Determination of Aromatic Nitro Compounds W. B. KONlECKl and A. L. LlNCH Medical Division Industrial Hygiene Laboratory, Chambers Works, E. 1. du Pont de Nemours & Co., Inc., Penns Grove,
b Formamidine sulfinic acid (thiourea dioxide) under alkaline conditions reduced aromatic nitro compounds to satisfactory yields of primary aromatic amines in the concentration range of 5 to 50 mg. per liter. Diazotization and coupling of the aromatic amine to Chicago acid permitted quantitation as an azo dye b y light transmittance measurement in the region of maximum absorption. Conditions required to attain the sensitivity and precision needed for evaluation of exposure in manufacturing areas through urine analysis were established for nitrobenzene, nitrotoluenes, chloronitrobenzenes and toluenes, alkoxynitro derivatives, nitrobiphenyls, nitronaphthalene, dinitrobenzene, dinitrotoluene, dinitrochlorobenzene, and nitroacetanilides. Acetylated aromatic amines did not contribute significantly to the total primary amine content during reduction.
S
1951, routine determination of urinary nitrobenzene and its derivatives in the range of 5 to 50 mg. per liter (p.p.m.) has been used by the Chambers Works Medical Division t o supplement blood hemoglobin analysis in the evaluation of exposures to aromatic nitro compounds which cause cyanosis. The method chosen from available procedures (7, 8, 11) was zinc reduction of the nitro group in acidified urine. Spectrophotometric determination of the primary aromatic amine as a red azo dye was carried out after diazotization and coupling (5, 7 , 10-12) to 1-amino-8-hydroxynaphthalene 2,4-disulfonic acid (Chicago acid) (8, 7 ) . However, this procedure also included primary aromatic amines derived from acid hydrolysis of acetylated aniline derivatives and glucuronides from protein metabolism (tryptophan degradation) (S), as well as biochemical reduction of a significant fraction of absorbed nitro compounds. lledicinal compounds, such as the sulfanilamides, headache remedies containing acetanilide and phenacetin, and Pyridium, frequently introduced complications difficult to resolve. A similar situation was met in the commercial iron reduction and hydrogenation of aromatic nitro compounds. In these operations, mixed exposure conditions provided relatively large amounts of diazotizable amino derivaINCE
1 134
0
ANALYTICAL CHEMISTRY
tives as well as nitro derivatives for urinary excretion. As laboratory experience has shown that exogenous aromatic amines are almost completely acylated before excretion, analytical conditions which avoid hydrolysis would simplify the reduction procedure (2, 6 , IS). Additional complications arose in applying zinc reduction to o-nitrobiphenyl, o-nitrotoluene, and nitronaphthalene. Low yields of diazotizable amines reduced the sensitivity below required levels. The zinc reactivity effect introduced by the o-methyl group in the phenyl ring and lack of good correlation betn-een blood and urine analyses emphasized the need for a reducing agent effective in neutral or mildly alkaline medium. Conventional alkaline systems, such as ainmoniacal zinc, sodium sulfide, sulfite, hyposulfite (hydrosulfite), and hypophosphite, did not yield acceptable results. Aqueous alkaline sodium borohydride a t the boil demonstrated efficient reduction, but the need for reflux apparatus and the hazard created by hydrogen evolution made this procedure unattractive. The reported reducing properties of formamidine sulfinic acid, thiourea dioxide (TUO), derived from hydrogen peroxide oxidation of thiourea (I, 9 ) , suggested fruitful application as a reliable, rapid, and direct analytical procedure specific for aromatic nitro compounds. Concentrations of 3 to 4 mg. per ml. in 1 to 370 aqueous alkaline buffer, such as sodium carbonate, effectively reduced 5 to 150 y of nitrobenzene. nitrotoluenes and their chloro derivatives, nitronaphthalene, nitrobiphenyls, alkoxynitrobenzenes, and nitroacetanilides in 10 to 15 minutes a t 50" C. The excess reducing agent was destroyed by heating a t 50" C. under acid conditions to prevent loss of aromatic amine in the diazotization step. The diazonium derivative coupled xith Chicago acid t o produce a red azo dye which then was quantitated by determination of light transmittance. Based on calibration curves prepared from known concentrations of the corresponding aromatic amines, reproducible yields in the range of 70 to 95% were obtained. Yields from o-methyl and phenyl derivatives were superior to results from zinc reduction in dilute acid.
N.1.
REAGENTS
All solutions must be sediment-free. FORJIAMIDISE SULFINIC ACID(Manofast salt), purchased from Hardman and Holden, LIanox House, Manchester, England. Purify by dissolving in five parts of 1.1% aqueous sodium bisulfite solution a t 60" to 63" C., clarifying, and recrystallizing slowly with agitation at 10" C. Dry the filter cake imniediatelg a t 60 =t3" C. Titration of a 1% solution in 0.3y0 aqueous sodium hydroxide a t 50" C. into alkaline 0.33N Rubine R [2-(l-naphthylazo)-lliydroxy-4,4'-disulfonic acid] indicated 98 to 100% purity based on 108 molecular weight. CHICAGOACID. Dissolve 0.5 gram of 1-amino-8-riaphthol-3,4-disulfonic acid in 1 ml. of 37% hydrochloric acid and 45 ml. of distilled water. Dilute to 50 ml. with distilled water. Store in a refrigerator and avoid exposure to light. Discard after the third day. SODIUM KITRITEREAGENT, 3% aqueous solution. Discard when color appears any darker than a faint lemon yellow. This reagent is stable for approximately 2 weeks. SODIUM ACETATE BUFFER. Dissolve 320 grams of sodium acetate trihydrate in 1000 ml. of distilled water. PROCEDURE
For each 5-nil. increment of urine in a large test tube (50 X 200 mm.), add 3 ml. of 10% sodium carbonate and 20 to 25 mg. of formamidine sulfinic acid, and dissolve by swirling. Loosely cap the test tube to reduce evaporative losses, and heat for 15 to 20 minutes in a water bath a t 50" rt 5" C. with occasional agitation by swirling. Add 1.5 ml. of 10% hydrochloric acid while swirling, replace the cap, and heat a t 50" i: 5" C. for 5 to 10 minutes to destroy excess formamidine sulfinic acid. Chill to 0" to 5" C. in an iced water bath for not less than 10 minutes, add 1.5 nil. of 10% hydrochloric acid, swirl to mix rapidly, and complete the destruction of excess formamidine sulfinic acid. Immediately add 10 ml. of distilled water and mix; Diazotize a t 0" to a C. by adding 1 ml. of sodium nitrite reagent and mix by swirling. After 3 to 5 minutes, destroy the excess nitrous acid by adding 1 ml. of 10% sulfamic acid reagent. Rlix thoroughly, let stand a t 0" t o 5 " C. for 18 to 20 minutes, and test for nitrous acid bg spotting on cadmium iodide starch paper. If a positive test appears, add 1-ml, aliquot of sulfamic acid reagent and let stand another 20 minutes. This 18- to 20-minute waiting period is necessary for complete de-
composition of all persistent nitrite complexes which may arise from the reaction of nitrous acid with formamidine sulfinic acid decomposition products. Divide the solution equally into two 25-m1. volumetric flasks, and add 0.5 ml. of Chicago acid reagent t o one aliquot. Add 5 ml. of sodium acetate reagent to each aliquot and mix by swirling. Heat at 50" =t 5" C. for 15 to 20 minutes to ensure complete color development and dilute t o volume with distilled water. Kithin 4 hours after coupling, determine light transmittance a t the appropriate maximum absorption n a v e length for the azo dye derived from the aromatic amine produced by reduction of the nitro compound against the blank (the aliquot to which no Chicago acid mas added). The micrograms of nitro compound sought (nitrobenzene, if the identity is not known) were read from a semilog calibration chart based on k n o r n quantities in aliquots taken from a standard solution. These aliquots were taken from a stock solution made by diluting 20 ml. of C.P. methanol, containing 500 y of aromatic nitro compound per milliliter, to 100 nil. with C.P. methanol (100 y per i d ) . A Beckman Model D U spectrophotometer was used to collect data given in Table I. Calculation. RIg. of nitro compound per liter = y found X 1000 y found vol. of sample x 1000 vol. of sample Zinc Reduction. Measure 25 ml. of urine into a 250-ml. beaker; add 2 ml. of 37% hydrochloric acid and 0.1 t o 0.2 gram of zinc dust. K i t h intermittent stirring, heat t o 55" t o 60' C. a n d maintain temperature for 10 t o 15 minutes. Cool t o 20" t o 25' C., a n d filter off t h e excess zinc on glass fiber filter paper (Hurlb u t Paper Go.) in a Gooch crucible. Rinse the filter with 5% hydrochloric acid (total combined filtrate volume should not exceed 40 ml.). Transfer the filtrate t o a 50-ml. volumetric flask, and dilute t o volume with distilled water. Transfer two 10-ml. aliquots to each of two 50-ml. volumetric flasks and proceed with diazotization by adding nitrite as described for formamidine sulfinic acid reduction. DISCUSSION
To avoid interferences in the diazotization and coupling stages, the amount of reducing agent must be held to a minimum consistent with complete reduction. Formamidine sulfinic acid concentrations of 3 to 4 nig. per nil. and a 100 to 1 (by weight) reductant to oxidant ratio effectively converted nitro to amino groups. The procedure described is useful in the range of 10 to 150 y for most nitro compounds. Beyond these limits light absorption measurements fall in regions of uncertainty (above 90% or below 20% transmittance). Yields were not significantly improved by increasing the formamidine sulfinic acid concentration
Table I.
Aromatic Amines from Reduction of Aromatic Nitro Compounds (Comparison of yields based on 100 y of nitro compound) Wave . -. . Length, % Yield Max. Zinc T U 0 Absorp., The- reduc- reducSitro Compound Amino Compound illr orya tion tion SO. 520 76 88 91 1 Sitrobenzene Aniline o-Toluidine 535 78 55 82 o-Sitrotoluene 2 550 78 7.3 81 p-Xitrotoluene p-Toluidine 520 81 86 80 o-Xitroc hlorobenzene 0-Chloroaniline 530 81 81 82 p-Nitrochlorobenzeiie p-C hloroaniline 530 84 94 80 3,4-Dichloronitrobeiizene 3,4-Dichloroaniline 520 84 83 89 2,5-Dichloronitrobenzene 2,5-Dichloroaniline 2-Chloro-&nitrotoluene 83 90 88 2-Chloro-4-aminotoluene 520 520 83 89 89 9 4-C hloro-2-nitrotoluene 4-Chloro-2-aniinotoluene 550 83 76 81 1-Nitronaphthalene 10 I-Saphthplamine 540 85 64 85 11 o-Sitrobiplienyl o--1minobiphenyl 540 85 82 81 12 p-Sitrobiphenyl p-lminobiphenyl 13 p-Kitroanisole p-hnisidine 540 80 60 50 14 p-Yitrophenetole 530 82 72 8.3 p-Phenetidine 560 82 68 68 15 4-Methy1-2-nit1oanisole Cresidine 16 oa-Xitroacetanilide 520 83 76 83 ),L-.lminoacetanilide 520 83 88 94 1 i p-Xitroacetanilide p-Aminoacetanilide 520 64 84 89 18 m-Dinitrobenzene m-I'hen ylenediamine 2,4-Tolylenediamine 520 67 94 01 19 2,4-Dinitrotoluene mol. n.t. amine. a Theory yield = 100 X mol. Lvt. nitro Table II.
Removal of Excess Formamidine Sulfinic Acid (TUO)
(Reduction time, 15 minutes) Reduction T U 0 Decomposition Conditions 10% TUO, Tzmp., HCl, Time, Tzmp., i mg. C. ml. min. C. 125 170 ... 0.5 5 50
,
Compound .\dine
2.0
3.0
0 0
5
ni-Phenylenediamine
125
170
...
Sitrobenzene
250
340
26
170
50
15
3.0 3.0
15
15
... ...
70
Yield 62 29 41
50
74 90
26 26
23 53 85 95 68 72
50
64 70
c-
iD
Dinitrobenzene
250
340 170 85
50 25
alone (Table 11). The excess remaining after reduction must be removed before complete recovery of the aromatic amine as an azo dye can be assured (Table 11). Heating at 50" to 60" C. for 5 to 15 minutes after reducing the apparent p H below 10 (Table 111) removes this interference satisfactorily (Table 11). However, immediate addition of excess acid may produce turbidity, which stepwise acidification helps eliminate. Turbidity seldom develops when heating follows the addition of up to one half of the acid required for diazotization. The indicated cooling before addition of the balance of the acid further ensures clear diazo solutions.
26 26 50 50 50
3.0 3.0 3.0 3.0 3.0
15 15
4 81
80
15
65 26 50
15 15 15
90 80 80 80
15
_15
91 39 35 45 40
81 66 89
Reduction proceeds slowly at room temperature and reaches a limit at about 70y0 conversion in 15 to 30 minutes. A thirteenfold formamidine sulfinic acid concentration increase does not improve the aromatic amine yield (Table 11), but heat shifts the conversion nearly to completion. The optimum temperature is in the range 50" + 5" C., where reduction is complete in 10 t o 15 minutes. Evaporative losses become excessive when higher temperatures or prolonged heating cycles are employed. Loosely capped test tubes minimize these losses and reduce atmospheric oxidation which cannot be tolerated in open beakers (Table 111). VOL. 30, NO. 6, JUNE 1958
1135
Table 111.
Effect of Buffers on Reduction Efficiency (100 -{ nitrobenzene basis) Glass-Calomel Electrode pH After .Sfter After 1 ml. of 3 ml. of red. HC1 HC1 3.4 1 .o 1 .o 10.1 0.8 0.4 10.5 7.4 0.7 10.7 10.4 1.8 9.4 9.6 1.8 12.8 0.G 0.6 11.0 0.9 0.5 10.2 2.8 1.9b
Alkaline Reagent Strength, Vol., Before red. ml. Compound % Xone ... .. 6.6 Il'a2C03 10 1 10.1 KaeCO, 10 3 10.9 iYa2COa 10 12.5 XaHCO7 10 10.4 SaOH " 10 12.8 Sa3P04 10 11.9 NHaOH 28 12.2 170 mg. of formamidine sulfinic acid for reduction. 3770 HCl added dropwise to acidify. ~
Table IV. Representative Urine Results (Three or more aromatic nitro compounds, or nitro and amino compounds) Sitro Analysis, Mg./Liter Aromatic lZmines*, Case Date Com- Zinc TGO Mg./ No. 1956 pounda red. red. DifT. liter Remarks 1-R 11/9 KB 4 2 - 2 ... , . . KOexposure 2-D 11/9 KB 4 5 1 No exposure 23 4 -19 Phenetidine 0165 APC medication 3-L 11/12 NB 4-L 11/13 S B 2 2 0 Phenetidine 0.41 S o exposure 5-1 11/11 S B 6 5 - 1 Aniline 0.52 KO exposure 6-L 11/21 S B 5 2 - 3 iiniline 0.16 No exposure 7-5 11/13 DKB 44 7 -37 hlPDc 10.2 Mixed exposure 8-5 11/13 DKB 9 10 1 MPD 0.52 9-T 11/13 DXB 5 12 7 ... 10-M 11/16 XB 6 5 - 1 izniline' 0.34 Unknown exaosure 16 14 - 2 ... , . , Mixed expostre 11-W l l i l 5 KB 12-G 11/27 S B 2 5 3 ... , . , Mixed exposure , . . , . , Mixed exposure 12-L 11/20 KB 27 13 -14 1 7 6 ... , , , Mixed exposure 13-R 11/27 XB Mixed exposure 14-W 11/20 KB 6 6 0 Mixed exaosure 15-V 11/16 D S B 29 17 -12 Unknown- exposure 22 18 - 4 ... , .. 16-T l l j 1 4 XB 11 ... . . . Mixed exposure 17-D 11/18 DNB 2 13 i8-F i i j i 6 DXB , , Medication .4?yI 110 37 -73 . . Medication 132 60 -72 PM Diff. 22 23 1 ... . . , Increase from exposure NB, nitrobenzene. DNB, dinitrobenzene. After hydrolysis. c m-Phenylenediamine.
,
~~
0
An alkaline buffer system is required to stabilize formamidine sulfinic acid and maintain pH in a favorable range (Table 111). Sodium carbonate gave the most consistent results, but the possible advantages indicated by trisodium phosphate or ammonium hydroxide, which might permit operation in open beakers, were not fully explored. These alkaline buffer systems promoted reduction in the presence of acetylated primary aromatic amines (such as phenacetin), frequently encountered in urine analysis, without producing hydrolysis to the extent of introducing significant errors in the determination of the reduced nitro compounds (Table IV). Yields of aromatic amines from alkaline formamidine sulfinic acid reduction of ortho-alkylated aromatic nitro derivatives were superior and more reproducible than results from acidic zinc reduc-
1 136
ANALYTICAL CHEMISTRY
tions. This improvement was especially apparent in the reduction of onitrotoluene and biphenyl derivatives where amine yields increased 20 to 30y0 (Table I). The standard deviations of replicate determinations of known quantities of most of the 18 nitro compounds studied fell in the range + 5 y, which is only slightly greater than that established for aromatic amine calibration curves, i 4 y. Percentage yield was determined by reading from the amine calibration chart the micrograms equivalent to the light transmittance (as yo T) of the azo dye derived from reduction of the nitro compound, and dividing by the theoretical equivalent calculated from molecular weight ratios. Iron-free (less than 10 p.p.m.) distilled water was required to avoid formation of extraneous color on addition of the Chicago acid coupling rea-
Red. at 26" C: 68 64
... 66 64 43
% ,- Yield as Aniline Red. a t 25 M g . of TCO, 50' C., open closed beakers tubes 0 23 67 92 33 91
38
84
25 55 72
87
~~
88
89
92 87
gent. Addition of 58 p.p.m. ferrous iron to 2-chloro-4-aminotoluene before diazotization reduced the recovery 15%. Iron a t a 68 p.p.m. concentration in the reduction mixture introduced a 5% error. As the reagents are relatively dilute, use of analytical reagent grade products has controlled iron contamination within operable limits. K h e n iron is present, a nitrous acid complex not detectable by starchiodide, b u t revealed by sulfanilic acid and ll'-l-naphthyl-ethylenediamine reagent (IS), will persist in the presence of cold sulfamic acid (0" to 5" C.). Bromide ion, often added to catalyze diazotization, increased this effect strongly. Glass!\-are must be kept meticulously clean at all times. Most washing compounds and cleansers contain organic materials which adsorb tenaciously to glass surfaces. These adsorbed layers appear to retain nitrous acid, or nitrogen oxides, in a state which does not react with sulfamic acid, but does react with Chicago acid to produce a.yellow-brown or orange color. This spurious color reaction produces high results which may be sufficiently uniform t o produce false calibration curves (zero weight intersect a t some light transmittance value below 100%). Reagent blanks and paper chromatograms reveal this condition unmistakably. To avoid this nitrite-adsorbing contamination, and remove residual azo dyes which may be adsorbed t o the coupling flasks and spectrophotometer cuvettes, soak all glassware in 5% aqueous trisodium phosphate for sereral hours, and rinse thoroughly mith distilled water. Soak Corex cuvettes only in a 37% nitric acid wash, homever. Application of the formamidine sulfinic acid reduction procedure has revealed hitherto unrecognized reducible derivatives and conjugates which require further study to determine significance (Table IV, 9-T, 13-R, and 17-D). Reliability in the presence of acetylated amines was demonstrated in practice (Table IV, 3-L, 7-S, and
18-F), and was useful in determination of exposure t o nitro compounds during medication with aromatic amines (18-F). Differences between the two methods, less than zk5 mg. per liter, probably are not significant in view of the variability of natural occurring aromatic amines such as conjugated tryptophan degradation products (5). Recovery of known quantities of the aromatic nitro derivatives listed in Table I after addition to fresh urine fell in the range 50 t o 90%. The yield varied with individual donors, with the same donor from day t o day, and with t h e time elapsed between addition of the known and start of r e d u d d n . However, the corresponding aromatic amines added t o urine under similar conditions could be recovered nearly quantitatively (95 t o 100%) even after 24 hours at room temperature. Therefore, the observed nitro compound losses were not due to interferences with t h e diazotization and coupling reactions, h u t may be due t o enzyme-promoted
hydroxylation reactions which are known to occur in vivo (11, 14). Observed decrease in steam volatile derivatives, as either exposure specimens or knowns aged a t room temperature, confirms the activity of a competitive reaction system. Since presentation of this paper, the presence of p-nitrophenol in the urine from workmen exposed to nitrobenzene has been confirmed b y differentially coupling the diazotized amines from reduction at 60” and 80” C., the temperature at which p-aminophenol couples. Further study to resolve this reaction system is in progress. LITERATURE CITED
Boescken, J., Rec. trav. chinz. 55, in4n iimfii. BragLH. G., Thorpe, FV. V., Kard, P. B., Biochem. J.48,394 (1951). Brown. R. R.. Price, J. M., J . Biol. Chem. 219, 985 (1956). ’ Bushby, S. R. M., Woiwod; A. J., Biochem. J. 63,406 (1956). Elvove, E., J . Ind. Eng. Chem. 11, 860 (1919). \ - - - - I .
English, F. L., -1x.k~. CHEX 19, 457 (1947). Flemine. A. J.. D’Alonzo. C. A.. ZapG’ J. A,.,’ “hlodern ’ Occupa: tional Medicine,” p. 114, Lea & Febiger, Philadelphia, 1954. Jacobs, M. B., “Analytical Chemistry of Industrial Poisons, Hazards, and Solvents,” 2nd ed., p. 722, Interscience, Kew York, 1949. Lubs, H. A,, (to E. I. du Pont de Kemours 8: Co.), U. S. Patent 2,164,930 (July 4, 1939). Pinto, S. S., Wilson, IT. L., J . Ind. Hyg. Toxicol. 25, 381 (19q3). Von Oettingen, W. F., U. S. Public Health Bull. No. 271, pp. 4, 87, 1941. (12) Kestfall, B. B., Smith, M.I., Proc. SOC. Exptl. Biol. M e d . 51, 122 (1942). (13) Killiams, “Detoxication Mechsnis%,” %ley, Kew York, 1947. (14) Wilson, K.. llader, P. P., Palmer, L., Southern California Air Pollution Foundation Doc. 00766, 1955. RECEIVED for review June 28, 1957. Accepted January 31, 1958. Ninth Delaware Chemical Symposium, University of DelaTare, Kewark, Del., February 16, 1957.
Dete rminuti o n of Iodoform by Photooxid CI ti o n SAMEER BOSEl Department of Chemistry, Mahakoshal Mahavidyalaya, Jabalpur, India
b A procedure for the determination of iodoform was developed based on the rapid decomposition of iodoform into free iodine in visible light. All three atoms of iodine are quantitatively oxidized. The maximum amount of iodoform estimated b y this method is 0.1 gram; analytical precision is to 0.5% or better. Acetone in the presence of other aldehydes has also been evaluated b y converting it to iodoform.
A
and easy method for estimating iodoform was needed in the study of a reaction where iodoform was one of the products. It has been known for some time t h a t iodoform absorbs light in the visible region ( 1 ) . Emschwiller observed (8) that on photooxidation of iodoform, iodine pentoxide is produced, but later (3) showed that the first product of photooxidation is probably free iodine and iodine pentoxide is produced only by secondary reactions. An attempt to determine iodoform in ether by photoelectric colorimeter failed, as the faint yellow color of the solution became rapidly deeper because of iodine liberated on exposure to light. The following proPRECISE
Present address, 310 Napier Town, Jabalpur, India.
cedure is based on the quantitative decomposition of iodoform which occurs when a solution in ether-benzene mixture is exposed to bright sunlight in the presence of air. EXPERIMENTAL
All chemicals used were of analytical reagent grade except iodoform, which was C.P. Iodine solution, 0.1N and O.05N. Sodium thiosulfate solution, O.1N and 0.05N. Sodium hydroxide solution, 1. O S . Sulfuric acid solution, 1 . O N . Sodium acetate solution, 20 grams of sodium acetate dissolved in 100 ml. of water. Starch solution, 1% aqueous. Phenolphthalein solution, 1y0 stock solution prepared by dissolving 0.5 gram in 30 ml. of ethyl alcohol and diluting to 50 ml. with mater. Reagents.
Preliminary Experiments. To find a suitable solvent for iodoform, the effect of various solvents on the process of photooxidation was investigated. Iodoform solutions (0.05%) were prepared in ether, benzene, chloroform, and carbon tetrachloride, and 100 ml. of each was exposed to bright sunlight in a 250-ml. conical flask of borosilicate glass which was corked and sxirled from time to time. Benzene and carbon tetrachloride solutions developed a violet tinge and completely decomposed in 1 hour into free iodine and a n unknown gaseous product which was allowed to escape by opening the cork occasionally. The liberated iodine was titrated with 0.05X sodium thiosulfate solution after 1 gram of solid potassium iodide and starch solution had been added t o the flask. K i t h ether solution, the decomposition mas initially
Table I. Effect of Solvent on Photooxidation of iodoform (Iodine obtained from 100 ml. of 0.05% solution after 1 hour’s exposure to sunlight) Initial Rate of Iodine Obtained, RIg. S o h ent Decomposition Exptl. Theory Ether Very rapid 24.8 48 4 Benzene Rapid 48 2 48 4 48 1 48.4 Carbon tetrachloride Slow Chloroform Slow 30.0 48.4
VOL. 30, NO. 6, J U N E 1958
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