§ 116. BONE-MEAL. 229 



bone-meal is under examination, a larger quantity, about 

 50 grms., should be incinerated in order to get the ash for 

 treatment with acid. 



e. Complete analysis of the ash. — Treat a portion of 

 the solution obtained in d according to Scheme IV., § 91, 

 taking 50-100 c.c. for a and the same for h. This exami- 

 nation is, in genera], unnecessary, if the only object of the 

 analysis is to determine the agricultural value of the 

 article. 



/*. Fat. — Exhaust a weighed quantity of the finely pul- 

 verized meal with ether, dry the residue at 125° C, and 

 count the loss as fat (§ 87). 



g. Gelatine. — The gelatinous substances may be esti- 

 mated by the diiference between the total loss on ignition 

 and the sum of the water and fat. 



K Fineness of division of the meal. — The value of 



bone-meal depends not only upon its chemical composition, 

 but also upon the fineness of the powder. 



To test the substance in this respect, it should be passed 

 through sieves of difierent degrees of fineness; and it is 

 important that all chemists should use sieves of the same 

 kind, so that the results obtained by different persons can 

 be compared with each other. 



Wolff recommends the use of the three finest sieves of 

 the set made by Hugershoff, in Leipzig, the first of which 



(I) has 1089 meshes in a square centimetre, the second 



(II) 484 meshes, and the third (III) 256. The residue, 

 that will not pass through the coarsest sieve, should be 

 examined, in order to see whether it is made up largely 

 of grains which would pass through a little coarser sieve 

 still, or of large splinters. 



One bone meal of excellent quality, analyzed by "Wolff, 

 contained 60°|, of No. I., 20°|„ of No. II., and lO^l^of 

 No. III. 



