I30 PHOSPHATIC MANURES 



Ca2H2(P04)2, and is mixed with iron and aluminium phosphates 

 and silica, and occasionally with a small quantity of organic matter. 

 Although a complete analysis is described below, it is more usual 

 only to estimate the moisture and the "total" and " water soluble" 

 phosphates. 



113. Moisture and Combined Water. 



Two grams of the manure are weighed on a watch- 

 glass and heated for five hours at ioo° C. in the water- 

 oven. The loss in weight is hygroscopic moisture. The 

 chemically combined water is determined by heating 

 the dry manure to constant weight in the air-oven at 

 150° C. 



114. Organic Matter. 



About 3 grams of the superphosphate are weighed 

 into a platinum dish and milk of lime added until 

 distinctly alkaline. The mass is mixed well with a 

 glass rod, evaporated down on the water-bath, and 

 dried in the air-oven at 150° C. to constant weight. The 

 dish and its contents are then ignited and again weighed. 

 The loss represents organic matter. 



The nitrogenous material (if any) may be estimated 

 in 2 to 3 grams of the original manure by the ordinary 

 Kjeldahl method. 



115. Sandy Silica, etc. 



The residue from the determination of the moisture 

 is digested with hot dilute hydrochloric acid and filtered. 

 The insoluble residue is washed with water, dried, and 

 ignited. The residue is sand, etc. 



116. Phosphates. 



{a) Water Soluble Phosphate. — The superphosphate 

 is ground in a mortar, and 2 grams of the powdered 



