ANALYTICAL CHEMISTRY
66
(78) Ibid., pp. 186-200; Chem. dnI7l., 29, 268-76 (1947). (79) Hovorka, V.,and Holzbecher, Z., Collection Czechosloi. ('hem. Communs.. 14.248-62 (1949). . . (80) Iranova, A. P., and Chugunoi-a. V. I., P.S.R.R. Patents 67,911, 67,912 (Feb. 28, 1949). (81) Jaboulay, B. E., Rev. mSt.. 47, 53-4 (1950). (82) Jean, Marcel, Anal. Chion. .Ictn, 3, 96-9 (1949). 183) Ibid.,pp. 100-7. . H E M 21, , 1145-6 (1949). (84) Kallman, Silve, A N . ~ LC (85) Kaufman, Samuel, Ihid., 21, 582-3 (1949). (86) Kayas, Georges, Compt. rend., 228, 1002-3 (1949). (87) Keller, I. M., Doklody A k n d . .l'auk S.S.S.R., 67, 117-20 (1949). (88) Khripach, S. AI., Zanodskoya Lab.. 13, 1008-9 (1947:. (89) Klyachko, Yu. A,, and Kondratjuk, X. P., Ibid., 13, 901-16 (1947). (90) Kodama, Kaeunobu, J . J c i p n . ('hem., 4, 10-20 (1960). (91) Kul'berg, L. 11..arid Ledrleva. .I. AI., Zhur. Anol. A-hz'ni,, 2, 131-4 (1947). 192) Kummins, C. A , . .INAL. Ckn:., 19, 376 (1947). 3) Kusnetsov, V. I.. Zarodsknya Lot,.. 14, 545--5 (19481. 4) Lambie, D. A., Analyst, 74, 405-10 (1949). 5) Lassieur, Arnold, Chini. ( i r i u l . , 31, 123-4 (1949). 96) Liang, S.-C., and Chang, K.-?;.. Science R. 7'f~cAr~nl. P h i t i n . 2, 32-3 (1949). (97) Lockemann, Georg, 2. onrrl. Chem., 129, 213-17 (1949). 9 R ) Lur'e, Yu. Yu., andFilippova, N. 4.. Zorodskoya Lab., 15,771-9 (1949). (99) Magdalena, V. A., Anales ossoc. q i h n . g f n r m . C r i r g u o y , 50, "i-8 (1948). i I O 0 ) hfagneli, Arne, Arkiu Ken$ 1, 273-6 (1949). i.101) Malov, S. I., Zaz.odsknya Lab., 15, 997-8 (1949). (102) Mayants, A. D., Ibid.,13, 920-3 (1947). (103) Medoks, G. V., and Markelova, S. N., Zhur. A n a l . K h i m . , 1, 319-21 (1946). (104) hlonnier, D., and Resso, Z., Hclv. Chim. Acta, 32, 1870-1 (1949). (105) Aforeno Martin, F., Anales fis. g quim. ( M a d r i d ) . 41, 291-7 (1945). 106) hforette, A., Ann. pharm. franc., 6, 529-34 (1948). .107) Naito, Takio, Kinoshita. Y . Y., and Hayashi, Junichi, J . Pharm. SOC.,J a p a n , 69, 361-3 (1949). (108) Seclakantam. K., Proc. I n d i a n Acad. Sci., 27A, 202-3 (1949). I,lOOj Oesper, R. E., and Klingenberg, J., ANAL.CHEM.,21. 1509-11 (1949). i 1 11)) Olea Gomez, J., and Gaspar Romero. J., Tech. met. (Barcelona), 4, 461-3 (1948). i l l 1 i Osborn, G. H., and Jewsbury, h., $rial. Chim. Acta, 3, 108-12 (1949). :112) Ospenson, J. N., Acta Cheni. Scand., 3, 630-8 (1949). jllX) Ostroumov, E. A., Z h u r . A n a l . K h i m . , 2, 111-17 (1947). (114) Peltier, Simonne, A n a l . C h i m . Acta. 2, 328-9 (1948). (11.5) Penchev, N. P., Annuaire univ. Sofia, Facirltd phys.-mat.. 43, Livre 2,209-22 (1946-47). ' 1 1 6 ) Peshkova, V. hl., Vedernikova. >I. I., and Gontaeva. S . I., Zhur. A d . K h i m . , 3, 366-72 (1948). i 117) Pieters, H. A. J., A n a l Chim,. Bcta, 2, 411-16 (1948). ,118) Pilipenko, A. T., Zhztr. A n a l . Khim., 4, 227-31 (1949). 11 19) Plotkin, N. Z., Usatenko. Yu. I., and Bulakhora, P. A . , Zavodskaya Lab., 15, 999-1000 (1949). :\20) Poluektov, N.S., and Sikonova, hl. P., Z h w . A n d . K h i m . , 3, 354-61 (1948). I 21 ) Porfir'ev, N. A.. L a v r o v a S. > I , , and Evdokimov. V. V., Ibid., 4, 114-16 (1949).
( 1 2 2 ) Putzrnann, C. S., Anales a s w c . qui'm. argentina, 37, 2h4-2
1949). (123) Reed, S: A., and Banks, C. T , I ' m - . Iowa S a d . Sci., 5 5 , 267-75 (1948). (124) Rochat. R. J., Plating, 36, 817 (1949). (125) Rodden, C. J., AKAL.CHEM.,21, 327-35 (1949). (126) Rothaug, G. Z., Anorg. Chem., 84, 165-89 (1914). (127) Ruinionte, F. G., Annles real. soc. espafi. fZs. y q~iim.,45B, 65 (1949). (128) Ryan, D. E., Can. d . Research, 27B, 938-42 (1949). (129) Ryan. D. E.. and Fainer. P., Ihid., 27B, 67-71 (1949). (130) Sa, -4.hl., Ea.. assoc. bioquim. argentina, 16, No. 64, 11-16 (1949). (131) Sarudi. Imre. Hungarica Acta Chim.. 1, 41-6 (1948). (132) Sarudi, Imre. 2. annl. Clrern., 129, 96-104 (1949). (133) Schafer, Harald, Ihid., 129, 332-9 (1949). (134) Schellinger, A. K.. Eng. M i n i n g J . , 151, S o . I , 74 -5 (1950). (135) Schwarte, H. 4.. and Guiler, G. >I,, .Im. Forotdrymon, 16, No. 3, 53 (1949). (1%) denienko. V.A., Z n d s k a y n Lab., 15. 1472 (1949). (137) Shome. S.C., Analyst, 75, 27-32 (1950). (138) Yhredov, V. P., Zhztr. A n n l . K h i m . , 3, 29&4 (1948). (139) Silverman. Louis, M e t n l Finishing, 47, KO. 5, 62-5 (1949). (140) Silverman, Louis. arid Lembersky, H. K., . ~ N A L . CHEM..21, 983-4 (1949). (141) Smythe. .J. A , Atirrlys1, 75, 24-7 (1950). (142) Spakowski. A. E., arid Freiser. Henry. As if.. C H m f . , 21, 986-9 (1949). (143) Syrokomskil, V. S.. arid Klimenko, S . G I Zmodskaya Lab., 13, 1035-8 (1947). (144) Tananaev, I. V., and Lel'chuk, Tu. L.. Zhur. A n a l . K h i m . , 2, 93-102 (1947). (145) Tananaev, I. V., and Lerina, >I, I.. Ihid., 1. 224-35 (1946). (146) Tananaev, T. V.,and Rliaetukaya, I. B., Zacodakaua Lab.. 12, 529-33 (1946). (147) Tarasevich, N. I., Zhur. Anal. K h i m . , 3, 253 -7 (1948). (148) Ihid., 4, 108-13 (1949). (149) ThBry, R., Chim.anal., 31, 199-200 (1949). (150) Tokarski, J., Bull. intern. acad. Polon. Sco.. Clmsse Sci. math. nut., Ser. A , 1947, 107-12 (1948). (151) Ubaldini, I., and Guerrieri. F., A n n . chim. npplicatn, 38, 695-701 (1948). (152) Vstrenko, Yu. I., and Datsenko, 0. V., Z ~ c o d s k n y aLab., 14, 1323-7 (1948). (153) Ibid., 15, 779-81 (1949). (154) Vecchi, Gastone, Bull. Bwle Polytech. Jossy. 3, 85R-61 (1948). (155) Venkataramaniah, M., and Rao, Bh. 5. V, 11.. Current Sci. ( I n d i a ) , 18, 248-9 (1949). (156) Vinogradov, A. V., and Dundur, E. I., Zhur. Anul. Khim., 4, 117-21 (1949). (157) Voter, R. C., and Banks, C. T'., ANAL.CHEM..21, 1320-3 (1949). (158) Waterkamp, Maria, Arch. Eisenhiittenw., 20, 5 -8 (1949). (159) Wendland, R. T., and Smith, C. H.. PTOC. 2Vorth Dakota S c a d . Sci., 2, 40-3 (1949). (160) Wendland, R. T.. Smith, C. H., and Muraca. Raffaele. J . A m . Cheni. SOC.,71, 1593-5 (1949). (161) IYillard, H. H., and Boldyreff, A. W.,Ibid., 52. 1888 (19.70). (162) Yoe. J. H.. Frontiers in Chem.. 7,49-68 (1949). (163) Zagorchev, Boris, Compt. rend. acod. bulgare sci., S r i . math. et nat., 2, 49-52 (1949). ~I
RECEIYI?D October 3 , 1950.
Volumetric Analytical Methods for Organic Compounds WALTER T. SUITH, J R . , S t n t e l'nitlersity of
BE folloving discussron is 1)asecl primarily un reports in the literature from Ortotier 1949 to September 1950, h u t also inriudes some earlie] forvign i i u terial not previously covered in t hrse reviea s. DETERSIIN 4TION OF ELEMENTS C
ARRON
In a method designed for automatic operation the sample is turned to carbon dioxide and water as usual, hut then the water is rlhporbed in anhydrous harium chloride, the carbon dioxide i n
AND ROBERT E. BUCKLES Iowa, IOIM City, Iowa
converted to carbon monoxide by passage over carbori a t 1120" ('., and the resultant carbon monoxide reacts with iodirie pentovide in a manner similar to that in some oxygen determinations. The water formed in the combustion is evaporated from the barium chloride and passed over carbon a t 1120' to form carbon monoxide, m hich is then determined by the technique used for the carbon monoxide formed from the carbon dioxide above ( I @ ) . I n a new semimicromodification of the carbon-hydrogen conibustion method liquid samples are burned in such a n-ay that the hulk of the sample is kq)t rrl:ttivelv cml and slo\~lyvaporized by
V O L U M E 23, NO. 1, J A N U A R Y 1 9 5 1 heat applied near the open eiid of the ampoule. Completeness of c+onibu&ionas \\ell as decreased combubtion and sweeping times is obtained by using a fast oxygen rate and consequently increased pressure. The method is reported to give an accuracy of 0.06% tor carbou and 0.08% for hydrogen. The average standard deviation for carbon was 0.08% and for hydrogen 0.04%. Solid Pamples are burned in a special compartment boat (83). I n a webcombustion procedure for carbon, the Van SlykeFolch conibustion solution (146) has been used in ail easilv as*mibled apparatus and the carbon dioxide formed is determined by a titiation procedure (5'9). A determination requires about 45 ininuteq and gives results which are accurate to 10.05 mg. of carI)on. Samples of 10 to 12 mg. of carbon are used. Halogens, nitrogrri, and sulfur do not interfere, but compounds that I elease hvdrogen cyanide on decomposition give low values. HA LOG ENS
Decomposition of the sample by the mrthod of l)L),the sample is decomposed hy combustion a t 1250' i n a platinum tube in the presence of oxygen and water vapor. The fluoi ine is converted to hydrogen fluoride and determined by titration with standard alkali. The method has the advantage that carbon may be determined siniultaneously by ahsol liing thr carbon dioxide formed in Ascaritr. Coiiipounds containing both fluorine and sulfur have beeii burned in hydrogen in a plastic apparatus which is resistant to hydrogen fluoride and sulfur trioxide (96). The vapors are collected in a series of dilute potassium hydroxide traps. The contents of the traps are combined, neutralized to phenolphthalein with hydrochloric acid, and treated with barium chloride to precipitate sulfates. This precipitation is carried out in the presence of boric acid to prevent the precipitation of fluoride. The Huoride is drterirlined by the method of Ruiss and Bezmenova (116). Fluorine in compounds n-ith a fluorine atom on a carbon adjawilt to a carbon bearing a hydrogen has been determined by adding a n excess of 0.005 .V sodium hydroxide to the sample and after 5 minutes titrating the esress alkali to determine the amount of a( id liberated (105). C'hloiine and bromine in organic compounds have been deterininetl by fusion with potassium in a sealed tube, followed by titration n i t h silver nitrate using dichlorofluorescein indicator ( 4 7 ) . In another method (65) the sample is digested with a vhroniic-sulfuric arid mixture and the evolved halogen is ahyor1w.l in alkaline hydrazine and determined by the titration proc:rdutr of Sendroy (186). The average deviation is about 0.5%: the niasinium deviation is 1.0%. When bromine and chlorinr are 1)oth present, the results are not quite so good as with the btandard gravimetric niethods. ('hlorine in compounds of high molecular n eight has been deterniincvl i n the following m:Lniirr (do'). Three grams of pure potasqiuni hydroxide are placed in a steel bomb and covered with 0.1 to 0.2 grain of the powdered sample, followed by 3 grams of sodium tetraborate and 0.75 gram of potassium nitrate. The mixture is heated l hour on a hot plate and then 1.5 hours in a muffle a t 400" to 600". After cooling, the mixture is diluted to 250 ml. and a 10-ml. aliquot is neutralized with 20y0 sulfuric acid and titrated with 0.01 N silver nitrate solution. IIydiogen chloride is evolved quantitatively from polyvinyl chloride nhen it is heated to dull redness. This is the basis of a nirthod of analysiq for rhlorinc in surh polymers (138). The
67 evolved hydrogen chloride is absorbed an argentonietric titration.
in
n ater and determined L))
NITROGEV
A Dumas combustion tube M ith a wideried oxidizing rhanitrcv has been developed for the determination of nitrogen in niiner:tl oil samples. This modificatioii of the tube seems to have no bad effects on the determinations, und more analyses are possible on one filling of the tube (78). The somewhat controversial nickrlnickel oxide tube filling (16) is used successfully (71, 75). Such tube packing has now been successfully used in a number of industrial laboratories in Sweden for some time. Unsatisfactory results seem to be caused h v metal impurities which redwe carbon dioside (72). The Kjeldahl method of iiitrogeu analysis has been applied to the analysis of nitro compounds (f37). The sample is heated rn ith 20 ml. of sulfuric acid, 1 gram of pyrogallic acid, 5 grams of niercuric sulfate and selenium catalyst (14). After 90 to 120 ininutee the mixture is diluted, and the mercury is precipitated with monosodium phosphate. The anal\ is finished as usual. A mort rapid method which involves a Kjrldahl treatment with the srleiiiuni catalyst only has also been described. Mineralizatioii requires o n l r 15 minutee. The valurs ohtained in this case aie better than those previously reported (100) with this catalyet in the Kjeldahl analysis of nitro compounds. 4 iecent study has been made of the kinetics of the catdysie o f srleniuni in the Kjeldahl digestion (124). The results indivare that during the initial fast reaction catalysis is brought about b y colloidal selenium. The slower reaction which follows is catalvzc~l by coagulated selenium. Tlir Iljeldahl method of annlysis has been found reliablr f o r determining the amount of cyanoethylation product obtained i t ) the re:tcation of acrylonitrile rn ith amino acids (85). The e\(;ew acrylonitrile is evaporated before the determinations are carried out. The results of the Kjeldahl determination on the pure cyano compounds are only slightlv lower than those obtained I)? the Dumas method. h Kjeldahl digestion using m:inganese dioxide has been b u g gested (106). lrjitrogen in amides has been determined by treatment at 70" for 20 minutes with a mixture of concentrated hydrochloric arid and conrentrated nitric acid. The liberated nitrogen is collertcd and the volume measured. The method is reported to be siniplr and rapid (111). OXYGEN
-
Berret and Poirier (17) have obtained good results in tht. tic termination of oxygen in a wide variety of compounds by using :, modification of the Unterzaucher method (142) in which thr w r Imn ctioside is absorbed and weighed PAOSPITORUS
Foi thv (htermination of total phosphorus in organic phcI~ph.atcs, t n o niethods for decomposing the sample have bwn studied (130). I n the first the sample is refluxed with concentrated hydrogen iodide. Aliphatic compounds are deconiposed by this method in a matter of minutes, but aromatics mal require more than a week of treatment. In the second method studied the sample is oxidized with a mixture of perchloric, suifuric, arid nitric acids catalyzed by sodium molybdate. T h ~ c oxidation is complete in 30 minutes for both aliphatic and arc+ matic phosphates and appears to be the better of the two method6 In either method the phosphate is determined by the molybdiphosphate-alkalimetric procedures using A.O.A.C.procedure (;I SULFUR
Worden and Snynmn (10'1) h a w ieported that sulfur in (Brganic compounds may be detRrniinrc1 IJY a method of Elving &rid Ligett for halogen (34).
ANALYTICAL CHEMISTRY
68
.I nii~thod for the determinatiori of sulf'ur in organic thiocy:iti:itcs, isothioureas, thiocarbaniates, thiols, and disulfides is I):ii.cd on splitting the compounds with :L st:mdard solution of
S:i~l'I)(OH)~ (81). I n general, a n alcoholic solution of the compiiuiitl is treated with a NanPb(OH), solution containing 0.5% k:~tI,and the mixture is allowed to stand 30 niiriutee. The lead ipt'ide and lead sulfide are filtered off 1iy suction and washed with slightly alkaljne water. The excess 1 ~ a diri the filtrate is dettmiined b v precipitating as lead sulfalc, dissolving the precipit:\tt, in innmonium acet.ate, and titrating xith standardized aninionium molybdate solution, using tannin as the indicator. 111 :L method for the determination of sulfur in plant and animal m:itcbrinl (26) a 0.5-gram sample is heated in a porcelain or quartz imtit in an rttmosphere of carbon dioxide a t 760" to 800" v i t h 2 to 3 gi'tinis of oxalic acid and 1 to 2 grams of metallic cdcium. By tliii. pi,ocedure the sulfur in the sample is converted t o hydrogen sulfitlrl. 11-hich is absorbed in a solution of c:tdniium and zinc :rwt:ttes. The heat,ing requires 10 miriutc- :iiid tlic rntirr dtltclrniiri:ition t n k i ~only 15 niinutrs. FUR'CTIONAL Gl{OL~f'S
by niixing an alcoholic solut,ion x i t h water. This acid nuinlier is not proposed to replace any of t,he existing constants determined on fatty acids but rather to complement them (118). A similar method has been used to determine acid values of samples of lac. It is necessary to use aqueous alcohol (2 volumes of alcohol to 1 of water) as a solvent and to have excess iodide ion present. Best results are obtained when standard iodine solution is added a t the end of tlie reaction and the excess is titrated with thiosulfate (67). A novc.1 stud1 of reaction rates involving :icid-basc titrat,ion has bc3cii dcscribed. The reaction studied was the base-ratalyzed ethyl acetate saponification. The output of the reaction flask was hrld :it ii constmt rate Jvhile acid cont,aining phenolphthalein was mixed wit,h it a t a variable rate. Concentrations calculated from t,he flow r:itcs led to reproducible rate constants which checked those ol)t:iined by other methods (180). .A fairly c:oniprehensive study of the titration of organic wids in non:iqueous solvents has recently been reported (60). Carbosd rnd groups in polyamides have been titrated with iuni hydroside in benzyl alcohol' at 155' to a phenolpht.h:tlvin c s n d point (121) :wcording to thc procedure of Waltz and Ta,vlor ( I , # ? ) .
ACETYL
ALCOHOLS
11 is ri~l)i)~,ted that the losses eiicou~it!~i~c~tI $5 Iiili. ImiliIig to remove sulfur dioxide and carbon monoside i:i t h t s (lctt~riiiinationof :i 9 p t v i : i l cooling :irotvl groups may tie avoided by suxp~~iidinp picw in the nrck of t,he flask (66).
In :Lpro(:durc- for the cstitnation of alcoholic liyclrosyl groups the s:implc is trc:tted with an excess of acetyl chloride. The excess acc,tyl chloride is hydrolyzed by the addition of water and the acidity gencutctl i n the rraction is titrated xvitli st:indard alkali (83).
AC:IDS
I'lii~ti~l~~iiitioliiiecarboxylic acid 113s I ) W I I (11.1 ( ~ ~ ~ i i i i l)y t i i ~r z l ti,:i~ tion fwin :tqurous solution with rther, folloiwd by titr;ition of an :il(~oholicsolution of the estract with 0.02 -1-;cidiuin r:irlionnt~~ snlut ion (36). Iklir-dt~oc*holic acid has been dt~tc~rniiiietl i n ;I ,similar iii:i,nnrr, c'scvl)t th:tt the extract,ion is donr with ti~ic~hlorocthane (36). T h foimiir acid which is formrd in the i x k ( I ; i t , coxit1:ition ol < k . ~ t i : i i hi : i ~lieen determined (62). Tlw ,wluticiii i, twntcd n-ith I)uI'(' ~~thylorie glycol to reducc tlic (txcei.s p(~riod:itc~.T l i ~forniic vnti 1Hiiiit a-itli 0.01 S acid is their titrated to the phenolplit1i:tl~~iti sotliinii liydroxide. It, is found thnt 1)l:tnks of 0.5 to 1.O% result ft,oni tliv glycol reaction with ~jri~iodate.T l i ~w w l t s o1)t:rinetl \ v i l l i 1ilii~t~oil)hthslcin are moi'c ( ~ i i ~ ~ i ~t1i:tn t e n tthosc ul)tuined \\-it11 tlic WUBI methyl r t d as intlic~itor(52, 61. B1, 104). . \ ( , i t 1 l)tutluct formation has Iiecti follo\vctl in kinctic 11i(~1i1-tlt~olyrisof both acetates and tliiol:wetatt+ l ~ titr:i.tinn y ~ith sotti tin1 livdroxide solution (119). The aniount of decarboxyl~tionof zotliuni trifluoroacctate to g i w Auoriiforrn and sodium cxrhunatc has h c n f o l l o w d in a kiiic.tic stutly hy titration of boric acid which is present in excess .( 3 ) . T i 1 :I study of the kinetics of the hydi~olysisof p-propi~lnct~one the, concentration of 0-hydroxypropionic acid could be followed 1)y tlirrct, titration with base. The lC-ni1. sample of the rraction mixture is d d e d t o 90 ml. of ice watcr and titrated iinmediat,ely to the hromothymol blue end point. ('are is taken t o kecp any loc:~1concrntration of base from accumulating (84). T l i ~iodnmetric acid numbpr is defined as the number of milliliters o f 0.1 S iodine solution equivalent tu I gram of the acid. It, is tltltt.rinined by allowing a sample of tlie acid to react with excess 0.1 S sodium thiosulfate and 3% pot:wsium iodate. solution nrc o d i n g to the following equation:
Excess thiosulfate is titrated with 0.1 S totiine solution. Thc, clcteixnination ran be applied to e m u l ~ i o rof i ~ fxtty acid. made up
ibed a mct,hod using :iwtic anli>-drid(~and Auol)oric*:iritl in dioxane (146). T o 0.00L5equivalent of sample in 11 dry 100-nil. flask are added 10 nil. of a l5yOsolution of acetic anhydride in dioxane containing 2% fluohoric acid. The mixture is heated for 5 minutes on a water bath and then titrated with 1 N sodium hydroside solution. This procedure can be adapted to the determination of water in a sample by decomposing the excess acetic anhydride with 5 nil. of 3 30yosolution of triethanolamine in alcoliol and then carrying out the tit rntion with sodium hydrmide. AL1)EIIYDES A 3 D KETONES
The Iiytiroxj-lamine number, defiucd as the, numbc,r of nilligrams of potassium hydroxide e q u i v ~ l e n t o the hydroxylamine rcquirctl to osimate the carbonyl function in 1 gram of sample, appears to Ge n useful piece of data for thc idcntifictttion or quantitativc ttctcwnination of carbonyl compounds. I t is somewhat rompar:il)le to a neutralizatiori equivalent, in t h a t i t will not dist,inguish between isomers, Trozaolo and 1,irher (140) have modified the procedure of Stillman and Rerd (134) so that smaller quantitirs arc required. Under the conditions employed, no r e a d o n kict\veen hydroxylaniinr~and ester groups occurs and t,he procedure gives satisfactory results nith such compounds as ethyl acetoacetate and its derivatives. Bldehydcs may be determined in the prescnce of ketones by quantit,atively oxidizing the aldehydes to acids with silver oxide (93). The result,ing acids are determined b y titration with standard alkali. Peroxides, sodium methylate, acids, and esters have been found to interfcrc. iicetone, methyl ethyl ketone, diethyl ketone, and acetophenone do not, interfere, h u t cyclohexanone reacts to a slight extent,. Acids interfere by consuming an equivalent amount of alkali. This can be corrected for by titrating the acid-uldehyde mixture n i t h sodium methoxide in dry methanol. Esters and alcohols may also be determined i n the presence ~f aldehydes. Esters are determined after converting carbonyl compounds to oximes, and alcohols are determined after removal of aldehydes with either silver oxide or sodium bisulfite. Pornialdehyde has been determined in the presence of ketones and krto :i,li*oholsby the following proredurc (1D).
V O L U M E 2 3 , NO. 1, J A N U A R Y 1 9 5 1 To 10 ml. of a solution containing less than 0.15 gram of formaldehyde are added 10 ml. of K2HgIk solution (2.8% mercuric chloride and 7.5% potassium iodide) and 6 ml. of 2 N sodium hydroxide solution. T h e mixture is agit)ated 5 minutes, and 7.5 ml. of 2 N acetic acid and 10 ml. of methanol are added. The precipitate is removed by filtration and after washing with methanol and water is reacted with 20 ml. of 0.1 N iodine solution. The excess iodine is titrated with 0.1 S thiosulfate solution.
In another procedure for formaldehyde ( 3 ) the precipitate formed by mixing Xessler reagent with the sample is acidified with 2 S :icetic acid and treat,ed \yith a measured excess of 0.1 S iodine solution. The excess iodine is determined by titration with standard thiosulfate. (larbonyl groups may be determined in the presence of organic acids by reaction with a solution of hydroxylamine hydrochloride in 80% ethyl alcohol previously adjusted to pH 2.50 (131). At this p€€ c:trboxylic acids scarcely interfere, but the hydrochloric acid which is liberated in the reaction may be titrated stoichiometrically. Thymol blue indicator is used and the hydrochloric acid freed is titrated after 15 minutes a t room tempera.turr with 0.5 A- sodium hydroxide solution to an end point which must be carefully matchrd with a blank, or the titration may b(>carried out potentiometrically. The hydroxylamine hydrochloride reagent must be carefully adjusted to p H 2.50 * 0.01 Kith a pII meter. This reagent is sufficiently acid to catalyze the hydrolysis of acetals and ketals a t 100’ C. Only free carbonyl compounds will react a t room temperature, but acetals and ketals may also be determined if the reaction mixture is heated to 100” before titration. When aldehydes nre determined, the alkali is equivalent, mole for mole, to the aldehydr present, hut with kctones a correction factor (usually 1.030) is wcessary. The following procedure ha: heen recommended ( 9 4 ) IIR suitable for permanganate d(+rmin:ition of formaldehyde. ICxcess permanganate is added to a sodium carbonate solution of the sample and allowed to stand for 20 t o 30 minutes. The mixture is acidified with 7 1V sulfuric acid and immediately backtitrated with 0.1 N Illohr’s salt solution. An excess of hlohr’s salt is used and tjhat excess is titrated with 0.05 to 0.1 N potassium permanganate. Results with this method check within 0.01 yo. Methanol int>erferes. I t has been reported (38) that formaldehyde in hesamethylenetetramine may be determined by t,he iodometric method of Romijn ( l l S ) , if a t least a 0.1 Niodine solution is uwd. I n a study of the decomposition of a-diethylaminoisobutyronitrile (log), the acetone formed was determined by the method of Marasco (86), in which the acidity developed by reaction ait’h hydroxylamine hydrochloride is titrated with standard alkali. The reaction is incomplete in 5 minutes, but this can be corrected by using a factor of 1.05. AMIDES
The term “amide number’’ has been defined as the number of milligrams of potassium hydroxide equivalent to the nitrogen base in 1 gram of sample. Easily volatile and steam-volatile bases formed from hydrolysis of amides may be determined by distillation into standard acid (98). Nonvolatile amines have been determined by a previously published method (99).
69 in amounts up to 3% of the original solvent. It appears that chlorobenzene and acetonitrile are better solvents than acetic acid for the titration of bases. The presence of dioxane or alcohol causes a poor end point and high results, but it is reported (43’) that such 01 ganic bases as alkyl amines, pyridine, 2,6lutidine, 2,2’-bipvridine, l,lO-phenanthroline, and brucine mav be dissolved in either dioxane or ethyl ether and t i t r a k d with a dioxane solution of perchloric acid. hfodified methyl orange or methyl red is used a i t h dioxane solutions and methyl red is used with ether solutions. Methyl caffeine, codeine, sodium snlicvlate, and sodium benzoate can be titrated in acetic acid with 0.2 aV ptoluenesulfonic acid, using crystal violet indicator and taking the appearance of a green color as the end point. Caffeine, theobromine, acetanilide, and ergot alkaloids cannot be determined in this way (68). Amino nitrogen in aromatic amines has been determined by a modification of the Van Slyke procedure, in which the sample is treated with 10% hydrochloric acid and 5% sodium nitrite for 5 minutcs a t 120” to 130” (148). The amino m d groups in polyamides have been titrated with p t o l u e n e d f o n i c acid in m-cresol ( l d l ) . AhlINO ACIDS
Th(s procului
