558 AGRICULTURAL, ANALYSIS 



tained in the high grade sulfates of commerce is determined in 

 the following manner : In a half liter flask are placed 8.9275 

 grams of the finely ground sample which is dissolved in about 350 

 cubic centimeters of boiling water after the addition of 20 cubic 

 centimeters of hydrochloric acid. The sulfuric acid is thrown 

 out by the addition, drop by drop, of a barium chlorid solution. 

 the contents of the flask being kept boiling meanwhile and thor- 

 oughly stirred. The barium chlorid solution is delivered from a 

 burette with a glass stop-cock. From time to time the addition 

 of the barium chlorid is stopped and the upper part of the liquid 

 allowed to become clear by the subsidence of the barium sulfate. 

 It is then noticed whether or not an additional drop of the barium 

 chlorid solution produces a turbidity. A convenient method is 

 to drop a small crystal of barium chlorid into the clear super- 

 natant liquid. Any excess of barium chlorid is removed by the 

 careful attention of sulfuric acid. After the precipitation is com- 

 plete and the contents of the flask are cooled, it is filled up to 

 the mark with water and its contents filtered. Twenty cubic 

 centimeters of the filtrate, corresponding to 0.3571 gram of the 

 original salt are precipitated by platinic chlorid in the usual man- 

 ner and the resulting potassium platinochlorid collected and 

 weighed. One milligram of the potassium platinochlorid thus ob- 

 tained corresponds to one-tenth per cent, of potassium sulfate in 

 the original salt. To the percentage of potassium sulfate thus 

 found three-tenths per cent, are to be added for a correction when 

 high-grade potassium sulfate is examined. If the sample be a 

 high-grade sulfate of potassium and magnesium no correction 

 should be applied. 



Estimation of Potassium Chlorid and Potassium Sulfate in Cal- 

 cined Manurial Salts. In these salts 15.281 grams of potassium 

 chlorid or 17.847 grams of potassium sulfate are dissolved in a 

 half liter flask after the addition of 10 cubic centimeters of hy- 

 drochloric acid. The flask is filled to the mark and its contents 

 filtered and 250 cubic centimeters placed in a half liter flask and 

 treated with barium chlorid solution as indicated above. The 

 rest of the operation is exactly as has been described. In each 



