576 PROFESSOR CRUM BROWN AND DRE. A. LETTS ON 
hydrate is continued until the boiling liquid ceases to dissolve it; the solution 
is then rapidly filtered ; as it cools the double salt separates in beautiful silvery 
scales, which may be purified from mother liquor by washing with a little cold 
water. 
The analysis of this salt shows that it is a compound of 2 molecules of 
bromide of lead with 1 molecule of dimethyl-thetine— 
CH, 
| 
C,H,SO, ,2PbBr, or Br—S—CH,—COOPbBr, PbBr,. 
: CH, 
Anta ag ER 
Carbon, : : : BT oF 56 
Hydrogen, . 3 ; 0-9 0-9 0-9 
Bromine, . : J 37:0 aT) 37°0 
Lead, : : , 48-4 485 48-4 
Its formation may be represented by the equation— 
4(C,H,BrSO,) + 2Pb(OH), = C,H,SO0,, 2PbBr, + 3(C,H,,SO,) + H,0. 
That hydrated dimethyl-thetine is produced along with the lead salt was 
proved by evaporating the mother liquors on a water bath, extracting the 
residue with alcohol, and adding to the alcoholic solution hydrochloric acid 
and chloride of platinum, which caused the precipitation of the orange-coloured 
chloro-platinate of dimethyl-thetine, the composition of which was verified by a 
platinum determination. The lead salt is very sparingly soluble in cold water, 
but dissolves to a considerable extent in boiling water, from which it may be 
recrystallised. p 
Action of Hydrobromate of Dimethyl-Thetine on Ethylate of Sodium, Oxide 
of Copper, Oxide of Mercury, and Ammonia.—The action of the hydrobromate 
on ethylate of sodium appears to vary with the conditions, and has not been 
thoroughly investigated. In one experiment, on boiling the hydrobromate for 
some time with ethylate of sodium dissolved in alcohol, the solution almost 
solidified to a crystalline mass. These crystals were with difficulty soluble 
in boiling alcohol. An estimation of the sodium which they contained gave 
14°6 per cent., whereas the compound C,H,SO,, 2NaBr requires 144 per cent. 
A bromine determination gave, however, too small a quantity for the above 
formula, viz., 36°8 per cent. instead of 49°0. In another experiment, 5 grms. of 
hydrobromate and 6 grms. of sodium * were separately dissolved in absolute 
alcohol, and the solutions mixed together, warmed, and filtered. The filtered 
* These quantities represent 1 molecule of the hydrobromate and 1 atom of sodium. 

