ously for a few minutes, so that the peroxide solution will completely absorb the gaseous fumes which have evolved from the reaction. Distilled water, 300 ml., is introduced into the flask and the mixture is shaken for a minute longer. The spiral is removed and washed with a few milliliters of distilled water, and the washings are caught in the flask. The flask is placed on a hot plate and boiled until the volume of solution has been reduced t o 50 ml. It is then cooled under a stream of cold tap water, 2 drops of methyl red are added, and the solution of sulfuric acid is titrated with 0.02N sodium hydroxide solution to a yellow end point. For the liquid samples a blank determination on the gelatin capsule was run, by merely omitting the sample. Small capsules obtained from a local drug store required 1.10 ml. of 0.02N sodium hydroxide. CALCULATION I (Volumetric) M1. of NaOH X N X 16.03 X 100 Weight of sample
= %S
PROCEDURE I1
This procedure is employed for determining organic sulfur in compounds containing nitrogen, halides, phosphorus, or metals. The sample is treated as in Procedure I to the point where it is reduced t o 50 ml. It is then washed into a 250-ml. beaker, 3 ml. of 0.1N hydrochloric acid are added, and, while the sample is still hot, 2 to 3 ml. of 10% barium chloride solution are added dropwise with continuous stirring. The beaker is covered with a watch glass and permitted to stand undisturbed for 2 hours. The precipitate of barium sulfate which has formed is then transferred to a previously tared and dried Gooch crucible. The precipitate is washed six times with 25-ml. portions of dilute hydrochloric acid (1 t o 300) solution, dried in a n
oven a t 110” C. to constant weight, cooled in a desiccator, and weighed on a micro or semimicro analytical balance. CALCULATION I1 (Gravimetric) Weight of BaSOl X 0.1374 X 100 Weight of sample DISCUSSION
OF
-
%S
This makes t h e method very adaptable t o the requirements of industrial laboratories. Methods for the determination of phosphorus are being investigated and show promise. Work on other elements is also being considered.
RESULTS
The procedure as described provides a simple, economical, rapid, safe, and accurate method for determination of sulfur in organic compounds. A number of organic sulfur compounds prepared and purified in the organic department of this laboratory and several commercially available pure compounds were analyzed by Procedures I and 11. The results (Table I) compare favorably with those b y the Parr combustion method. The technique as described was found to be perfectly safe and eliminated the hazard of using strong oxidizing agents, such as sodium peroxide, for the Parr method and fuming nitric acid for the Carius method. The procedure is especially convenient for working with compounds of unknown reactivity. Explosions which have occurred using sodium peroxide have been eliminated. On a costwise basis, the equipment used represents a small fraction of the purchase price of combustion bombs and Carius combustion furnaces. These analyses can be run in any laboratory with a minimum cost and time. The method has general applicability and can be used for almost any type of organic matter containing sulfur, including compounds containing as high as 50% sulfur. After combustion of the organic matter in the flask, the sulfur can be determined by any method for elementary determination of sulfur.
LITERATURE CITED
(1) Carius, L., Ann. 116, l(1860). (2) Carius, L., Ber. 3,697 (1870). (3) Hallett, L. T., Knipers, J. IT., IND.Em. CHEY., ANAL. ED. 13, 357 (1940). (4) Horeisrhys, K., Buhler, F., Mikiochemie ver. M x r o c h i m . Acta 33, 231 (1947). (5) Kuck. J. A.. Griffel. M.. IND.EXG. CHEM.,ANAL. ED: 12,’125 (1940). (6) hlikl, O., Pech. J., Chem. listy 46,
382 (1952). (7) Kiederl, J. B., Xiederl, V., “Micromethods of Quantitative Organic Analysis,” 2nd ed., p. 182, Wiley, New York, 1942. (8) Parr Instrument Co., Moline, Ill., Parr Manual 12, 1950. (9) Pell, E. W., Clark, R. H., Wagner, E. C., IND.ENG. CHEM., AKAL. ED. 15, 149 (1943). (10) Pregl, F., 4th English ed., p. 101, Blakiston. Philadehhia. 1948. (11) Schoniger, W., Miklcrochim. Acta 1955, 123. (12) Ibid., 1956,869. (13) Scott, T. W., “Standard Methods for Chemical Analysis,” 5th ed., ed. by N. H. Furman, Vol. 11, p. 1643, Van Kostrand, New York, 1929.
(14) Steyermark, A., “Quantitative Organic Microanalysis,” p. 156,
Blakiston, New York, 1951. (15) Steyermark, A., Barr, E. A , , Littman, B., ANAL.CHEM.20,587 (1948). (16) Warshowsky, B., Shook, T. S., Schantz, E. J., Ibid., 26, 1051 (1954).
RECEIVEDfor review June 27, 1957 Accepted November 13, 1957.
Field Sampling and Analysis of Micro Quantities of Sesquimustard in Presence of Mustard ABRAHAM KOBLIN U. S. Army Chemical Warfare laboratories, Army Chemical Center, Md.
An analytical technique has been developed whereby mustard and sesquimustard can b e determined quantitatively in the presence of each other. Both compounds are analyzed by two different techniques and from simultaneous equations derived from the slopes of the colorimeter calibration curves; the quantity of each can b e estimated. The adoption of this technique has reduced the complexity
430
ANALYTICAL CHEMISTRY
of field sampling techniques of these compounds and has provided means of obtaining more reliable data, especially when tests are conducted a t lower temperatures.
A
arose to determine microquantities of sesquimustard in the presence of equal or large quantities of mustard. Sesquimustard, bis(2-chloKEED
roethylmercapt0)-ethane, has a melting point of 56” C. and is a white crystalline solid at room temperature. Mustard gas, on the other hand, has a melting point of 14’ C. and is a waterwhite liquid at room temperature when pure. Both of these compounds are strong vesicants. From laboratory and pre-exploratory field studies, it was found that mustard was one of the primary decomposition
products of sesquimustard and was collected on sampling filter mats together with sesquimustard. It required u p to 30 minutes to free the filter mat from mustard at low temperatures, so a n aeration process proved fruitless. At the time, there were no specific tests to distinguish between these two compounds. A technique was sought whereby two analytical schemes, common to mustard and sesquimustard, could be utilized, and with simultaneous equations derived from the calibration curves, could estimate the quantity of each compound. Both compounds give colored reaction products when allowed to alkylate 4( p - nitrobenzy1)pyridine followed by the addition of a base (piperidine) as shown by the following general equations: R-SCHZCH,Cl
+
c1piperidine OH -
Purple color Both compounds are attacked at the sulfur linkage b y chloramine-T or bromine t o give sulfoxides. The sesquimustard having two sulfurs requires twice the quantity as does mustard. The following equations exemplify this reaction: CICHzCH~SCH~CHzCl bromine Mustard CICHzCH&CH2CH2Cl
d Sulfoxide ClCHzCH2SCHZCH2SCH2CH&lbromine Sesquimustard ClCHzCHzSCH&H?SCHZCH&l 0 "
11
0
Disulfoxide
d technique devised by Geckel (2) at ilrmy Chemical Center utilized the bromine oxidation reaction and the alkylation of 4-(p-nitrobenzyl)pyridine to determine mixtures of sesquimustard and mustard. Simultaneous equations were used in this instance for estimating the quantity of each. The excess chloramine-T was determined colorimetrically by the addition and oxidation of a tolidine reagent. The disadvantage of this method mas in the high colorimeter reading obtained when lo^ concentrations of either mustard or sesquimustard were present.
Spot-test techniques on filter paper reported b y National Defense Research Council (NDRC) (4) and Hanker and associates (3) nhich utilized benzidinecopper acetate reagent and cobalt reagent, did not really lend themselves to field sampling procedures. Pursuing the N D R C report further, it was found t h a t when o-dianisidine was substituted for benzidine, and after the addition of a copper acetate solution, a strong red color was produced with sesquimustard in ethyl alcohol after the addition of strong acid. This reaction can be explained b y the work of Tschugaeff (6-9), who investigated the coordination of dithioethers with copper and nickel, and Copley. Foster, and Bailer ( I ) , Randles (6),and Hanker and others (3) on the theoretical treatment of the stabilization of valency states by coordination ITith amines. I n the reaction between sesquimustard and cupric ion, a coordination complex is formed. The complex having copper in the cupric state is a greater oxidizing agent than the cupric ion alone. Consequently, the dianisidine can be readily oxidized to a characteristic dye color which is red at low p H values. The application of these theories to mustard and sesquimustard are shown in the following expressions: Tschugaeff (6-9) RS( CHgCH2)nSR RSCHzCHzSR RSCHzCHzSR CU
+
where n
=
++
\
/
cu++
0, 1,3,or 5 Crystalline
compound; no complex formation as evidenced by no formation of precipitate.
Sesquimustard ClCHzCHzSCHzCHzSCHzCHzCl CU ClCHzCHZSCHzCH&3CHzCHzCl
+
\
++
/
Cut+ Copley, Foster, and Bailer ( 1 ) ClCHzCH?SCHzCHzSCH2CH$.21+ CU ClCHzCH?SCH&HzSCHzCHzCl 'CU+/ Cupric
+ ++
ClCH,CHzSCHzCHzSCHzCHzCl
\
/
Cu++
Cupric o-Dianisidine+ Ph 1-2 ClCHzCHzSCHzCHzSCHzCH,Cl
/
\
cu Cuprous
+ red color
+
EXPERIMENTAL
This reaction was further investigated to determine its sensitivity and repro-
-f
200-
.
I
3
I/// 0
50
D
IO0 150 Y!CROGRAMS/NL. OF
200
250
SOLUTION
Figure 1. Calibration curves for sesquimustard and mustard by o-dianisi4-(pnitrobenzyl)pyridine dine and methods A.
E. C.
D.
Mustard by 4-(p-nitrobenzyl)pyridine method Sesquimustard b y 4-(p-nitrobenzyl) pyridine method Sesquimustard b y o-dianisidine method Mustard b y o-dianisidine method
ducibility, and the extent to which mustard enters into this reaction. Reagent Solutions.
o-Dianisidine,
0.1% solution in absolute ethyl alco-
hol. Copper acetate, O.lyoaqueous solu-. tion containing 0.001 ml. of glacial acetic acid per 1 ml. of solution. Sulfuric acid, 18-Y. Sesquimustard, assayed 99% by Chemical Research Division, U. S. Army Chemical Warfare Laboratories. Mustard gas, assayed 99.9% by Chemical Research Division, C . S. Army Chemical Warfare Laboratories (synthesized by thiodiglycol method). Apparatus and Equipment. KlettSummerson colorimeter with No. 54 filter. Klett tubes. Stirring rods with glass foot. Pipet and volumetric flasks for aliquoting. Procedure. T o a preweighed volumetric flask containing approximately 10 ml. of absolute ethyl alcohol, approximately 0.2 gram of sesquimustard was added and the flask weighed to the nearest 0.1 mg. Dilutions of this stock solution were made with concentrations of sesquimustard ranging from 20 t o 100 y per ml. O-DIANISIDIXE TEST. One-milliliter aliquots of these standards were pipetted into clean dry Klett tubes and 1 ml. of dianisidine reagent was added to each. At 30-second intervals, 3 ml. of copper acetate reagent were added t o each tube and the contents stirred well. After the first sample had stood for 10 minutes, 3 ml. of sulfuric acid reagent were added to each tube a t 30-second intervals, the solution again was stirred well, and the color read. Reagent blanks were determined using all reagents substituting absolute ethyl alcohol for the standard sesquimustard solutions. The blank reading was subtracted from the gross readings giving net colorimeter readings. VOL. 30, NO. 3, MARCH 1 9 5 8
431
The net colorimetric readings plotted against the concentration of sesquimustard per milliliter on coordinate paper resulted in a straight line showing that Beer's law was readily satisfied, The same procedure was followed using standard solution of mustard in ethyl alcohol t o determine the extent t o which mustard entered into this reaction. These data are plotted in Figure 1. #?(P-NITROBENZYL)PYRIDINE
Standard solutions of sesquimustard and mustard in ethyl alcohol were prepared and analyzed by this procedure. The data obtained are plotted in Figure 1. From the slopes of the four curves, equations were established and expressions for sesquimustard and mustard were derived as follows:
W S = 0.714 RA - 0.00539 RE W M = 0.253 RB - 0.671 RA where = y
of sesquimustard per milliliter of solution
Net Colorimeter Quantity Reading Recovered, Y Units Y RE S 11 RA 21 32 28 212 19 35 48 32 44 314 30 50 80 54 76 524 51 82 71 640 114 2800" 66 642 a Dilution, 1 to 10. RA = colorimeter reading by coppero-dianisidine. RB = colorimeter reading by 4-(p-nitrobenzy1)pyridine. Quantity Sought,
TEST.
An alkylation method of analysis ( 2 ) was modified slightly so that ethyl alcohol could be used as the solvent in place of diethyl phthalate. Instead of heating the mustard and sesquimustard with 4(pnitrobenzyl)pyridine reagent for 5 minutes at 100" C., the bath temperature was lowered t o 70' C., and the heating time increased to 15 minutes. These conditions gave reproducible results.
Ws
Table 1. Recovery of Sesquimustard (S) and Mustard (M) from Mixtures
W M= y of mustard per milliliter of solution RA = net colorimeter scale units obtained by copper-o-dianisidine method RB = net colorimeter scale units obtained by 4-(p-nitrobenzy1)pyridine method Several mivtures of mustard and sesquimustard were prepared and analyzed b y the methods described above. Recoveries greater than 90% with an accuracy to &3% in the 75-7 range were obtained. The data are shown in Table I. I n handling field samples, the filter mats having sesquimustard and mustard on the collection surface, were added t o a given volume of alcohol.
Aliquots were taken from this extract and analyzed b y the two methods, and the quantity of each compound was calculated by substituting the colorimeter readings in the equations. LITERATURE CITED
(1) Copley hi. J., Foster, L. S., Bailer, J. d., Jr., Chem. Revs. 30, 227
(1942). (2) Geckel,' P. T., TCR 80, Chemical Corps, Chemical and Radiological Laboratories, Army Chemical Center, Md., "Colorimetric Method for Estimation of Mustard and Sesqui in Mixtures of Mustard and Sesqui," February 1951. (3) Hanker, J. S., Master, Irwin, Mattison, L. E., Witten, Benjamin, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., February 1956. (4) National Defense Research Council, Division 9, OSRD 4288, Sept. 30, 1944. ( 5 ) Randles, J. E. B., J. Chem. SOC. 1941,802. (6) Tschugaeff, L., Ber. 41, 2222 (1908). (7) Tschugaeff, L., Compt. rend. 154, 33 (1912). (8) Tschugaeff, L., Kobejanski, A., 2. anoru. Chem. 83. 8 (1913). (9) Tschugaeff, L., Subbotin, W., Ber. 43, 1200 (1910). '
RECEIVEDfor review January 5, 1957. Accepted Xovember 15, 1957. Division of Analytical Chemistry, 130th Meeting, ACS, Atlantic City, N . J., September 1956.
Photometric Determination of Zinc Oxide in Rubber Products Absorptiometric and Turbidimetric Methods Using Sodium Diethyl Dithiocarbamate K. E.
KRESS
The Firestone Tire & Rubber Co., Akron,
b Zinc is precipitated from a weakly alkaline medium as zinc diethyl dithiocarbamate, which is then extracted with ether. The absorbance of the complex in ether solution may b e measured a t 262, 280, or 295 mp. Alternatively, the absorbance of a colloidal aqueous suspension of the precipitate may b e measured a t 448 mp. Interference from other cations is uncommon but is detectable when it occurs, and can b e corrected for b y an absorbance difference method. W e t ashing with perchloric acid on a micro scale eliminates errors observed 432
ANALYTICAL CHEMISTRY
Ohio with conventional dry ashing of some rubber products.
Z
INC OXIDE added to activate vulcani-
zation is the ,most important isorganic material in nearly every type of rubber product. The ASTM standard volumetric procedure for zinc oxide determination in rubber products calls for ferrocyanide titration with uranyl acet a t e as a n external indicator (1). This method has proved less satisfactory than titrations with an internal indicator such
as diphenylbenzidine ($0). However, the slow rate of titration required with diphenylbenzidine and the difficulty in determining the exact end point have at times resulted in considerable error. The need for removal of interfering iron and limitation of the method to samples preferably containing in excess of 100 mg. of zinc oxide for accurate results complicates the analysis. Other volumetric methods such as iodometric titration and precipitation as the oxalate have been proposed, but as far as is known, they have not been applied to analysis of rubber products.
