator (6). Before adding the eanpls the acid inpnrities in the dinethylfcrsanide were neutraliscd uith titrant to the sane blue color. The compounds listed on pages 8 and 9 an very weak acids ears titrated in 50 milliliters of ethylenedianins to the orange-red color of rem-uninh- with 0.1: sodiun nethoxide (6). u in ths case of dinethylferesnide the acid inpuritiss were neutralised before the addition of the sanplefi Pmticnetrie three electrode ccnbinations were used in this inveetigationc l) anthem-glass syste- for titrations of henscic acid dieeclved in dinetlvlfornanids with potassiun nethoxide, 2) calonel‘. (fiber)-¢lass systel for titrations of weak acids dissolved in dimethylfornanide with alcoholic potassim hydroxide, and 3) calonel (shard-glass cysts. for titrations of very weak acids dissolved in dinstlwlfornanide with alcoholic potaseima hydroxide . - The Fisher "l'itrinster' was balanced at 0.5 volts. 1h The eanplss vere dissolved in 75 milliliters of. dinsthylfereanide. A nitrogen atmosphere. was provided to protect the titration solution from atnoepheric carbon dioxide. Increments of 0.25 eilliliter of titrant sore added at the beginning of the titration. Near the end point the increments were reduced to 0.1 nilliliter. Conductinstrio ' The Serfass Conductivity Bridge was operated at 60 cycles. External capacitance cespsnsation use not seploysd since it did not seen to inprevs instrueent balance. . The saeple of benseic acid use dissolved in 100 nillilitsrs of diuthyiten-ude. The nuance vessel use rovidsd sith a sever to exclude ethosphsrie carbon dioxide. m Preguenox The inetrunent was allowed to m up for a sinieu «two here in order to stabilise its response. The sample see uighed to the neareet 0.1 eilligrae and transferred to the polyethylem tit'ation vessel. Tide vessel was then placed in the cell assesbly and a polyethylene cover, containia opsums for a nitrogen gas inlet,' glass etirrsr, and beret tip, was slipped over the nouth ef the titration vessel. The ector driven glass stirrer h“ positiued so that'ths paddle blades ssrs below the bade or plates. oh- hmdred and fifty amine». sf selvent eas transferred to the titration vessel with a 50 milliliter actuatic burst. After the nitrogen flow had been adjusted to a noderate rate and the opening for the burst tip plugged with a shall cork, the solution as stirred 15 for approximately 15 ninutee to establish temperature equilibrimn in the solution. thus the solution was attaining temperature equilibriun, the 3argent Hodel III Polarogrsph see tmed on, the span voltage set at one volt, and the proper sensitivity (usually 0.100 nioroanpere per this.) selected. After the required uniting period the titrant burst was positioned with its tip below the surface of the solution in the titration vessel. Unless a cceplste titration curve was desired, the bridge cent-cl of the polarcgraph me not adjusted to bring the scale pointer to the lower end of the scale until approxinetely all but five nilliliters of the theoretical mount of titrant required had been added. This step I was taken because the initial formation of the salt of any of the coepcunds titrated so “loaded" the instrument that either an extrenely large compensation setting was required to bring the pointer onto the scale again or the instrunent went out of oscillation for the particular bridge control setting. Once the initial amount of titrant had been added and the final adjustments of the bridge control mode , the titrant was added in increments of 0.25 or 0.50 nilliliter. Recorder readings were taken 30 seconds after each addition of titrant. Timed readings were necessary because of recorder fluctuations. Usually, readings were lads over a span of 10 milliliters, five milliliters before and five nilliliters after the-end point. 16 DISCUSSION OF RESULTS Respgnse Curves Response curves are obtained by adding in known increments to pure solvent one of the substances removed, added or formed during an actual titration and recording the oscillator tube grid current changes produced. Semi-log paper is used to graph response against nolarity because the concentration ranges involved in determining response curves extend through several powers of ten. There is no logarithmic relationship between response and molarity. If response curves for the titrant, titrant diluent, the compound being titrated, and the salt formed during the titration were available for a given frequency, theoretical titration curves for a given solvent could possibly be constructed. Usually only the response curve for the addition of titrant to the solvent is obtained. The response curves vary from hell to '8' shape, depending on the frequency, solvent, and titrant selected. Figure 1 shove the effect ef’frequency'ohangee upon the shape of the response curves. The linear portions of the response curves indicate the optimum concentration level at ehich the response of the instrument is linear and large for changes in concentration. This information is used to select the proper unpl- size to obtain optimum linearity in the titration curve . i rather couplets survey'at 11.negacycles of the response curves for the various elements involved in the titration of bensoio acid in dilethylfonanide with potassium nethoxide was made because of the l7 poorly defined end points obtained for this compound. From curve 0 of Figure 2 it is apparent that the response change due to the dis- appearance of bemoic acid during the course of the titration is “all. The slopes of the potassium bensoate curve (curve A, Figure l) and of the potassium nethoxide curve (curve E, Figure l) are similar. Little or no change of slope of the titration curve can be expected when ‘ potassiul bensoate ceases to be formed and the first excess of potassiu nethoxide is added. Benzene, methanol, or a eixture of the tee caused no response change when added to dinethylfornanide. The response curve for alcoholic potassium hydroxide was detersined at lhl negacycles. (Figure 3). Titrations in Bem'eneiiethanol Solvent Woman Hethoside as W h no A ratio of one part benzene to one part methanol was found to be a satisfactory lined solvent for the titration of p-aninobensoic , bensoic , nalonic , g—nitrobensoic , or salicylic acids 14th potassium lethozide titrant. Smooth titration plots and distinct and point breaks are obtained for these weak acids, as shown in Figures 1: and 5. The titration results for these compounds are listed in Table II. lle end point breaks were obtained for the titrations of resorcinol, hydroquinone , catechcl, or phenol. The acidity of methanol precluded the successful titration of these compounds in this solvent system. Pare bensene see also tried as a solvent for phenol but the instrument she'd no response on adding titrant to this solvent, even when 0.2 grail of lithiun chloride was added to provide some instrument loading. 8 1 3.0233: «:02; 2.223. mod Imu>¢ao umzoimum ..._ maze: mu.:1_ mun— quoz 0.. _.o 6.0 50.0 ‘ .oood _ _ _ _ ..\\. nus—mo A0 a S 0.2:: Mm I O 1 0.2 m. 4 V >ozm30mmm e m ozonezm>hom o .l I. 3 e .3 1 fl! 0 I1 ”I..— . O - -- . w l. e 4 ill. nqw. e N .20 ON U W I . Irl 3 I. 3 e B I. r _ _eee _ ..| S 19 _0 .0 w>¢=0 umzoammm m m h... mum «~40: 500.0 .0000.0 .0 0.0 _ _ _ os— __ H>ozw30mmm “:20 nhzm>40m Zooo goo on 8 :1 mzoxlm eoooxl< .N wane—n. SHELBWILNBO ‘NOIlOB'IJBO BWVOS 20 102.044 10.... u>m=0 wmzoammm . .n muse...— ¢m._..._ mun. muao: 19 .0.0 .00.0 .000.0 _ h _ a 0.2 :1 H>ozm30mmu “:20 "kzm>...0m 200m ssaiamiua o ‘NOIiOB‘IJBO awos 21' 9245; use. Jozithz _ umzm~zmm z. .0584 x33 mo... 3530 20.53:: ..._.I .v maze: wmmE.:.3.2 , v n J _ a __ _ . _ fl _ s .._s_. . N v II .I l . 3 v G . . 3 III 4. Tu 0 v v “H.— 0 1—: ¢N.D I .l. 20¢ 0 I. O LII], II I. _ O o 4. N . v C _ e o o I 4: who. m . L3 e N o .. l. O I. F oz : . In 42 2.0. 0.04 o...;o_._¢=o >2 ow ll. lr-li 10v. .044 1.53 . whack; “:39 2. 4029.3 _ P _ _ _ . _ _ _ H..— Si'IOAI'I‘IIW x ., :9. .o..< It; 32E: ”:3 25.629: / 2.5.x; mo... mm>mao zoF26“. .. some hxzmzeaerxomexé 8 . :I_ , .. .2 and Jozmquermmi.8 . . . .__z 5.3 JozmzdomohonfiQKN 2. .9952: -_ l _ _._ _ _ _ J 29 Titration results for the very weak acids are listed in Table 1. mm... results fer the weak acids are listed in Table II. High Pregnancy Distinct end point breaks were obtained for titrations of phenol, rbenzylphenol , p—brc-ophonol , g—hydroxydiphenyl , or i-naphthol , all very weak acids. Figures 10 and 11 are representative of the type of titration curves obtained for these canpeunds. Titration results are listed in Table I. Para-tert—anylphenol failed to yield stoichimctric results even though the end point breaks were sharp and well defined as shown by me C in Figure 10.. Stoichionetric results were unattainable for catechol or phlcro- glucinol . Black discoloration of the solutions after titration indicated oxidation of the compounds in an excess of titrant. No attempt was made to titrate resorcinol or hydroquinone . A possible solution to this oxidation problm muld be to bubble nitrOgen through the solvent to remove any dissolved oxygen before adding the sample. The titration curves for benzoic or salicylic acids were un- _ satisfactory. it best, the scattering of individual points blade the selection of the end point difficult. Titration plots, Figures 12, 13.and 114, for adipic acid, B-quinoliml, pcanimbenzoic acid, methyl salicylate , malonic acid, resacetophenone , g-nitrobcnsoio acid, 2,1: ,6—trichlor0phsnol, or vanfllin ranged from fair to good. Titration results are listed in Table II. .._.Zmm> mo... mw>mbo zo_._.szmna 8 o e .I 1.20.6. 402w1m4>2ZMIEO>XO¢0>I$ 3 e o N. luggage . o J .n C C C 1 C C m . w I s . s s IL H... 4.235 _. o . < m - o\._ o o O 1. e - N6. ,0 _\e I3 0 . N o o _ o 2:. m ti 0 O _ II I. e e 0 III. W e e s 3 I. o o o o 20 ¢ 3 ud s e , -II S . _ s . b b _ _ — — 9an; 1370.2 .53 z. moan v.3; Em... mo“. mu>mao 20:45: mi .: maze... n .. 3333...: ., _ _ 1 _ _ _ 4w _ 42223 nozmxn 8 Tail . r .:2 no... noxhxnnzo a . .:2 .o... nozmznozommlna . . . I. .n.m.momz.» as. :1 1 .0 423.3... . O .3 6.0... . m 20¢ ll, SHBLSWILNBO ‘No nos-1330 awos 32 .Pdek... 10v..0...< ”.220 z. mo.o< v.m30 zo...m=o zo.»mso 20:45:“...1 é. maze... $2.333: . Azure . . _ _.. _ n 42 new. nozmxnomonxoifio em 6 x ,. . mzozmxnopugmmm a o .v I m.u...uwm~u. z......z<> .4. o .1 I»... as. :1 o o o 3 o o .0: II C C '51-.— o 1 e s 3 < e O l o o o H. . . \o e o J. O 42 m¢ NN: m 0 6N e\_ _ e O. O .l e s . O . .. .l o o o o . .nznmm. o Gonna m s e s so 0 20.? H. e s s W e .il 3 o i o 3 r o. ...s. _ . a r _ . _ o _ _ . . s 35 As might be expected from pK values, the end point breaks for adipic or salonic acids were very well defined. The titration plots for EganinObsnzoic or genitrobenzoic acids, which have pK's similar to adipic and nalonic acids, did not exhibit sharply defined end points. There was such scattering of individual points of the plots for these acids. The whole weak acid group, except for adipic and nalonic acids, showed this tendency for scattered individual points of the titration plot, but not to such a marked degree. Differential titrations of mixtures of phenol and 2,14,6-trichloro- phenol were attempted. The data mm the two titrations performed, although not conclusive, indicate the feasibility of the simultaneous titration of‘ teak acids of different pK values by high frequency titrinetry. The results are: final Run II w Tam widOCCOCOCOOOOCCOCCCIOOCOOCOO 100.6% 9602‘; 2,h,6-Trichlor0phenol............... 97.9 112.8 Pmn°1OOCCOOOOOCCCOQC0......OOOOOUO. 103.2 82.3 Figure 15 shows the titration curve for Run I. Titrations in Dimeth lfornamide Solvent (3333311: Hothoage as Titrant) Visual Only two weak acids did not give entirely satisfactory titrations With aso violet indicator. The end point for adipic acid was obscured by precipitation of its potassium salt. Fading of the end point was observed then nalonic acid was titrated. Titration results are listed in Table II. I I I I F __ e , . O . O s ’ . e "T . ' “ U 4 OM . . . I- O uI__L ' . .. z /0 F5 0 ' Z ”.48 ML _ C... e _ ‘3" ~ - . A ,/ . z. 2— - s - .n— O . /. In e ’ .I _ __ 5.53 ML __ LI. 0 ‘3 e B O m_e , THEOREE .4 , . A) TOTAL ACID II.42 ML 3 B)2,4,6 TRIOHLOROPHENOL ‘9 . e 5.65 ML *- SOLVENT30MF "‘ e TWRANTiALcoKOH . UH MO I.‘ L L If I I I _ ~’ 1.. MILLILH’ERS FIGURE l5. H.F. TITRATION FOR A MIXTURE OF PHENOL AND 2,4,6—TR10HLOROPHENOL. 37 Titrations in Eth lenedienine Solvent ' {Sodiu- Ethofide as Titan” 1.1-2.9. The color change fro: yellow to orange-red for g—nitrcaniline indicator used for titrations in ethylenedianine with sodiue nethoxide is not as distinct as the change to blue of ass violet in Iii-ethyl- fornaeide. Little difficulty use encountered in determining the end point. Titration results for the very weak acids are listed in Table I. Tabulation of Titration Results The compounds titrated in this investigation were divided into tee groups, weak acids and very real: acids. This division is based upon relative strengths. The tables of experinental results vere there- fore organised on this basis. The titration results obtained free high frequency, potentiometric , and visual procedures for individual eoepounde are grouped together under the none of the ccupound in order to facilitate chparison. The sin of the circles used in the titration plots is not pro- portional to error because of uncertainty as to the sagnitude of error introduced by fluctuations of the recorder. 1!ng I. 38 satin-Iain i ewe ea cc nag §§ an “mn.nu en sag an §§ F! r E L. .isessudaguou gnu an. 34. «SA... noes Baa «B .36 an.» 83. .51. «Baa «a .3... 3.: 2.3.0 .8 6.: £86 an .3... 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