548 AGRICULTURAL ANALYSIS 



filtrate are evaporated in a platinum dish. After evaporation the 

 ammonium salts are driven off by careful ignition, the residue 

 taken up with hot water and filtered through as small a filter as 

 possible into a porcelain dish, the magnesia remaining in the 

 precipitate. The filtrate is acidified with a few drops of hydro- 

 chloric acid, 10 cubic centimeters of platinic chlorid added and 

 the further determination conducted as with kainit. 



468. Dutch Method. The process used at the Royal Agri- 

 cultural Station of Holland is almost identical with that em- 

 ployed at Halle. 37 



A. Method for Stassfurt and other Potash Salts. The neces- 

 sary reagents are: 



1. A dilute solution of barium chlorid. 



2. A solution of platinic chlorid containing one gram of plati- 

 num in 10 cubic centimeters. It must be wholly free from plati- 

 nous chlorid and nitric acid, and partially freed from an excess 

 of hydrochloric acid by repeated evaporations with water. 



3. Alcohol of 80 per cent, strength by volume. 



The methods of bringing the potash into solution and of pre- 

 cipitating the sulfuric acid are the same as for the Halle pro- 

 cess described above. 



To 50 cubic centimeters of the solution add 20 cubic centime- 

 ters of the platinum solution and evaporate the mixture nearly 

 to dryness. Add a sufficient quantity of 80 per cent, alcohol 

 and stir for some time. Allow to stand and then filter through 

 a gooch dried at 120. Finally wash with 80 per cent, alcohol 

 dry at 120, and weigh. 



B. Method for Potash-Superphosphate and other mixed Fer- 

 tilizers. The reagents necessary are the same as under A, and, 

 in addition, a saturated solution of barium hydrate and a solu- 

 tion of ammonium carbonate mixed with ammonia. 



Boil 20 grams of the substance with water for half an hour, 

 cool, make up to half a liter and filter. Boil 50 cubic centimeters 

 of the filtrate, and add barium chlorid till no more precipitate 

 forms. Mix with baryta water to strong alkaline reaction, cool, 

 make up to 100 cubic centimeters and filter. Raise 50 cubic cen- 

 " Methoden von Onderzoek aan de Rijkslandbouwproefstations, 1894 : 6. 



