40 THE CONNECTICUT' AGEICULTURAL 



The calculations are as follows : 



79 X 42 -T- 100 X 15 = $4.98 



79 X 33 -T- 100 X 14 = 3.64 



79 X 22 -T- 100 X 13 = 2.26 



79 X 3 -f- 100 X 12 = .28 



Estimated value of nitrogen= $11.16 



464.2 X 42 -^ TOO X 6 =$11.71 



464.2 X 33 

 464.2 X 22 



100 X 5i = 8.42 

 100 X 6 = 5.11 



464.2 X 3 -f- 400 X 4+ = .63- 



Estimated value of phosphoric acid= $25.87 



Total estimated value= $37.03 



This result agrees with the cost ($36.00) within $1.03. 



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, plastei', 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. Lister's Bone usually, and this year Raf- 

 ferty & Williams' Bone, contain a considerable, or even a large, 

 percentage of salt-cake ; of sample 552, 48 per cent, passed the 

 finest sieve, but the sample yielded to water 38 per cent, of solu- 

 ble matter, chiefly salt-cake, which mostly jDassed the finer sieves. 

 In such cases, the several grades as obtained by sifting must be 

 separately examined and the amounts of foi*eign 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 com- 

 plicated 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 diflferent portions 

 of the same lot of fertilizer, or in diftercnt 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. 



