METHODS FOR PHOSPHORIC ACID USED IN NORWAY 69 



ness, are insufficient. 48 In those countries are found many, in part, 

 poorly pulverized, and badly mixed manures, such as ammonium- 

 superphosphate, potassium-superphosphate, and potassium-ammo- 

 nium-superphosphate, and these can not usually be so well pul- 

 verized and mixed that one can secure a true average sample of 

 from two to two and five-tenths grams. Care in the analysis is use - 

 less when the material employed does not represent the average 

 conditions of the materials investigated. Therefore, in the coun- 

 tries named, often from 10 to 20 grams, and almost never less 

 than five grams of substance are used in the preparation of the 

 solutions, except, for instance, in the determination of nitrogen 

 and reverted phosphoric acid. 



78. Methods for Phosphoric Acid Used in the Norway Stations. 40 

 i. Description of the Method for Total Phosphoric Acid. For 

 determining the phosphoric acid in bone-meal, fish-guano, and 

 superphosphates, five grams of the substance, with 20 cubic 

 centimeters of nitric acid of 1.42 specific gravity, and 50 cubic 

 centimeters of sulfuric acid of 1.8 specific gravity, are boiled half 

 an hour in a half liter flask, diluted with water, and after cool- 

 ing, made up to the mark. Fifty cubic centimeters of the filtrate 

 are made alkaline with ammonia, then acid with nitric acid, pre- 

 cipitated with 50 cubic centimeters of molybdic solution for every 

 one-tenth gram of phosphorus pentoxid present, heated over 

 the water bath for one hour, and allowed to stand 12 hours, 

 when the supernatant liquid is separated by decantation, the pre- 

 cipitate washed thoroughly with dilute molybdate solution (1:4), 

 dissolved in warm dilute ammonia, and the filter washed with hot 

 water. The ammoniacal solution is neutralized with hydrochloric 

 acid, cooled, mixed, drop by drop, with constant stirring, with 

 from 10 to 20 cubic centimeters of magnesia mixture, and 

 after a quarter of an hour one-third the volume of 10 per cent, 

 ammonia is added. This, after standing two hours, is filtered, 

 washed with five per cent, ammonia until the disappearance of 

 Ihe chlorin reaction, dried, burned in an open crucible over a 

 bunsen, and finally, for a quarter of an hour, in a covered cru- 

 cible over the blast. 



48 Division of Chemistry, Bulletin 47, 1896 : 85. 



49 Solberg, Division of Chemistry, Bulletin 47, 1896 : 83. 



