596 DR E. A. LETTS ON THE 
I IL Calculated for 
: S(CH,COO),Pb . 
Lead, . 5 : : 57D 578 58°53 
Sulphur, : : : 8:7 8:7 9:0 
Carbon, . é ; b 135 bee 135 
Hydrogen, . : ; 1:2 ee shal. 
Oxygen, : : ‘ Get eo Lot. 
100:0 100-0 
Silver Salt of B2. 
‘3065 gave ‘179 silver . 584 per cent. 
0d ot elon bs, 58°5 
S (CH,—COOAg), requires 59°3 
» 
> 
These results clearly indicate the nature of the decomposition which the 
thetine salt suffers when heated. Two molecules of the hydrobromate 
are resolved into a molecule of thiodiglycollic acid, a molecule of bromide of 
methyl, and a molecule of the sulphine compound. 

CH, 
| 
CH,—S—Br 
Mek : CH,—COOH CH, 
~ ¢H,—COOH 
| Bei + Br-S—CH, 4 CH.Be 
ee gee. eh eeinart CH, 
CH, page Br 
CH, - ok 
~CH, oe 
Thiodiglycollic acid is the true sulphur analogue of triglycol-amidie acid, 
and the action of heat on the hydrobromate of dimethyl-thetine (which we may 
regard as the action of heat on sulphide of methyl and bromacetic acid) may be 
strictly compared with the action of heat on ammonia and bromacetic acid. In 
both cases the final product is a body resulting from the replacement of the 
radicals bound to the sulphur and nitrogen respectively (methyl and hydrogen) 
by the radical glycolyl.* 
* The above experiments were made before those described on pp. 612—617 on the action of hydro- 
carbon sulphides on bromacetic acid, which go still further to establish an analogy between the action 
of ammonia on bromacetic acid and the action of hydrocarbon sulphides generally, on the same sub- 
stance, and also before the experiments on the action of sulphide of methyl on iodacetic ethyl ether, 
which led to the discovery of methyl-thioglycollic acid. It is quite possible that the latter substance 
is formed along with thiodiglycollic acid when hydrobromate of dimethyl-thetine is heated, and that 
in the above experiments it remained in the residue of the non-volatile products after the latter had 
been extracted with ether (product A). At the time the experiments were made however, this 

