Sartori The War Gases Chemistry and analysis

266 SULPHUR COMPOUNDS

Methyl fluorosulphonate was obtained by Meyer i in 1932 by the action of fluorosulphonic acid on dimethyl ether :

LABORATORY PREPARATION *•

10 ml. fluorosulphonic acid are placed in a wash-bottle and a current of dry dimethyl ether, obtained by heating 1-3 parts methanol with 2 parts concentrated sulphuric acid to 140° C. is passed in. The methyl ether is absorbed and reacts immediately. For safety, a second wash-bottle should be inserted containing a

/OCH3

SO/ XC1

Methyl Chlorosulphonate was employed by the Germans both alone, and in admixture with dimethyl sulphate (75 parts dimethyl sulphate and 25 parts methyl Chlorosulphonate) under the name of " C-Stoff."

PREPARATION

The usual method of preparing this war gas is by the action of methyl alcohol on sulphuryl chloride x :

65 gm. sulphuryl chloride are placed in a flask of 150-200 ml., which is fitted with a dropping funnel and a reflux condenser connected at its upper end by a tube to a flask filled with water. The function of the water in the flask is to trap the hydrochloric acid which is evolved in the reaction. 15 gm. methyl alcohol (preferably dried) are allowed to drop in slowly from the tapfunnel. During this addition the reaction mixture is agitated continuously and the flask is cooled externally with ice. When all the alcohol has been added, the flask is allowed to stand for 2-3 hours and then heated to 50° to 60° C. on the water-bath, until all the hydrochloric acid has been evolved. The liquid product is then placed in a separatory funnel, washed rapidly with iced water and the heavier layer separated and distilled in vacua, the fraction boiling between 38° and 45° C. at 16 mm. pressure being collected.

PHYSICAL AND CHEMICAL PROPERTIES

It is a colourless liquid with a pungent odour and boils at ordinary pressure at 133° to 135° C. with decomposition. At 16 mm. pressure it distils unaltered at 42° C. It melts at — 70°C. and has a S.G. at 15° C. of 1-492, while its vapour density is 4-5 (air = i). The volatility at 20°C.is 60,000 mgm. per cu. m. It is immiscible with sulphuric acid,2 but miscible with carbon tetrachloride, chloroform and ethyl alcohol. It is insoluble in water, which hydrolyses it according to the equation :

and dimethyl sulphate, it does not split off its alkyl group on hydrolysis, but only the chlorine atom.

If the water is in excess, however, even the methyl sulphuric acid which is formed is decomposed into hydrochloric acid and methyl alcohol.3

1 BEHRKND, /. prtikt. Chem., 1877, [2] 15, 32.

" R. LEVAILLANT and L. SIMON, Compt. rend., 1919, 169, 140. 8 L. GUYOT and L. SIMON, Compt. rend., 1920, 170, 326.

2 mgm. per cu. m. of air (Miiller). The limit of insupportability according to Lindemann is 30-40 mgm. per cu. m. Mortalityproduct : 2,000 (Miiller).

This compound was used by the French, at the suggestion of Grignard, towards the end of 1915, because of its irritating action on the skin. It was also employed mixed with bromoacetone.

PREPARATION

It is generally prepared by the reaction of ethylene with chlorosulphonic acid in the cold 2 :

It may also be obtained by the action of fuming sulphuric acid on ethyl chloroformate.3

PHYSICAL AND CHEMICAL PROPERTIES

Ethyl chlorosulphonate is a colourless, oily liquid fuming in damp air and having a pungent odour. It boils at ordinary pressure at 152° to 153° C. and at 100 mm. pressure at 93°to 95°C.

It is insoluble in water and is readily decomposed by cold water

That is to say, it gives up the chlorine atom and not the alkyl

1 R. LEVAILLANT, Compt. rend., 1928, 187, 234. * MULLKR, Ber., 1873, 6, 228.

8 WILM, Ber., 1873, 6, 505.

270 SULPHUR COMPOUNDS

then distilled ; the distillate is tested for methyl alcohol and the residue for sulphuric acid.

QUANTITATIVE DETERMINATION

The quantitative determination of the sulphuric acid derivatives may be carried out as described in the paragraphs above dealing with their qualitative analysis : by decomposing the sample by warming with water or alkaline solutions and then determining the sulphuric and hydrochloric acids quantitatively.

Determination of Chlorosulphonic Acid. About i gm. of the sample is introduced into a small glass bulb which is then sealed in the flame and weighed accurately. This bulb is then placed in a tall glass cylinder of about 150 ml. capacity, containing about 100 ml. water. The cylinder is stoppered tightly and shaken violently so as to break the bulb, and then allowed to stand until the cloud which first forms in the cylinder completely disappears. The contents are then transferred to a 500 ml. flask and made up to volume. 200 ml. of the solution are then titrated with a decinormal sodium hydroxide solution, to the methylorange end-point, so as to obtain the total hydrochloric and sulphuric acid content. In another 200 ml. the hydrochloric acid is titrated with a decinormal solution of silver nitrate in presence of a few drops of potassium chromate solution, after addition of excess of pure calcium carbonate.

Calculation : If a gm. sample were taken and b ml. N/io sodium hydroxide and c ml. N/io silver nitrate were employed, then

Determination of Sulphuryl Chloride.^- A simple method of determining this substance is based on its quantitative decomposition into chlorine and sulphur dioxide when it is passed through a tube heated to dull-redness (see p. 259). Then on determining the chlorine and the sulphur dioxide by one of the ordinary methods, the amount of sulphuryl chloride present in the sample may be deduced.

1 Private communication from Dr. Rusberg (LUNGE-BERL, Chem. Tec/in.

Untersuchungsmethoden, yth edition, 1921, 877).

CHAPTER XV

ARSENIC COMPOUNDS

TOWARDS the end of the war of 1914-18, the attention of chemists searching for new war gases returned to the arsenic compounds which had already frequently been considered, on account of their great toxicity. Only a few had actually been employed, however, for their physical properties rendered them unsuitable in general. Thus all the inorganic compounds were discarded, excepting hydrogen arsenide,1 which was tested at the commencement, but was also abandoned because of its instability 2 and rapid diffusion 3 and arsenic trichloride, which had only a limited employment and that solely as solvent for the war gases (phosgene, hydrocyanic acid, etc.).4

A very large number of potential war gases was found amongst the organic derivatives however. The superiority of the organic arsenicals over the inorganic compounds is attributed to the fact that the former are, in general, soluble in the lipoids and dissolve preferentially in lecithin and cephalin, while the inorganic compounds are rapidly eliminated via the kidneys and the mucus.5

From the results of the researches carried out on the organic arsenic compounds, it is possible to divide these into the following groups :

Of these, the aromatic arsines were very largely used during the war, especially diphenyl chloroarsine. The aggressive action

271

272 ARSENIC COMPOUNDS

described previously, is provoked by finely divided solid particles, which on liberation in the air form true smokes and are known as the "toxic smokes." Phenyl dichloroarsine is an exception, not being a smoke.

Most of the aliphatic and aromatic arsines employed during the war of 1914-18 were substances which had been known for some time. The only new substances are the chlorovinyl arsines and phenarsazine chloride, of whose practical efficiency somewhat conflicting opinions are still held.

The fact that during the war only the compounds mentioned above were actually used does not indicate that they were superior to others which have been prepared and studied. Nevertheless, it is probable that preference will be given to those substances whose range of application is known, without using compounds of uncertain scope.

(A) ALIPHATIC ARSINES

The aliphatic arsines are substances which are generally liquid and oily, have a not unpleasant odour, are somewhat miscible with water, but are all more or less rapidly hydrolysed as follows :

These substances, though more powerfully toxic than the aromatic arsines, are of minor importance because of their rapid diffusion in the air without forming aerosols.

Even the chlorovinyl arsines, although they are easily prepared, do not seem to be sufficiently aggressive in their action to replace the aromatic arsines. According to several authorities,1 experiments on the methods of military application of the chlorovinyl arsines have been abandoned even in America.

Of the aliphatic arsines, only ethyl dichloroarsine has been widely employed as a war gas and is considered as the typical substance for use in projectiles. Methyl dichloroarsine is classed by some German authors 2 as a substance which was studied in the post-war period, but according to an American authority it was actually employed by the Allies towards the end of the war, though only in small quantity.3

Since the war, various other compounds of similar properties and method of preparation have been prepared and studied.

1 HANSLIAN, Der Chemische Krieg, Berlin, 1927, 62.