DIMETHYL-THETINE AND ITS DERIVATIVES. 581 
and might decompose when treated with water into hydriodic acid and the 
hydrated base. The presence of a small quantity of the latter in the recrystal- 
lised product would account for the slight deficiency of iodine. 
Polyiodide of Dimethyl-Thetine.—The beautiful crystalline salt resembling 
permanganate of potash in appearance,—which was obtained by the sponta- 
neous decomposition of the hydriodate, or by allowing dilute hydriodic acid to 
remain for a long time in contact with the base,—is a polyiodide of dimethyl- 
thetine. It forms well-defined crystals, which are insoluble in water, but 
soluble in alcohol and ether. Warmed with water they fuse to oily drops, 
which on cooling do not readily solidify. 
The analysis of the salt was effected by dissolving it in aleohol and adding 
standard hyposulphite solution; as soon as it was decolorised, the total 
iodine was determined by precipitation as iodide of silver. 
The numbers obtained agree with the formula— 
(CAELSO,) | Hil - 
Calculated in 100. Obtained. 
(SSS 
Free Iodine, . : : 50°6 50:7 50°5 50-4 
Total Iodine, . s ; 759 75:4 Si 
Other polyiodides were obtained by adding iodine to a solution of the base 
in hydriodic acid. These were beautiful salts with a greenish metallic lustre. 
As they were probably mixtures, they were not examined more closely. 
Sulphate of Dimethyl-Thetine.-—This salt is obtained by the action of sul- 
phate of silver on the hydrobromate. 
The hydrobromate is dissolved in-water, rather more than the equivalent 
quantity of sulphate of silver added, and the mixture warmed in a water bath 
and well stirred. From time to time a little of the solution is removed and 
tested with sulphate of silver, and when this ceases to be affected, the whole is 
thrown on a filter, and the solution, after removing the small quantity of dis- 
solved sulphate of silver by addition of hydrochloric acid, concentrated either 
Over a water bath or in vacuo over sulphuric acid. When syrupy the solution 
solidifies to a crystalline mass. 
Sulphate of dimethyl-thetine is a colourless crystalline body, and is per- 
haps the least soluble of all the dimethyl-thetine salts, and is not deliquescent. 
Nevertheless, its aqueous solution may be concentrated till of syrupy con- 
sistence, and frequently remains thus without crystallising. The salt is very 
slightly soluble in alcohol, and is readily precipitated by that reagent from its 
concentrated aqueous solution. It has a pleasant sour taste, and its solution 
reddens litmus paper. 
