364 Analysis of Shells. 



store the carbonic acid, its weight was 390 grs. The arerage of 

 the two is 389.85 grs. for the earthy or saline matter in 400 grs. of 

 the powdered shell. l 



Two parallel experiments were now performed, each with 500 

 grs. of the powdered shell, exposed to a white heat in a Hessian 

 crucible. Treated as before with carbonate of ammonia, they gave 

 487 and 486.6 respectively, the average of which corresponds to 



389.44 for 400 grains. 



This differs from the results with the platinum crucible, by four 

 tenths of a grain, caused no doubt by a small portion adhering una- 

 voidably to the interior of the crucible. I therefore accept the re- 

 suit given by the platinum. 



Subtracting 389.85 grs. from 400, we have 10.15 for moisture 

 and animal matter. The moisture was already (5) found to be 6.5 

 grs. The remaining 3.65 grs. would therefore appear to be animal 

 matter. By the direct process however we found the animal matter 

 to amount only to 1.8 grs. It is to be observed that a small portion 

 of the difference between these two numbers, 3.65 and 1.8 must be 

 ascribed to the unavoidable loss in transferring the calcined powder 

 from the crucible to the capsule in treating it with carbonate of am- 

 monia, and again, in the operation of weighing. The remainder of 

 the difference may probably arise from the disappearance of a small 

 portion of animal matter by solution in the acid. We may therefore 

 put down for soluble animal matter and loss 1.85 grains. 



6. The mass remaining after the treatment with carbonate of am- 

 monia, consisted as is evident from preceding experiments, of carbon- 

 ate of lime, phosphate of lime and silex. The total weight of the 

 mass was found to be 389.85 grains. Deducting from this the sum 

 of 7.5 and 1.8 grs. the quantities of phosphate and silex, we have 

 380.75 grs. for the quantity of carbonate of lime in 400 grs. of oys- 

 ter shell. 



The results when summed up are as follows, 



Carbonate of lime, ----- 380.75 



Phosphate of lime, .... 7.50 



Silex (probably accidental,) - 1.60 



Water, - 



6.50 



Insoluble animal matter, - 1.80 



Loss, and soluble animal matter, - - - 1.85 



400.00 



