SEDIMENT A TION METHOD 85 



of vegetable matter are picked out, and the residue 

 weighed as " stones." 



The material passing the sieve is again exposed to 

 the atmosphere for some time, and is stored in a bottle 

 for further examination, and labelled "air-dry fine 

 earth." 



65. Mechanical Analysis by Sedimentation} 



(a) Ten grams of the air-dry fine earth are treated 



N 

 in a beaker with 100 c.c. of — HCl, worked with a glass 



rod fitted with a small rubber stopper so as to break up 

 any lumps, and allowed to stand for one hour. This 

 dissolves the carbonates and breaks up the humates, 

 and resolves the soil into its ultimate particles. 



The soil is filtered on a tared filter paper and washed 

 with distilled water until the filtrate is quite free from 

 acid, after which it is dried and weighed. The loss 

 suffered by the soil represents soluble material and 

 hygroscopic moisture. The soil is then carefully washed 

 on to a small sieve of 100 meshes to the linear inch 

 with ammoniacal water, prepared by dissolving i c.c. 

 of strong ammonia in half a litre of water. The muddy 

 liquid passing through the sieve is collected in a beaker 

 marked at a distance of 8 cm. from the bottom. The 

 portion remaining on the sieve is dried and weighed, 

 and separated into two portions by means of a sieve 

 with I mm. meshes, the coarser portion being designated 

 ^^fine gravel" and that passing through the sieve as 

 *' coarse sand." Further separation is effected by 

 subsidence. 



{b) The muddy liquid from (a) is well triturated with 

 the rubber pestle, and ammoniacal water added up to 



^ Official method of the Agricultural Education Association. 



F 2 



