ACTION OF HYDROCARBON SULPHIDES ON BROMACETIC ACID. 613 
of sulphide of benzyl and bromacetic acid might behave as such when heated, 
or at least yield similar products, viz., bromide of benzyl and thiodiglycollic 
acid, as I have shown that the hydrobromate of dimethyl-thetine very readily 
splits under the action of heat into bromide of methyl, sulphide of methyl, 
and thiodiglycollic acid. 
In order to ascertain whether this reaction really occurred, the mixture 
of solid and liquid products obtained by heating benzyl sulphide and 
bromacetic acid for some time, was repeatedly extracted with water. The 
residual oil had a pungent and irritating odour, which acted on the nostrils and 
eyes powerfully. It was distilled in a current of steam, separated from the 
water which accompanied it, and saponified with alcoholic potash solution. 
The mixture was then acidulated with nitric acid and yielded a copious 
precipitate with nitrate of silver, which was yellow, coagulated when shaken, 
and possessed the other properties of bromide of silver. 
The aqueous washings employed to extract the products of the action of 
heat on the sulphide of benzyl and bromacetic acid. were neutralised with 
caustic baryta solution, excess of baryta removed by a stream of carbonic 
anhydride, and the filtered solution evaporated and allowed to cool, when a 
barium salt separated out in characteristic radiating blunt needles. A deter- 
mination of barium and water in this salt showed that it consisted of thiodi- 
glycollate of barium— 
Calculated for 
it II. S(CH,COO),Ba, 5H,0. 
Water of Crystallisation, . . 24:00 24:0 
Barium, . 4 : 4 : 36°9 36°5 36°5 
The crystals which separated after some weeks from the mixture of benzyl 
sulphide and bromacetic acid, which was only just sufficiently heated to fuse 
the two substances, also behaved as thiodiglycollic acid, yielding the very 
characteristic barium salt and the equally characteristic lead salt. This lead 
salt is precipitated in an amorphous flocculent condition by the addition of ace- 
| tate of lead to solution of thiodiglycollic acid. On warming the mixture it 
dissolves, but is almost immediately replaced by a beautiful salt crystallising in 
glittering spangles. 
These results show that when sulphide of benzyl and bromacetic acid are 
mixed together they yield thiodiglycollic acid and bromide of benzyl—in other 
words, that double decomposition occurs between them, the bromine of brom- 
acetic acid becoming replaced by sulphur, and the sulphur of sulphide of benzyl 
by bromine. Thus— 
2(CH,—CO,H)Br + (C,H,).S = 2C,H,Br + S(CH,CO,H),. 
| 
This reaction occurs rapidly when the two substances are heated together— 
slowly when they remain in contact at ordinary temperatures. 

