254 AMERICAN MANURES. 



oxalate of ammonia was added. The precipitate 

 obtained was collected at once on a double filter, 

 and to the cool and strongly ammoniacal filtrate, 

 were added, 6 to 10 c.c. of an ammoniacal ammo- 

 nio-sulphate of magnesia solution each c.c. of 

 which corresponds to 0.0358 gramme anhydrous 

 phosphoric acid. The filtrate and wash water 

 measured 250 to 300 c.c., and for every 54c.c. of 

 the same, 0.000637 gramme phosphoric acid was 

 allowed. 



METHOD FOE SOLUBLE PHOSPHORIC ACID. 



Substance = 20 grammes. 



Fluid = 1000 c. c. 



Fluid taken = 100 c. c. 2 grammes substance. 



The substance was triturated in a mortar with 

 distilled water, at 60 or 70/the powder allowed 

 to settle, and the fluid decanted. This operation 

 was repeated till 4 litre of fluid was obtained, 

 when the powder was collected on a filter and 

 washed with distilled water till the filtrate mea- 

 sured one litre. The phosphoric acid, as in the 

 previous instance, was determined gravimetri- 

 cally. 



NOTE. In one or two instances, instead of 1 to 2 grammes, 

 10 grammes of the substance were taken for the phosphoric acid 

 determination. 



CONCLUDING REMARKS. 



Manufacturers of fertilizers attach great im- 

 portance to the certificates of farmers, and it is 

 considered a strong point as an evidence of the 



