542 AGRICULTURAL ANALYSIS 



responding to one gram of the sample, nearly to dryness, add one 

 cubic centimeter of dilute sulfuric acid (i to i), evaporate to- 

 dryness and ignite to whiteness. As all the potash is in form of 

 sulfate, no loss need be apprehended by volatilization of potash, 

 and a full red heat must be maintained until the residue is per- 

 fectly white. Dissolve the residue in hot water, using at least 

 20 cubic centimeters for each decigram of K 2 O, add a few drops 

 of hydrochloric acid and platinum solution in excess. Evaporate 

 on a water bath to a thick paste and treat the residue with 80 

 per cent, alcohol, specific gravity 0.8645, avoiding the absorp- 

 tion of ammonia. Wash the precipitate thoroughly with 80 per 

 cent, alcohol both by decantation and on the filter, continuing the 

 washing after the filtrate is colorless. Wash finally with 10 cubic 

 centimeters of the ammonium chlorid solution (i) (a) to remove 

 impurities from the precipitate, and repeat this washing five or 

 six times. Wash again thoroughly with 80 per cent, alcohol, 

 and dry the precipitate for 30 minutes at 100. The precipitate 

 should be perfectly soluble in water. 



(6) Muriate of potash. Dilute 25 cubic centimeters of the 

 solution, prepared according to (2) (a), with 25 cubic centi- 

 meters of water, acidify with a few drops of hydrochloric acid, 

 add 10 cubic centimeters of platinum solution and evaporate to 

 a thick paste. Treat the residue as under (3) (a). 



(c) Sulfate of potash, sulfate of potash and magnesia, and 

 kainit. Dilute 25 cubic centimeters of the solution, prepared ac- 

 cording to (2) (a), with 25 cubic centimeters of water, acidify 

 with a few drops of hydrochloric acid and add 15 cubic centime- 

 ters of platinum solution. Evaporate the mixture and proceed as 

 directed under (3) (a), except that 25 cubic centimeter portions 

 of ammonium chlorid solution should be used. 



(rf) Water-soluble potash in wood-ashes and cotton-hull ashes. 

 Use above method making the solution according to (2) (a),, 

 and pay special attention to the last sentence (3) (a). 



464. Optional Method. (i) Preparation of reagent. Platinum 

 solution. The platinum solution used is the same as that de- 

 scribed under the lindo-gladding method. 



(2) Method of making solution. The solution is prepared as 



