Detection of War Gases PAUL F . FENTON liniversity of Vermont, Burlington, Vermont
N TWO previous papers', methods for the field detectlon of some war gases were described. The procedure involved adsorbing the gas on silica gel contained in a glass tube and carrying out one or more chemical reactions in the tube to develop a distinct and characteristic color. While these methods were reasonably sensitive, reliable, and simple of execution, one serious technical difficulty remained: a new tube had to be used for each test carried out. This becomes a serious problem under field conditions where the nature of the gas is unknown. It means that the individual carrying out the test must take a sample of the gas from the scene of the incident and go to one side to perform the test. If the test results are negative, he must return and obtain additional samples and perfom additional tests until identification is complete. Since mifiures are likely to be encountered, the analyst must probably execute almost every test for which he is equipped. As an alternative to this time-consuming procedure, he could obtain all necessary samples a t one time. However, since it is likely that he would be wearing protective clothing, this process is not simple. To solve this problem the following procedure has been devised and tested. It employs in principle the same chemical reactions described in the earlier papers.', Contamiuated air is aspirated through a silicagel tube. The gel is then poured into one of the depressions of a spot plate and thoroughly mixed. With a nmow-tipped spatula small portions of gel are transferred to other depressions and tests for specific gases carried out on the several portions. It is advisable to aspirate more air for this procedure than if only a single test is run directly on the silica gel within the tube. The following specific ' tests have been used successfully in this laboratory: 1. Adamsite: Transfer the distal cotton plug from the silica gel tube to the spot plate. Add several drops of alcohol and agitate with a stirring rod or other suitable device. Then add a drop of N/10 potassium dichromate acidified with sulfuric acid. A greenish blue color develops. Jacobsa has pointed out that the detection of Adamsite can be based upon the presence of diphenylamine as contaminant. The above test has been tried only on diphenylamine since no Adamsite could be obtained for use. 2. Chlorine: To a small portion of silica gel add a fraction of a drop of potassium bromide-fluorescein
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I FENTOA. "Vapor detector tubes and detector kit for some chemical agents used in gas warfare," J. CHEM.EDUC.,20, 5 6 P 5
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2 FENTON, "Detection of war gases. Hydroc)ianic acid and rhloropicrin," ibid., 21.92 (1944). a JACOBS, "War Gases." Interscience Publishers. Inc.. Xew York. 1942, p. 129
reagent. If chlorine is adsorbed on the silica gel a red color develops. This test should be done before all others since the chlorine seems to be lost rapidly after the silica gel has been removed from the tube. The reagent is prepared by dissplving 0.2 g. fluorescein, 30 g. potassium bromide, 2 g. potassium hydroxide, and 2 g. sodium carbonate in 100 ml. of water. 3. Leuride: On the spot plate mix one drop of Ilosvay reagent with two drops of 20 per cent potassium hydroxide and moisten a portion of silica gel with a fraction of a drop of this akalinized Ilosvay reagent. If Lewisite was adsorbed on the gel, the characteristic purple will be obtained in spots since the gas is not equally adsorbed on each of the gel granules. It has been a source of some imtation that the Ilosvay reagent is so unstable. To overcome this difficulty the components of the reagent were dissolved individually: 3 g. copper sulfate, 3 g. ammonium chloride, 5 g. hydroxylamine hydrochloride, and 4 ml. of concentrated ammonium hydroxide, each in 25 ml. of water. At the time of the test one drop of each of these solutions is mixed to make the reagent, of which one drop is added to two drops of the alkali for the test. 4. Chlor'crin: As has been pointed out', %twotests are available for this gas. If to a small portion of silica gel (with chlorpicrin adsorbed) a fraction of a drop of dimethylaniline is added, an orange color develops. The second test depends on the presence of the nitro group in the gas. To a portion of silica gel add 5 drops of sodium alcoholate and touch a burning match to it. The burning of the alcohol supplies the heat necessary to bring about the decomposition of the chlorpicrin and the formation of sodium nitrite. The latter is identified by adding several drops of sulfanilamide reagent which produces a purple color. The sodium alcoholate is prepared by reacting 8 per cent sodium amalgam with alcohol. The sulfanilamide reagent is prepared by dissolving 0.2 g. sulfanilamide and 0.2 g. N-(1-naphthy1)ethylenediamine dihydrochloride in 20 ml. of concentrated hydrochloric acid. 5. Phosgene: To another portion of the silica gel add a drop of diphenylamine (10 per cent solution in alcohol) and a drop of dimethylaminobenzaldehyde (Pfanstiehl, 10 per cent solution in alcohol). If phosgene was adsorbed, a yellow color develops. Other substances such as hydrochloric acid will also give the reaction. 6 . Hydrogen cyanide: To a portion of the silica gel add several granules of ferrous sulfate and two drops of 20 per cent potassium hydroxide. Stir thoroughly to dissolve some of the ferrous sulfate. Add two drops of alcohol and ignite. Then add two drops of femc
489 chloride in hydrochloric acid (equal parts of 5 per cent ferric chloride and concentrated hydrochloric acid). Pmssian blue is formed if hydrogen cyanide was adsorbed on the silica gel. 7. Mustard: To a portion of silica gel add a few granules of the DB-3 silica gel issued by the Office of Civilian Defense to d i l l the detector tubes of the M-4 kit. Add a drop of alcohol, ignite, and then make alkaline with a drop of 20 per cent potassium hydroxide. If mustard is present, some of the gramles become blue. When this series of tests has been completed, it might be well to take one more sample of the gas in a silica gel
tube and carry out the specific test directly in the tube by the methods described previously.'. To this group of tests one more can be added, a test for chlorine. Simply introduce a drop of potassium bromide-fluorescein reagent into the silica gel tube thought to contain chlorine. A bright red color develops. This test has been described above as adapted to the spot plate technique. Whether the DB-3 silica gel can be used to replace the ordinary gel used in the spot plate technique remains to be tried by someone with an adequate supply of the DB-3 gel.
