EXPERIMENT STATION, 



4^ 



The result agrees with the cost price ($37.50) within 36 cents. 



When the sample of bone contains foreign matters introduced 

 as preservatives, dryers or adulterants, such as salt, salt-cake, 

 niter-cake, ground oyster-shells, spent lime, plaster, or soil, these 

 must be taken account of in the mechanical analysis, especially 

 since they would be likely, on sifting, to pass chiefly or entirely 

 into the finer grades. In such cases, the several grades as ob- 

 tained by sifting must be separately examined, and the amounts 

 of foreign matter which they contain must be suitably 'taken into 

 the account if an exact valuation is desired. 



A sino-le examination of this kind has been made in the case of 

 No. 884 Lister's Celebi-ated Ground Bone, which contains a con- 

 siderable quantity of salt cake and some salt. A second mechan- 

 ical analysis was made, agreeing essentially with the one given 

 on page 53, and nitrogen and phosphoric acid were determined in 

 each of the grades. The results were as follows reckoned on 100 



100 



2.30 



12.85 



The total nitrogen (2.30 pounds per hundred) and the total 

 phosphoric acid (12.85 pounds per hundred) agree reasonably well 

 with the amounts found by the usual method of analysis, viz : 

 citrogen, 2.41 ; phosphoric acid, 12.55. It will be seen that the 

 percentage amount of nitrogen and phosphoric acid in the coarsest 

 portion is more than twice that in the finest portion, which shows 

 that the most of the foreign material — salt, salt-cake, etc. — sifts 

 out with the finer part of the bone. Now, in computing the esti- 

 mated value, nitrogen and phosphoric acid have a valuation which 

 is higher in the finer grades (see page 24), and it is assumed that 

 the percentage composition of all the grades is alike. If, as in 

 this case, the finer grades have a lower percentage of nitrogen 

 and phosphoric acid than the coarser, the valuation will be too 

 high. To see whether the error is a considerable one, the valua- 

 tion has been recalculated from the amounts of nitrogen and 

 phosphoric acid actually found in each grade, and is 120.06 per 



