232 Analysis of Soils. [Oct., 



3. Analysis of the Soluble Salts in a Soil. 



We have also to determine what soluble salts exist in the soil. 

 It is necessary to operate on 1000 grains of the soil in order to 

 obtain an appreciable quantity of saline matter. We boil the 

 soil in distilled water, then filter, evaporate the solution to dry- 

 ness in a platina capsule, and heat sufficiently to burn off all the 

 organic matters. Then we dissolve the salts in water and test 

 for the acids and bases which are present, namely, for sulphates 

 by means of a solution of acetate of baryta; for chlorides by 

 means of a solution of nitrate of silver, if the solution is neutral 

 a little phosphate of silver may also be precipitated. The pre- 

 cipitate may be analyzed to ascertain if any phosphate is present. 



We search for the bases of the salts on a part of the same so- 

 lution, namely, for lime by a solution of oxalate of ammonia; for 

 alumina by ammoniac; for oxide of iron by ferrocyanate of pot- 

 ash; for magnesia by phosphate of soda and ammonia; for potash 

 by chloroplatinic acid; for soda by observing if a portion of the 

 solution ev?iporated to dryness on a slip of platinum foil turns a 

 blue alcohol flame yellow. 



If the nitrates are suspected to be present, observe on burning 

 off the organic matter if any deflagration takes place. Nitrates 

 of potash, soda, or lime, leave when deflagrated the carbonates of 

 their bases, but nitrate of ammonia leaves no solid residue. It 

 deflagrates very readily, and is often present in soils. 



Sulphate of ammonia is to be sought for before burning off the 

 organic rnatter, for it would be expelled by the heat. It may 

 be separated by distilling a portion of the dried saline matter, 

 which is to be done in a tube retort; the sulphate of ammonia, 

 together with the muriate of ammonia, will be condensed in the 

 cool neck or receiver. It will form a white crust in the tube, 

 and may be dissolved out and tested by chloride of barium solu- 

 tion and by means of potash. The presence of chlorohydrate of 

 ammonia is determined by testing the solution, for chlorohydric 

 acid by means of nitiate of silver, which will give a white curdy 

 precipitate if chlorine is present. 



Soluble silicates of potash and soda are also to be sought for 



