616 DR E. A. LETTS ON THE 
small distilling flask heated in an oil-bath and connected with a LiEzica’s 
condenser. The oil-bath was heated to 150-170". } 
The mixture soon fused, grew quite brown, then black; a heavy liquid 
passed over very gradually, and hydrobromic acid was disengaged in large 
quantity. 
The experiment was stopped when the action appeared to have ceased, which 
only occurred after two or three hours. The volatile product which passed 
over was not quite homogeneous, but consisted of two distinct liquids,—one of 
which was present in large quantity, and was very heavy; the other floated as 
a distinct layer, and amounted only to a very small quantity. Both together 
weighed 6 grms. 
The liquid present in largest quantity was bromide of ethylene. This 
was proved by its odour, high specific gravity, and by the fact that when mixed 
with alcoholic sulphide of potassium the mixture grew warm and the charac- 
teristic amorphous sulphide of ethylene was precipitated,—the aqueous wash- 
ings from which yielded a copious yellow precipitate when treated with nitrate 
of silver, which was easily identified as bromide of silver. 
The non-volatile products of the reaction solidified on cooling to a crystalline 
mass. This was treated with water, and yielded a claret-coloured solution, 
together with a considerable quantity of black unsoluble matter, which appeared 
to consist of charred products. 
The colour of the solution was much altered by an alkali—becoming brown ; 
but on the addition of acid to the alkaline solution the original colour was 
restored. 
The whole of the solution was neutralised with baryta and evaporated 
down. During the evaporation brownish flakes were precipitated, and the 
colour of the solution became much lighter. As soon as the concentration 
was judged to be sufficient, it was allowed to cool and remain at rest for some 
time, when abundance of crystals having the appearance of thiodiglycollate of 
barium separated 6ut. That these consisted of the thiodiglycollate was proved 
by a barium determination (36°6 per cent. of barium was found instead of 
36°5 per cent., the theoretical quantity), and also by the production of the 
characteristic thiodiglycollate of lead, and a determination of lead in it (581 
per cent. of lead was found instead of 58:2). 
These results are sufficient to show that the action of sulphide of ethylene 
on bromacetic acid is of the same kind as the action of the sulphides of 
benzyl and allyl on bromacetic acid, and is, in fact, a case of double decom- 
position— 
C,H,S + 2(CH,CO,H)Br = C,H,Br, + S(CH,CO,H),. 
That an altogether different action, however, occurs at the same time was 

