tallied by subjecting e , x h compound to the procedure used for 1-naphthol. For each of the phenols investigated, a color was formed upon addition of the iodine solution which was completely discharged on shaking with sodium hydroside and the xylene layer showed no absorbance. The addition of other phenols to solution:$ containing 1naphthol has no effc e t on the color development. The compounds investigated for pos&le interference were : 2-naphthol, phenol, 2,4-dichlorophenol, picric acid, thymol, catechol, resorcinol, hydroquinone, phloroglucinol, and 2,2'methy enebis(4 - methyl - 6 - tert - butylphenol). Although the precision of this determination is very good, the deviations of 1-naphthol from the stated value (Table IV) are all on the low side. This indicates that the method is possibly not quite quantitative as one would expect deviations both above and below the accepted value for a series of seven results.
Table IV.
Summary of Determinations
-~ 1-Naphthol (mg.)
Sample
Present 14.0 20.0
s-1
s-2 S-3 (10 nig. 2-naphthol) 10.0 5-4 (35 mg. 2-naphthol) 10.0 S-5 (10 mg. each of 2-naphthol, resorcinol, and phenol) 15.0 S-6 (10 nig. each of thymol, picric acid, and catechol) 1;i.0 S-7 (30 mg. each of 2-naphthol, resorcinol, and phenol) PO , 0 a Average of three or more determinations.
LITERATURE CITED
( l ) Afanas'ev, B' K.,
29 (1940).
Farnzatsiua
z.
( 2 ) Castiglioni, Lk.~
9-10*
ChenL. 113,
428 (1938). (3) Ghigi, E., Ann. Chim. Farm. 1939, p. 24.(4) Hercules, D. &I. Rogers, L. B., ANAL. CHEM.30, 96 (1958). ( 5 ) Malowan, L. S., Mikrochemie ver Mikrochim. Acta 38, 212 (1951).
Mean error 0.2 0.3 0.1
9.8
0.2
Relative error, yo 1.43 1.50 1.00 2.00
14.8
0.2
1.33
14.8
0.2
1.33
10.7
0.3
1.50
Foundu 13.8 19.7 9.9
(6) Nicolas, L., Burel, 12., Chint. Anal. (Paris) 38, 316 (1956). (7) Rosenthaler, L., Pharvl. zhlciu Helv. 25, 365 (1950). (8) Singh, B., Singh, Mohan, Res. Bull. Punjab Unav. 73, 73 (1955). RECEIVED February 25, 1963. Accepted July 30, 1963. Tenth Anachem Conference, Detroit, Mich., October 1962.
Coulo metiric Determination of Carboxylic Acid Hydrazides ALAN F. KRIVIS, EUGENE S. GAZDA, GEORGE R. SUPP, and PERRY KIPPUR Olin Research Center, Olin Mathieson Chemical Corp., New Haven 4, Conn.
b Coulometric brotninaiion of a variety of acid hydrazides has been studied. Bromination solutions containing acetic acid could not be used because of the apparent formation of secondary hydrazides which were not readily oxidized. Aqueous or methanolic hydrochloric acid-potassium bromide solutions permitted precise and accurate results to be obtained. Four moles of Bro were consumed per mole of hydrazide function. Some compounds containing sulfur 01' an aciivated benzene ring also showed a further reaction with bromine. The most common contaminant, the symmeirical secondary hydrazides, did not appear to interfere w th the analysis.
r
r
HL ILLCENT W I D E ~ P R E A D
INTEREST
in carbosylic acid hydrazides for a variety of applicatioiis and the subsequent growing c o m r ercial importance of different acid hydrazides led to a search for an analytical method which would be universally applicable to the determination of these hydrazides. Previous esperience had shown that a n iodate titration (2, 5 ) could be used in sume cases, a potenti2metric acid-base titration (6) could be used in other
cases, and a chloramine-?' titration ( 7 ) could be used in still other instances. No one method, however, appeared to be useful in all cases. Coulometric bromination of hydrazine and substituted hydrazines was very successfully applied to a wide variety of compounds (4). I n addition, isonicotinic acid hydrazide has been determined by a coulometric bromination (1, 8). On the basis of these reports, i t was felt that coulometric bromination offered the possibility of being a universal method for acid hydrazides. Furthermore, the automation possible with coulometric titrations would permit analyses by personnel with little scientific training and be especially useful for production control. Therefore, a study to determine the applicability and limitations of the coulometric bromination of hydrazides v\ as undertaken. EXPERIMENTAL
Apparatus. COULOMETER. Two different coulomett.rs mere used for t h e study. One conqisted of a Sargent constant current power supply (Yo. 30974) and a 10-0-10 pa. meter relay (Assembly Products, Inc.) with a 1.5volt battery and a variable resistor for the detection csircuit. The other
coulometer had a Regatron conhtant current power supply, Model C 612-X (Electronics Measurement Co., Inc.), ;\lode1 S-10 timer (Standard Electric Time Co.), and the meter relay described above. The meter relay was set to shut the power supply off a t a measured 5 pa. in the detection circuit. ELECTRODES. A coiled platinum anode and a n isolated foil platinum cathode (Leeds and Sorthrup Co.) were used as the generating electrodes, and two platinum wire electrodes were used as the amperometric detecting electrodes. The latter had 0.2 volt impressed across them via a 1.5-volt battery and a variable potentiometer (International Resistance Co.). Reagents. B R O ~ I I N A T I U G SOLUTIONS. (a) acetic acid, 607,; methanol, 26%; aqueous K B r , 147; 1M; a n d mercuric acetate, O . O O G X . (b) 0.3M HCl-O.1Jf KBr, aqueous, (e) 0.3X HC1-0.ILll KBr, 85% methanol. CHEMICALS.All chemicalr, except for hydrazides, were reagent grade and were used without further purification. The hydrazides used were the be,t grades available and either were ubed without further purification or were subjected to multiple recrystallization in cases where the materials were impure. Procedure. Place a magnetic stirring bar into a 100-nil. beaker, traiisVOL. 35, NO. 12, NOVEMBER 1963
1955
fer a n accurately weighed s:tmple containing approximately 1 mg. of hydrazide t o t h e beaker, and a d d 50 ml. of suitable bromination solution. Dip t h e electrodes into t h e solution, s t a r t t h e stirrer, a n d titrate with a generation current sufficient t o give approximately a 200-second titration. The end point is reached when a stable 5-pa. current is shown on the detection meter. R u n a blank titration and subtract the blank from the sample titration. Calculate the amount of hydrazide present from Faraday's law. RESULTS A N D DISCUSSION
Olson (4) reported that mercuric acetate catalyst in an acetic acid-watermethanol system (3) greatly increased the rate of oxidation of hydrazines and, therefore, the initial work on the analysis of hydrazides was carried out in the mercuric ion-containing bromination medium of Leisey and Grutsch (3). The results obtained for different types of hydrazides, however, did not appear t o be consistent with published data on the oxidation of hydrazines or hydrazides. None of the compounds studied showed the expected consumption of 4 moles of Bra per mole of hydrazide function; in all cases, the amount of bromide consumed was lon er than that expected. For example, stearic hydrazide consumed 1.13 moles of Bra per mole; terecarbohydrazide, 3.63 moles; phthalic dihydrazide, 3.62; and isophthalic dihydrazide, 2.80. To determine the cause of the difficulties, titrations of isophthalic dihydrazide were carried out in the absence of the mercuric ion catalyst. A small increase in the bromine consumption (from 2.8 to 3.6 Bra per mole of compound) in the absence of Hg+* was noted, but the results nere again significantly lower than expected. Other dihydrazides were tried and, in all cases, a maximum of 4 moles of Bra per mole of compound was approached, but not reached. These results indicated that the acetic acid in the bromination medium probably reacted to form a secondary hydrazide, which was not easily titrated. The reason for the reaction of the acetic acid with hydrazides, but not with hydrazines, is presently being investigated. Coulometric titrations were then carried out in a n aqueous hydrochloric acid-potassium bromide medium. Table I lists the results found with a variety of hydrazide compounds. A consumption of 4 Bro per hydrazide group was obtained with the following apparent over-all reaction: 0
/I
RCNnHs
+ 4Br + HpO 0
1956
ANALYTICAL CHEMISTRY
Table 1.
Coulometric Bromination of Acid Hydrazides in a 0.3M HCI-O.IM KBr Medium
Moles Bro/mole Calculated Compound hydrazide found purity, 7% Acetic hydrazide 4.01 100.3 Diacetyl hydrazide no reaction Adipic monohydrazide 4.28 106: 6 Adipic dihydrazide 7.99 99.8 Stearic hydrazide 2.96and3.74 73.9 and 93.6 Distearyl hydrazide no reaction ... Diglycolic dihydrazide 3.97 90.2 Cyclopropanecarboxylic hydrazide 3.85 96.7 Carbohydrazidea 7.28 90.7 Thiocarbohydrazide 11.72 96.7 Isophthalic dihydrazide 7.97 99.6 Terephthalic dihydrazide 7.73 96.6 hlonomet,hyl terephthalic hydrazide 4.00 100.0 Pnlicylhydrazide 5.54 92.9 1,z-~itrol)enzhydrazide 3.80 07.4 Isoni cotinic acid hydrazide 3.90 07.7 a ilctually hemihydrate; recalculation such gives 7.0s Ur per mole :mid a purity of 9'3.7%.
Compounds containing other reactive functional groups such as sulfur or activated benaene rings consumed more than the expected amount of bromine. Alkyl Hydrazides. T h e primary alkyl hydrazides studied-low molecular weight, high molecular weight, a n d cyclic-consumed 4 moles of BrO per mole of hydrazide function except for one case where a tfhione group was present also. No difficulties were encountered with conipounds which were water soluble. However, some materials--e.g., stearic hydrazide-were almost completely water insoluble, and a change in solvent was necessary. An 85% methanolic WC1-KBr medium was used and the sample added to the medium dissolved in toluene. Titrations of the stearic hydrazide were then both accurate and precise. For example, samples which were 75 and 94% pure were assayed coulometrically a t 73.9 and 93.6%, respectively. The major contaminant, the symmetrical secondary hydrazide, distearyl hydrazide, did not react under the conditions of the titration and, therefore, did not interfere. Acetic hydrazide also gave results similar to stearic hydrazide in the sense that the primary free hydrazide consumed 4 moles of 131-0 per mole of hydrazide, while the symmetrical secondary hydrazide, diacetyl hydrazide, did not react under the conditions of the analysis. Therefore, these data indicate that the expected major contaminant in hydrazides, the secondary hydrazides, does not readily react with bromine and, therefore, does not interfere. An assay of 106.6% was obtained for adipic monohydrazide, which was due to the presence of a small amount of free hydrazine and/or primary dihydrazide. Titration of various samples of carbo-
hydrazide from differing sources, even when recrystallized, gave results indicating approximately 90% purity. However, drying under vacuum at room temperature increased the assay to 9375, while drying at temperatures from 50" to 150" C. caused decomposition of the sample. Mass spectrometric examination of the sample indicated signscant amounts of water. A Karl Fischer water determination showed a slow reaction with the hydrazide itself, but no rapid initial reaction which would be a measure of adsorbed water. Nuclear magnetic resonance (NMR) studies also found no adsorbed water. On the basis of these results, i t appeared that carbohydrazide crystallized as a hemihydrate. Calculations using a molecular weight which included one-half mole of water then gave the expected 8 to 1 stoichiometry for the bromination reaction and also indicated a 99+% purity for recrystallized materials. Thiocarbohydrazide consumed a total of 12 BrO per mole, which indicated a reaction with both the hydrazide and sulfur groups and mas the only instance where more than the expected amount of bromine was consumed. Aryl Hydrazides. The behavior of some aryl hydrazides differed from t h a t of t h e alkyl hydrazides, since in t h e presence of a n activating group such as hydroxyl or amino i t was possible t o substitute bromine on t h e benzene nucleus. For example, salicylhydrazide consumed 6 moles of Br t o 1 mole of compound; 2 moles of Br appeared to be involved in bromine addition on the ring. The other aromatic hydrazides studied reacted with bromine in the same manner as did the alkyl hydrazides. The isomers of phthalic dihydrazide consumed 4 Rr per hydrazide function, and the half hydrazide, monohydrazide-
monomethyl terephthalate, consumed a total of 4 Br per mole of compound. In addition, the phthelate esters and hydrazides were polarographically red u c i b h and it was P3ssible to determine the amount Of by the undesired isomer .a the crude reaction product. 1sop:ithalic dihydrazide gave a wave at - 1.88 volts; ten+ phthalic dihydrazide, at -1.60 volts; and monomethyl terepllthalic hydrazide gave one wave a t -1.52 and another at 1.74 volts.
ACKNOWLEDGMENT
The authors are indebted to R. E. Bailey, R. L. Doerr, and E. J. &char of the orin Mathieson Chemical Gorp. for preparation and purification of many samples and for many helpful discussions. LITERATURE CITED
(1) Kawnmura, F., &Iom\,ki, K., $.uzuki,
S., Bull. Fac. Eng. Yokohania Nall. Univ. 4, 123 (1955).
(2) Ilolthoff, I. M., J. Am. Chem. SOC. 46,2009 (1924). (3) Leisey, F. A., Grutsch, J. F., ANAL. ( z k ~ ~ ~ ~ 1545 ~ (1960). ~ 1 ~ 5 (5) Penneman, R. A., Audrieth, L. F., fbzd., 20, 1058 (1948). (6) Sensi, P., Gallo, G. G., Ann. Chim. Rome 43,453 (1953).
( 7 ) Singh, B., Rehmenn, A., J . Indian Chem. Boc. 17, 169 (1940). (8) Szebelledy, L., Somogyi, Z.,2. Anal. Chenz. 112 (1938).
RECEIVEDfor review July 22, 1963. Accepted August 16, 1963.
Spectrographic Method for Determination of Trace Elements in Milk JOHN L. VOTH Department of Chemidry, University of California, Davis, Calif.
b Trace quantities of zinc, iron, manganese, and molybdenum have been determined in milk. The method incorporates dry ashin13 the milk and dissolving in hydrochloric acid. The trace elements, :complexed with tertcarbate (N-pyrroliditiodithiocarbamic acid-sodium salt) at pH 4 to 5, are extracted into chlorof'xm. The extract is absorbed on filter paper and the solvent evaporaied leaving the trace elements. The paper is ashed and mixed with a suitable buffer. It is then ready for spectrographic analysis. A 2000-fold increase in concentration is thus obtained.
S
extraction of trace elements results in important improvements in spectrographic analysis. Increase in sensitivity is limited only by the size of sample. The trace elements are separated from refrtictory materials that adversely affect the reproducibility of the arc; they can be burned in a matrix of constant composition with smooth arcing characteristics. The choice of the reagent, terf-carbate, is especially suitable bwause none of the extracted elements is normally present in amounts sufficient to affect the arc. The reagent is nonspecific and most trace elements will form complexes which can be extracted with chloroform. By using a large sample of milk, the effect of contaminants from resgents or containers is reduced. OLVENT
cipitation with sodium hydroxide solution the salt is washed several times with ethyl acetate and dried a t room temperature. A 75y0 yield is obtained. White crystals (0 8 gram) are dissolved in 10 ml. of water for reaction with each milk sample. A sufficient amount of solution is prepared for one day's use and this is extracted twice with chloroform to remove contaminants. Stock buffer solutions are: 5-sulfosalicylic acid, 125 grams per liter adjusted to p H 4 8 with concentrated ammonium hydroxide. Sodium acetate, 100 grams per liter adjusted to pH 4.8 with acetic acid. All acids and water used are redistilled from borodicate glass The ammonium hydroxide is dijtilled from reagent grade and absorbed in redistilled water in borosilicate glass bottles. The buffer solutions are treated with tcarbate and extracted with chloroform before use. The beakers are soaked 24 hours in dilute ammoniated dithizone solution and rinsed twice with boiling 0.1N HC1. The strips of filter paper are eluted wkth 0.3N HCl for 12 hours by ascending chromatography. Procedure. T o 200 grams of milk in a 250-ml. beaker, add 10 ml. of 6 N HCl. The niilk is evaporated to dryness on the water bath and ashed slowly, preferably overnight, at 450' t o 500" C. Concentrated HNOa (8 ml.) is added to the gray ash and the sample reduced to dryness on a hot
Table 1.
Range of Concentration
Slo e O f
EXPERIMENTAL
Reagents. The ter*t-carbate is prepared by the method outlined by Gleu and Schwab ( 1 ) . Reagent grade carbon disulfice and Eastman P-1332 pyrrolidine are reacted in ethanol solvent under nitrogen gas. After pre-
Analytical line Zn 2771
Fe 2723.6 Mn 2605.7 MO 3158.2
standRange of standard ard
curve, %
curve
0.51 -2.03 0.0225 -0.09 0.0018 -0.0072 0.00375-0.015
41O 45" 45" 35"
plate and finally in the furnace for 1 hou a t 500" C. The resulting white ash is dissolved in 8 ml. of 6iV HC1 and digested on a hot plate for 15 minutes to assure conversion of pyrophosphates to phosphates. The clear solution is diluted to 40 ml. with water. The extraction procedure is essentially the same as that described by Scharrer and Jude1 ( 3 ) . 5-Sulfosalicylic acid (30 ml ) and 2 ml. of sodium acetate solution are added to each solution of milk ash. The p H i i adjuated to 3.8 with ammonium hydroxide and diluted to 120 ml. with water. The solution is heated to approximately 70" C. on a hot plate and transferred immediately to a 250-ml. globeshaped separatory funnel containing 10 ml. of the tert-carbate solution. The mixture is shaken vigorously for 30 seconds and cooled to room temperature. Chloroform (5 ml.) is added and the funnel shaken 2 minutes. The chloroform layer is transferred to a 10ml. round-bottomed beaker. Stray drops are collected by adding 4 ml. more rhloroform. This is also drained into the 10-ml. beaker. A strip of Whatman S o . 40 filter paper, 0 7 5 in. wide, 18 in. long, is suspended above the 10-ml. beaker and the end dipped into the solution. The paper strip is enclosed in an open glass tube 1.25 inches in diameter and 10 inches long. The solution travels up the paper several inches and the chloroform evaporates leaving the excess reagent and metal complexes adhering to the paper. The water solution is diluted to 200 ml. and extracted in the same way twice more. Each time, prior to extraction, 5 drops of 6 N HCl are added. The chloroform extracts are collected in a 25-nil beaker, the volume reduced a t room t m p e m t u r e by evaporation and then added to the 10-ml. beaker and abborbetl on the paper strip. The final pH of the water solution is approximately four. VOL. 35, NO. 12, NOVEMBER 1963
1957
~
/
~
