59O AGRICULTURAL ANALYSIS 



carnallit or bergkieserit 13.455 grams, and in the case of kainit, 

 sylvinit and hartsalz 15.7225 grams are dissolved in about 300 cu- 

 bic centimeters of water with 15 cubic centimeters of concen- 

 trated hydrochloric acid in a 500 cubic centimeter flask. The 

 solution is heated to the boiling point and the sul- 

 furic acid precipitated by barium chlorid. In this case 

 a slight excess of barium chlorid is without any hurtful 

 influence upon the exactness of the process, since chlorid of 

 barium is converted into barium perchlorid by the perchloric acid 

 and this salt is easily soluble in alcohol. For the complete pre- 

 cipitation of sulfuric acid there are required, in the case of car- 

 nallit, from 24 to 40 cubic centimeters, and, in the case of kainit, 

 from 65 to 80 cubic centimeters of normal barium chlorid 

 solution, containing 122 grams of BaCl 2 ,2H 2 O, and 50 cubic 

 centimeters of concentrated hydrochloric acid in one liter. After 

 cooling, the flask is filled to the mark and its contents filtered 

 through a dry, double folded filter of about 18 centimeters diam- 

 eter. When filtered, 20 cubic centimeters are evaporated in a 

 flat, dark-blue glazed porcelain dish of about 10 centimeters 

 diameter with five cubic centimeters of perchloric acid of 1.125 

 specific gravity until the odor of hydrochloric acid has disap- 

 peared and white clouds of perchloric acid are evolved. The 

 residue is treated with about 20 cubic centimeters of 96 per cent, 

 alcohol and carefully rubbed in order to break up the mass into 

 as fine particles as possible. After standing for a short time the 

 supernatant liquid is filtered through a filter prepared as in the 

 platinum method given above or through a gooch. 



The rubbing of the potassium perchlorate is repeated twice 

 more, but not with pure 96 per cent, alcohol, but with alcohol to 

 which 0.2 per cent, of perchloric acid has been added. Finally, 

 in order to remove the perchloric acid, the filter and the precipi- 

 tate thereon are washed with a spray of 96 per cent, alcohol, 

 using as little thereof as possible and drying and weighing as in 

 the platinum method. In this process one milligram of potas-, 

 sium perchlorate, corresponds to o.io per cent, of potassium., 

 chlorate or of potassium sulfate in the raw material. 



495. Influence of Carbonates. In the method of determining 



