244 Dr. Thomas Thomson on [Oct. 



shining points interspersed, as if it consisted of minute 

 crystals. It has no sensible taste. Its sp. gr. is 3*168. 



At the temperature of 60°, 100 parts of water dissolve 

 0-021 of this salt ; and 100 parts of boiling water dissolve 

 0-088 of it. 



From the experiments on this salt, described in the 

 beginning of this paper, it appears that when it has been 

 dried in the open air, without artificial heat, it is a com- 

 pound of 1 atom racemic acid . . . 8*25 

 1 atom protoxide of lead . . 14- 

 4f atoms water 5*245 



27-495 

 But the greater part of this water is probably only mecha- 

 nically mixed ; for, when exposed to a heat not exceeding 

 100° there only remains IJ atoms water, which, therefore, 

 I am disposed to consider as the whole chemically combined 

 water which it contains. 



XVII. — RACEMATE OF TIN. 



When solutions of chloride of tin and racemate of soda 

 are mixed in atomic proportions a white curdy precipitate 

 falls, which may be washed, and dried on a filter. It is a 

 chalky looking powder, which reddens vegetable blues, 

 and has a slightly sweetish and acid taste. 



Its sp. gr. is 2-197. At the temperature of 100 water 

 dissolve 0*146 of this salt. The matter dissolved consisted 

 chiefly of racemic acid, though it contained likewise oxide 

 of tin. 100 boiling water dissolve 0*83 of the salt; and 

 this dissolved portion contains a greater excess of racemic 

 acid than the cold solution does, judging from its taste and 

 appearance. 



20 grs. of the salt being exposed for two hours to a heat 

 of 350°, were reduced to 15*88 grs. This residue was still 

 white, though it had a slight shade of buff. Being exposed 

 in a porcelain crucible to the heat of a spirit lamp, it gra- 

 dually blackened, without melting, and at last caught fire 

 and left a black powder, which continued for some time to 

 glow, till it was converted into peroxide of tin, weighing 

 12-57 grs. Equivalent to 10-1289 grs. of protoxide. If 



