556 AGRICULTURAL ANALYSIS 



and washed with strong alcohol, care being taken that the liquid 

 does not touch the edge of the filter. The filtration can be car- 

 ried on under a moderate pressure. The complete washing of 

 the potassium platinochlorid can be easily accomplished upon the 

 filter. By the use of hot alcohol the process may be greatly 

 hastened. The filter and the precipitate, after as much of the 

 alcohol wash has been removed as is possible, are dried at 120 

 to 130 to constant weight and weighed while still warm. One 

 milligram of the potassium platinochlorid thus obtained corre- 

 sponds to a tenth per cent, of potassium chlorid. 



(2) By Perchloric Acid. 13.455 grams of the well ground 

 sample are dissolved in water and made up to 500 cubic centi- 

 meters after the addition of from three to four cubic centi- 

 meters of the acid solution of barium chlorid, containing 122 

 grams of the crystallized salt and 50 cubic centimeters of strong 

 hydrochloric acid in one liter. Twenty cubic centimeters of the 

 filtrate (=0.5382 gram of the sample) are placed in a shallow 

 glass or blue enamelled porcelain basin of about 10 centimeters 

 diameter. One and a half times the quantity of perchloric acid of 

 1.125 specific gravity necessary to decompose all the salts is 

 added. The mass is then evaporated on the water-bath until the 

 odor of hydrochloric acid disappears, and white fumes of per- 

 chloric acid begin to come off. After cooling, the residue is 

 washed with 96 per cent, alcohol to which 0.2 per cent, of per- 

 chloric acid has been added. In washing, 20 cubic centimeters of 

 the alcohol are first added to the basin and the residue is thor- 

 oughly rubbed down in the liquid, which is then decanted through 

 a tared filter. The washing is repeated, several times by decanta- 

 tion and finally on the filter. The final washing requires pure al- 

 cohol (as little as possible) to remove free perchloric acid. The 

 filter and residue are dried and weighed in the same manner 

 as in the platinum process. 



One milligram potassium perchlorate represents o.i per cent, 

 of potassium chlorid. 



Estimation of Sodium Chlorid. For the estimation of the so- 

 dium chlorid which may present in the potassium chlorid, 12.5 

 grams of the latter salt are dissolved in a quarter liter flask with 



