EXPERIMENT STATION. 39 



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. 



In some instances a further source of error in valuation may 

 arise from the fact that the proportions of nitrogen and phos- 

 phoric acid are not the same in the finer and coarser portions of a 

 sample, which contains no adulterants, properly speaking, but 

 partly consists of meat, tendon, etc. 



There is, however, a limit beyond which it is useless to attempt 

 to refine the processes of valuation. When they become too 

 complicated or costly they defeat the object which they should 

 serve. It is sufficient that the errors of valuation are no greater 

 than those which arise from unavoidable variations in different 

 portions of the same lot of fertilizer, or in different lots of the 

 same brand. A difference of two or three dollars between cost 

 and estimated value cannot ordinarily demonstrate that either is 

 out of the way. 



Bone Manures. 



Analyses. 

 [See pages 40 and 41.] 



Sample 733 was very wet, which accounts for the low percent- 

 age of nitrogen' and phosphoric acid found in it. At the price 

 asked ($25.00 per ton) it is an excellent article for immediate use, 

 but in its moist state could not be kept long without decomposi- 

 tion and loss. 



In five of the samples analyzed this year the valuations fall 

 very considerably below the market price. In 731 and 804 this 

 IS caused chiefly by the coarseness of the bone. 770 contains 

 salt-cake in considerable quantity, as this brand of goods usually 

 does. 801 probably contains the same. 751 has 6.9 per cent, of 

 sulphuric acid combined Avith lime, being equivalent to 13.3 per 

 cent, of hydrated plastei-. 



Salt-cake is used as a drier and preservative to mix with bone 

 which would otherwise be too wet to handle and transport. No 

 secret is made of it by the manufacturers, nor is the mixture sold 

 as "pure" bone. But bone sold as "pure" which contains 13 per 

 cent, of land plaster has cleai-ly been adulterated. 



The average cost of bone this year, $35.29, exceeds the average 

 estimated value, $32.14, by |3.15. 



