1835.] Racetnic Acid, 247 



grs. We, therefore, want 15*44 grs. of oxide of tin, and 

 37-3 grs. of racemic acid. Let us see how far these will be 

 found in the water employed in washing this precipitate ; 

 The common salt found should amount to 75 grs., of which 

 we have found not quite 1 gr. in the precipitated salt. 



2. 114-7 grs. of Salt from first Washing. — Of this salt 

 24*9 grs. were heated over a spirit lamp. It melted, 

 frothed, and boiled up, and, after ignition, left a white 

 salt, resembling common salt, and weighing 16*3 grs. Be- 

 ing digested in water 12*3 grs. of common salt were dis- 

 solved, and 4*264 grs. of peroxide of tin remained = 3*803 

 grs. of protoxide of tin. 



It is obvious that the whole 114*7 grs. of salt would have 

 yielded Common salt . , . 5Q'QQ 



Protoxide of tin . . 17*52 

 Racemic acid and water 40*52 



114*70 



3. 23 grs. of salt from second washing. This salt being 

 treated in the same way produced 11*14 grs. of common 

 salt, and 6*069 grs. of protoxide of tin. The racemic acid 

 and water, therefore, was 5*791 grs. 



4. 8*1 gr. of Salt from third Washing. — This portion was 

 accidentally lost ; but, from its appearance, it could not 

 differ much from the salt from the second washing. It 

 must have contained all the common salt washing to make 

 up the 75 grs. Now, this amounts to 6*21 grs. Hence, 

 the oxide of tin, racemic acid and water which it contained 

 could only amount to 1*89 grs. 



The protoxide of tin exceeds the true quantity by 8*15 

 grs. I do not know the reason of this; unless we are to 

 ascribe the apparent excess to a residue of charcoal in the 

 residue of the salt from the first washing. I had thrown 

 this residue away before I was aware of the excess. But 

 the peroxide of tin from the second portion of the water, 

 before it was treated with nitric acid, contained rather more 

 than the fourth part of its weight of charcoal. This correc- 

 tion, applied to the protoxide of tin in the second salt, would 

 reduce it to 13*39 grs., and, of course, elevate the racemic 

 acid and water to 44*65. After this correction is applied 

 there still remains an excess of 4*02 grs., which can only 



