METHODS FOR CONCENTRATED POTASH SALTS 555 



tained with this method are, according" to them, very inaccurate, 

 and always too low. This is explained by the fact that it is im- 

 possible to precipitate sulfuric acid without the same time pre- 

 cipitating some of the potash, unless it be in an acid solution. 



A separation of the alkaline earths, if potash alone is to be 

 determined, is superfluous, for the reason that calcium and mag- 

 nesium platinochlorid are soluble in 90 per cent, alcohol, even 

 with more facility than sodium platinochlorid. 



471. Methods for Concentrated Potash Salts. In the pre- 

 ceding paragraphs have been given the methods used by the 

 Stassfurt syndicate for the estimation of potash in the raw salts 

 as they come from the mines. Following are the methods used 

 by the same syndicate for the concentrated approximately pure 

 compounds and the other salts which accompany them. 40 



Potassium Chlorid. The following process is used for the esti- 

 mation of potassium and other constituents of the high grade 

 chlorids of commerce. In a half liter flask are placed 7.6401 

 grams of the finely powdered sample, which is dissolved and 

 made up to the mark. With salts which contain more than half 

 a per cent, of sulfuric acid the preliminary conversion of the sul- 

 fates into the corresponding chlorin compounds, by precipitation 

 with barium chlorid solution, is necessary. Twenty cubic centi- 

 meters of the above solution, corresponding to 0.3056 gram of 

 the salt, are placed in a flat porcelain dish having a diameter of 

 about 10 centimeters and, after the addition of five cubic centi- 

 meters of the platinic chlorid solution, evaporated on the water- 

 bath with constant stirring until, after cooling, the sirupy liquid 

 passes quickly into a fine crystalline condition. The evapora- 

 tion can be carried on to dryness without risk in the use of the 

 concentrated salts. In addition to the potassium chloroplatinate, 

 the principal ingredient is the corresponding sodium salt, and this 

 is more easily dissolved by alcohol when dry than when water is 

 present. The residue is rubbed into a fine powder with a glass 

 rod, mixed with 20 cubic centimeters of 96 per cent, alcohol, and 

 brought onto a filter moistened with alcohol and dried at 120, 



* Analytical Methods for the Examination of Potash Salts, Published 

 by the Kalisyndikat, Leopoldshall-Stassfurt, 1906. 



