132-135] Preparation in the Laboratory 91 



132. Soils. — Soils must be first dried at 6o° to 70 C, 

 then sifted through a J-inch sieve. The stones which will not 

 pass the sieve are rejected, and the rest treated exactly like a 

 mineral. 



133. Moist Substances. — Superphosphates, dissolved 

 bones, and acid manures. These are the most difficult of all to 

 obtain in a fine state. They should be sifted, and the larger 

 pieces broken up by gently rolling round in an iron mortar. 

 Just before weighing out in the laboratory they should be 

 pounded into a homogeneous paste in a small iron mortar. 



134. Soft Substances.— Wool waste, shoddy, &c. Must 

 be cut up small with scissors. 



135. Cakes. — May be broken into pieces, a fair sample 

 of the pieces selected, and ground fine in the mill. 



