272 AGRICULTURAL EXPERIMENT STATION. [Jail. 



Methods of Fertilizer Analysis. 



Preparation of Sample. — The entire available sample is 

 spread upon a smooth, hard surface, and intimately mixed 

 without grinding, all lumps being broken up with a spatula. 

 Unnecessary loss or gain of moisture is to be avoided. 

 Moisture: dry 2 grams in the air-bath at 100 to 110° C. to 

 a constant weight. 



1. Total Phosphoric Acid. — Weigh out 2 grams in a plati- 

 num crucible, and destroy the organic matter by carefully 

 burning in a muffle. Weigh when cool, to determine the " or- 

 ganic and volatile matter." Digest the crucible and contents 

 with dilute hydrochloric acid, until the solution of the latter 

 is complete. Filter, and evaporate the filtrate to complete 

 dryness. The " insoluble matter " on the filter is burned and 

 weighed. The residue left from the evaporation is taken up 

 with dilute nitric acid, if the molybdic method is to be fol- 

 lowed, but with hydrochloric acid if method (2) is preferred. 

 The solution after filtering is made up to a volume of 200 

 cubic centimetres with distilled water. 



(1) The molybdic method: 25 cubic centimetres of the 

 solution are digested in a water-bath at 6b° C. from one to 

 two hours, with an excess of molybdic solution. The pre- 

 cipitate is brought upon a filter, and washed with water 

 containing a little molybdic solution. It is then dissolved in 

 ammonia water, the solution nearly neutralized with hydro- 

 chloric acid, and magnesia mixture added slowly, with con- 

 stant stirring. The precipitate is allowed to stand at least 

 three hours, when it is filtered through a Gooch crucible, 

 washed with dilute ammonia, ignited and weighed. 



(2) The following method is occasionally employed when 

 phosphates of iron and alumina are present in small quanti- 

 ties only : To 50 cubic centimetres of the hydrochloric acid 

 solution add ammonia in slight excess. After standing a 

 few minutes, acidify with acetic acid, and filter off the phos- 

 phates of iron and alumina, washing carefully with water. 

 To the filtrate add sufficient oxalate of ammonia to precipi- 

 tate all the lime ; digest for several hours at a temperature 

 below boiling, and filter through double filters which have 



