246 Dr. Thomas Thomson on [Oct. 



loss of 8' 74 grs. proceeding from the salts of the second and 

 third waters used for washing the precipitates which had 

 been too strongly heated, and were in part charred. 



I shall now relate the experiments made to determine 

 the nature of these salts : 



1. The 119'21 gr. of Precipitate. — This was a chalky 

 powder, precisely similar to that above described. 20 grs. 

 of it, kept for 2J hours in the temperature of 340°, lost 

 1 gr. of weight. We see from this that it had been previ- 

 ously much better dried than the first racemate of tin 

 examined. Being more strongly heated, it blackened and 

 burned like tinder, leaving a yellowish powder, weighing 

 12-79 grs. 



This residue was digested in water, and the liquid being 

 evaporated to dryness, left 0'166 gr. of common salt. Con- 

 sequently, 12*624 grs. of the residue was peroxide of tin = 

 1125 grs. of protoxide. Hence, the 20 grs. examined must 

 have consisted of 



Water 1-000 



Protoxide of tin . . . 11-250 or 12-23 

 Racemic acid . . . 7-584 ,, 8-25 

 Common salt . . . 0*166 



20*000 

 The oxide of tin exceeds an atom by about one-half. 



We might, therefore, consider the salt as a subsesqui- 

 racemate of tin, not quite freed from common salt. I did 

 not wash it nearly as much as I had done the first precipi- 

 tate, from a suspicion that I had washed away a portion of 

 the racemic acid. Hence, the reason of the small residue 

 of common salt. 



It is obvious that the 119*21 grs. of precipitated salt were 

 composed of 



Water 5*9605 



Protoxide of tin . . 67*0557 

 Racemic acid . . . 45*2044 

 Common salt . . . 0*9894 



119*2100 

 The whole oxide of tin from the chloride ought to have 

 amounted to 82*5 grs. and the whole racemic acid to 82*5 



