454
ANALYTICAL EDITION
Vol. 6 , No. 6
Taylor, and Chichester (11). The factor of environmental temperature during storage should be considered in this connection. A biological test with rats was conducted by Caldwell and Johnson (1) in this laboratory. Twelve rats, each fed 60 mg. of the leaf meal per week, made an average weekly gain of 5.7 grams, indicating a value of considerably more than 100 Sherman units per gram. Small portions of this dehydrated leaf meal were treated in various ways. The decrease in carotene resulting from irradiation by a quartz mercury lamp (sample 1-a) was probably caused more by the oxidizing activity of the ozone than by the irradiation. The samples exposed to sunlight (1-b, I-c, and 1-d) were s read out in a thin layer in trays covered with window glass; tgey were then placed on a roof where they received sunlight (October) from 8:OO A.M. to 5:OO P. M., and were stirred twice daily. Bleaching occurred, so that the samples could be readily placed in order of time of exposure on the basis of the green color. The degree of greenness has, however, serious limitations in indicating the relative carotene content of different Sam les, es ecially when leaf meals are compared with meal made Hom wRole plants. SAMPLE2. Sample 2 was fine-stemmed, fairly leafy alfalfa hay cured under average conditions of exposure involvin considerable bleaching. It was chopped and stored in a darf loft. Sample 2-a was taken after 5 months of storage. SAMPLEB 3 AND 4. Alfalfa-meal samples 3 and 4 were prepared by a commercial concern, whose records show that the hay was cut after 24 days' growth, from adjoining checks in the center of a field. The hay for both lots was cut at the same time (7:30 to 8.00 A. M.). The lot to be dehydrated was immediately raked into windrows and loaded on trucks. It was dehydrated at 9:OO A. M. and milled and sacked at 1O:OO A. M. The field-cured lot was raked into windrows at 9.00 A. M. and cocked at 11:OO A. M.; the cocks were turned at 8:OO the following morning. At 4 00 P. M. it was loaded on trucks to be hauled to the mill, there it was ground and sacked at 9:00 the second morning. Thus the field-cured hay was exposed to sun in the swath only 1 hour and in the windrow and cocks about 24 hours. High summer temperature and dry air found in the interior valleys of California make possible such rapid curing. Samples of these lots were graded in Washington by officials in the Bureau of Agricultural Economics as follows:
The carotene determinations show the rapid decrease under exposure to sunlight and air, and the great variability in carotene content of hay that may occur under different conditions of curing. Comparison of samples 3 and 4 shows that under favorable conditions a field-cured product may closely approach dehydrated meal in vitamin A value. Little or no loss, apparently, occurs in vacuum drying for 3 hours a t 100" C. The high value of fresh or vacuum-dried leaves compared with commercially dehydrated leaf meal indicates that relatively large losses occur in this process. The highest carotene content thus far found in dehydrated alfalfa-leaf meal was 25.3 mg. per 100 grams of sample.
Sample 3. U. S. No. 1 extra green, fine alfalfa meal, green color 83 per cent. Sample 4. U. S. No. 1 fine alfalfa meal, green color i 4 per cent.
RBCZITZD July 9, 1934. Part of an investigation on the relation of nutrition to reproduction in livestock which became coBperative with the United States
LITERATURE CITED Caldwell, R. W., and Johnson, H. C., Calif. Expt. Sta., unpublished data. Euler, B. v., Euler, H. v., and Hellstrom, H., Biochem. Z.,203, 370 (1928).
Euler, H. v., Demole, V., Karrer, P., and Walker, O., Helv. Chim. Acta, 13, 1078 (1930).
Frapps, G. S., and Treichler, R., Texas Agr. Expt. Sta. Bull. 477 (1933).
Guilbert, H. R., and Hinshaw, W. R., J . Nutrition, 8, 45 (1934). Karrer, P., and Schlientz, W., Helv. Chim. Acta, 17, 7 (1934). Kline, 0. L., Schultze, M. O., and Hart, E. B., J. Biol. Chem., 97, 83 (1932).
Kuhn, R., Brochmann, H., Scheunert, A., and Schieblich, M., 2. Phgsiol. Chem., 221, 129 (1933).
Moore, T., Biochem. J., 24, 692 (1930). Moore, T., Ibid.,27,898 (1933). Russell, W. C., Taylor, M. W., and Chiohester, D. F., New Jersey Agr. Expt. Sta. Bull. 560 (1934). Rydbom, M., Biochem. Z.,258, 239 (1933). Schertz, F. M., Plant Physiol., 3, 211 (1928). Smith, J. H. C., and Milner, H. W., J. Bid. Chem., 104, 437 (1934).
Sprague, H. B., Science, 67, 167 (1928).
Bureeu of Animal Industry, July 1, 1929.
Determination of Carbonyl Compounds by Means of 2,4-Dinitrophenylhydrazine HAROLD A. JDDLESAND CARROLL E. JACKSON, University of New Hampshire, Durham, N. H. N A COMPARATIVE study of methods for the estima-
I
tion of carbonyl compounds, Feinberg (4) contrasted the completeness of reaction between cert,ain aldehydes and bisulfite, their reaction with neutral sulfite, and the precipitation as hydrazones produced by p-bromophenylhydrazine and p-nitrophenylhydrazine. Since that time the more highly substituted derivative, 2,4-dinitrophenylhydrazine,has been employed as a qualitative reagent by Brady (2) and Allen (1). From a quantitative standpoint this reagent would be expected to produce hydrazones of very low solubility, so that it has recently been used by Simon (9) and Reynolds, Osborn, and Werkman ('7) in estimating furfural obtained from pentosans; by Fernandez, Socias, and Torres (6) in determining camphor, menthone, pulegone, and citral; by Clift and Cook (3) for certain ketonic acids; and by Houghton (6) for the estimation of benzaldehyde. In the present work, the usefulness of 2,4-dinitrophenylhydrazine as a quantitative reagent has been extended to the
determination of a series of representative and common aldehydes and ketones.
EXPERIMENTAL The experimental work may be divided into two parts; first, a study of the conditions affecting the precipitation of the hydrazone, and secondly, the development of a general method based upon these findings which was applied t o a series of aldehydes and ketones, both aliphatic and aromatic. The general procedure followed in studying the various factors affecting the reaction was as follows: A definite weighed sample of purified and redistilled benzaldehyde was dissolved in water and an aliquot sample taken which would contain approximately 37.0 X 10-5 moles. This sample was added to the freshly prepared precipitating a ents which contained a definite amount of saturated 2,4-dinitropfenylhydrazine in 2 N hydrochloric acid, varying one at a time, the time for complete reaction, the temperature, the quantity of precipitating agent, and the extent of dilution. The hydrazone was then filtered into Gooch crucibles, washed with 2 N hydrochloric
I N DUSTR I A L A N D EN GINEER I N G CH EM I STR Y
November 15,1934
acid and then with water, and dried in a partial vacuum (about 90 mm.) at room temperature over sulfuric acid. I n Table I, the first series indicates the quantity of hydrazone formed from the known sample with three different amounts of the precipitant 2,4-dinitrophenylhydrazine, varying from slightly greater than an equivalent amount to an approximately 200 mole per cent excess. I n each group the reaction mixture was allowed to stand a t constant temperature for varying lengths of time-1, 24, 60, and 96 hours. I n these runs as the length of reaction time increased the recoveries of hydrazone progressively decreased from 99.15 down to 93 per cent of the theoretical. These results indicate that the hydrazone may undergo hydrolysis in the acidic medium and the resulting carbonyl compound may then become oxidized or escape if volatile in character. At the same time the increase in the quantity of precipitant improved the total recovery of carbonyl compound as its hydrazone from 97 per cent to a practically theoretical value of 99.15 per cent,. I n the second series similar runs were made, employing temperatures of 0", 50", and 60" C. and allowing the reaction to proceed for one hour. The results in these cases definitely favor the low temperature. Finally, as shown in the third group, a markedly increased dilution of the reaction mixture after precipitation had no appreciable effect on the recovery of hydrazone. Since this is the case, it is possible to employ samples of varying concentrations, a practice which is often necessary because of the solubility variation among organic carbonyl compounds. TABLE 1. RESULTSOF CHANGE OF CONDITIONS IN THE DETERMINATION OF BENZALDERYDE VOLUME
OF
2,4-DI-
NITROPHENYL HYDRA.. 51NEa
cc.
VOLUME OF
ALDE-
HYDEb
cc.
WDIGHT OF
TOTAL VOLUME
cc.
PRE-
TBMPERATIJRD
'C.
TIMD Hours
PRD-
CIPITATD
CIPITATION
Gram
%
60 cc. The reaction mixture was allowed to stand for one hour in an ice bath. At the end of this time a definite precipitate had formed and could be filtered, then washed with 2 N hydrochloric acid and water, and finally dried over sulfuric acid in a partial vacuum. This procedure was used t o study the precipitation of the hydrazones of acetaldehyde, acetone, methyl ethyl ketone, methyl n-propyl ketone, benzaldehyde, salicylaldehyde, p-hydroxybenzaldehyde, anisaldehyde, and vanillin. The results are given in Table 11. TABLE 11. DETERMINATION OF HYDRAZONES V o._ r-
13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6
33.6 38.6 63.6 33.6 38.6 63.6 33.6 38.6 63.6 33.6 38.6 63.6
0 0
0 Room temp. Room temp. Room temp. Room temp. Room temp. Room temp. Room temD. Room temp. Room temp.
1 1 1 24 24 24 60 60 60 96 96 96
BFFECT OP TEIMPBRATURE
20 20 20 25 25 25 50 50 50
13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6 13.6
33.6 33.6 33.6 38.6 38.6 38.6 63.6 63.6 63.6
0 50 60 0 50 60 0 50 60
97.55 93.78 91.99 98.59 93.31 92.08 99.25 93.40 92.18
METHOD OF ANALYSIS The optimum conditions, as determined in the foregoing experiments on benzaldehyde, were incorporated in a general procedure for the determination of carbonyl compounds by precipitation as the 2,4-dinitrophenylhydrazones. A measured sample of the aqueous solution containing a weighed quantity of the carbonyl compound was added dropwise to the mturated 2 N hydrochloric acid solution of 2,4-dinitrophenylhydrazine which was varied in quantity from 20 to
OF
HYDRA-
ZONE
cc.
cc.
50 50 50 50 50 50 50 50 50
25 25 25 25 15 15 15 15 15
38.76 X 10-6 mole/sample
50 50 50 50 50 50
11 11 11 11
38.41 X 10-5 mole/sample
Methyl ethyl ketone b. p. 79-80' C. (Ekstman)
40 50 60
10 10 10
36.56 X 10-6 mole/sample
Methyl n-propyl ketone, b. p. 100-101" C. (Eastman)
50 50 50 50 50 50 50 50
15 15 15 15 15 15 15 15
35.81 X 10-6 mole/sample
p-Hydroxybenzaldehyde, m. p. 116-117' C. (Eastman)
20 25 30 35 40 50 60
18.6 37.14 X 10-8 18.6 mole/sample 18.6 18.6 18.6 18.6 18.6
Salicylaldehyde b p 73-74O C. at io'mm. (Eastman)
20 25 30 35 40 50 60
15.3 37.22 X 10-5 15.3 mole/sample 15.3 15.3 15.3 15.3 15.3
Anisaldehyde, b. p. 130-131O C. at 15 mm. (Eastman)
20 25 30 35 40 50 60
14.6 37.05 X lo-' 14.6 mole/sample 14.6 14.6 14.6 14.6 14.6
Vanillin (Kahlbaum)
35 40 50 60 35
9 . 8 37.02 X 10-6 9.8 mole/sample 9.8 9.8 13.5 36.67 X 10-6 13.5 mole/sample 13.5 13.5
Acetaldehyde, b. p. 20-22O C. (Eastman)
Acetone, purified by NaI method of Shipsey and Werner (8)
51.15 X 10-6 mole/sample
11
11
Gram 0.0823 0.0816 0.0815 0.0814 0.1102 0.1101 0.1099 0.1096 0,1091 Av. 0.0894 0.0886 0.0895 0.0884 0.0891 0.0896 Av. 0.0907 0.0902 0.0895
Av.
EFFBCT OP DILUTION
Diluted to Give 13.2C 68.2 50 13.2C 73.2 50 13.2C 78.2 50 13.2C 83.2 50 13.2C 88.2 50 13.2C 93.2 50 13.2C 98.2 50 13.20 103.2 50 5 4.2 mg. per 00. b 37.11 X 10-6 moles per sample. c 29.51 X 10-6 moles per sample.
WEIGHT
UME VOLOF UME HYOF DRA- .4LD€lZINEa HYDE
DFFDCT O F TIMD AND CONCENTRATION
20 25 50 20 25 50 20 25 50 20 25 50
455
40
50 60 a
4.2 mg. per
PRmCIPITATION
% .94.82 94.01 93.90 93.78 96.16 96.08 95.90 95.64 95.09 95.04 97.82 96.94 97.93 96.72 97.49 98.04 97.49 98.48 97.94 97.18 97.87
0.0934 0.0935 0.0932 0.0938 0.0939 0.0931 0.0934 0.0951 Av. 0.1108 0.1114 0.1114 0.1113 9.1119 0.1119 0.1119 Av. 0.1095 0.1105 0.1103 0.1105 0.1117 0.1121 0.1119
98.01 98.11 97.80 98.43 98.53 97.69 98.01 99.79 98.29 98.75 99.29 99.29 99.20 99.73 99.73 99.73 99.39 97.42 98.31 98.13 98.31 99.38 99.73 99.56 AY. 98.69 0.1161 99.15 0.1166 99.57 0.1171 100.00 0.1180 100.77 0.1177 100.51 0.1177 100.51 0.1183 101.02 Av. 100.22 0.1255 0.1266 0.1268 0.1271 0.1257 0.1233 0.1244 0.1252
102.12 103.01 103.17 103.42 102.28 100.33 101.22 101.87 Av. 102.18
00.
The data for the aliphatic compounds indicate that the recovery of aldehyde or ketone as the hydrazone varied from 95.04 to 98.29 per cent, increasing as the molecular weight of the compounds became higher. The efficiency of the method was very satisfactory with aromatic compounds except in the case of vanillin which gave high results apparently due to occlusion. This error could not be lessened by repeated washings and care in precipitation. I n comparison
Vol. 6, No. 6
ANALYTICAL EDITION
456
The precipitate was filtered, washed with 2 N hydrochloric acid and water, and dried in a vacuum a t room temperature. Determinations of the amounts of hydrazone produced from samples of nine aldehydes and ketones were made and compared with the known theoretical values with variations of -4.96 per cent for acetaldehyde, -2.51 per cent for acetone, -2.13 per cent for methyl ethyl ketone, -1.71 per cent for methyl n-propyl ketone, -0.85 per cent for benzaldehyde, -0.61 per cent for p-hydroxybenzaldehyde, - 1.3 per cent for salicylaldehyde, +0.2 per cent for anisaldehyde, and $2.18 per cent for vanillin.
with the two substituted hydrazines studied by Feinberg, pnitrophenylhydrazine and p-bromophenylhydrazine on the same aromatic aldehydes, the 2,4-dinitrophenylhydrazine produces the hydrazone in quantities more uniformly approaching the theoretical values, as shown in Table 111.
TABLE 111. DETERMINATION OF HYDRAZONES P-NITROPHENYLHYDRAZINP
p-BROMO-2,4-DINITROPHENYL HYDRAZINP
HYDRABINa PHENYL-
% 99.2 98.7 99.4 100.2 102.2
LITERATURE CITED (1) Allen, J . Am. Chem. soc., 52, 2955 (1930). (2) Bradv. J . Chem. SOC..1931. 756. (3) Cliftand Cook, Biochem. i.,26, 1800 (1932). (4) Feinberg, Am. Chem. J.,49, 87 (1913). ( 5 ) Fernandez, Socias, and Torres, Anales SOC. espaa. Qs. qutm., 30, 37 (1932). (a) Houghtonv Am. J. Pharm.* 62 (7) Reynolds, Osborn, and Werkman, Iowa State Coll. J . Sci., 7, 443 (1933). (8) Shipsey and Werner, J . Chern. SOC.,103, 1255 (1913). (9) Simon, Biochem. Z.,247, 171 (1932).
CONCLUSIONS A study has been made to determine the optimum conditions for the quantitative estimation of carbonyl compounds as their 2,4-dinitrophenylhydrazones. I n the experimental determinations, a dilute aqueous solution of the carbonyl compound was added to an excess of 2,4-dinitrophenylhydrazine in 2 N hydrochloric acid, and the reaction mixture was allowed to stand a t a temperature of 0" for one hour.
c.
RECEIVED July 21, 1934.
Determination of Small Quantities of Antimony in White Metals A Volumetric Method C. W. ANDERSON,Continental Can Co., Inc., Chicago, Ill.
A
METHOD for determining antimony 'accurately has been developed in this laboratory as applied to solder, pig tin, and lead analyses, in which the antimony content is usually below 0.10 per cent. Tin and lead of high purity are used in the manufacture of solder for canmaking purposes; the antimony content is uniformly low, about 0.05 to 0.08 per cent. It was on account of the tendency toward low and erratic results obtained by the available methods that the present investigation was undertaken. Valuable suggestions were obtained from a paper by Rowel1 (6). The method as applied in the routine of white metal analysis is as follows: Weigh a 1.5-gram sample of filings, which has passed through a 30-mesh sieve, into a 300-cc. tall-form beaker. Add 15 cc. of conoentrated hydrochloric acid and 5 cc. of a saturated solution of pure bromine in concentrated hydrochloric acid (prepared by vigorously shaking 12 cc. of pure bromine with 100 cc. of hydrochloric acid in a glass-stoppered bottle). All tin-lead solders dissolve readily in this mixture. Tin will dissolve in hydrochloric acid alone, but the bromine solution should be added to insure
complete oxidation. Add more bromine solution from time to time as indicated by the disappearance of the yellow color of free bromine. When solution of the sample is complete, there should be a slight excess of free bromine Evaporate the solution to a volume of 10 cc. or a little less, and add 0.5 gram of anhydrous sodium sulfite, followed by 10 cc. more of concentrated hydrochloric acid. Evaporate again to a volume a little less than 10 cc., completely dispelling any arsenic present. Now add 20 cc. of concentrated hydrochloric acid and 40 cc. of water and boil for 1 minute while a current of air is passed through the solution. Before the final step of titration, add 60 cc. of water and titrate at a temperature of not less than 60' C., as described below. Care should be exercised when boiling the solution to expel the last traces of sulfur dioxide. As a precautionary measure, to minimize the loss of antimony, it is best t o cover the beaker with a fairly well fitting cover glass during the brief interval of boiling and agitation with the air current. The boiling need not be continued for more than a minute. Good results have been obtained by boiling for only 0.5 or 0.75 minute. For standardizing 0.0125 N potassium bromate solutian, the following procedure was developed:
TABLEI. RESULTSOF EXPERIMENTAL ANALYSES SAMPLP
6 7 8 9 10 11 12 13 14
50-50 Solder from another laboratory Tin, Bureau of Standarda, No. 42b Same as in experiment 6 Lead, Continental Can Company Tin Bureau of Standards No. 42b LE& continental Can Cbmpany Tin, bureau of Standards, No. 42b Tin Bureau of Standarda No. 42b Tin: analysis of sample 4ib
W~IQHT OF
SAMPLB
ANTIMONY ADDED
ANTIMONY ORIGINALLY PR~SENT
TOTAL PRPSENT ANTIMONY
Gtoms
Mn.
Mg.
1.0 1.0 1.0 1.5 1.0 1.0 1.0
0.80 0.55 1.3
0.20 0.20 0.20
1.00 0.75 1.50
0:b5
0.80 0.60 0.65
O:i6 0.24 0.20 0.24
o:i1 1.04 0.80 0.89
O:i5 0.95 0.96 0.90
0:io 0.10 0.20 0.20
1:65 1.05 1.15 1.10
1.0
1.5 1.0 1.0 1.0 1.0 1.5
..
..
9.
..
0.0125 N KBr03 TITRATION U8ED IN
.4NTlMONT
FOUND
CC.
Mo.
1.44 1.01 1.97 0.50 1.01 1.34 1.05 1.11 0.20 1.47 1.32 1.39 1.44 0.412
1.096 0.769 1.50 0.385 0.78 1.02 0.81 0.85 0.157 1.1 1.0 1.09 1.096 0.313
