552 AGRICULTURAL ANALYSIS 



evaporated upon the water bath with a sufficient amount of pla- 

 tinic chlorid. The residue of potassium platinochlorid is washed 

 with 90 per cent, alcohol, dried at 120, and weighed. 



(6) If it be desired to determine separately the quantity of 

 potash present in the form of sulfate and in the form of chlorid, 

 as, for example, in kainit and in sulfate of potash, or if it is to be 

 determined whether potassium sulfate is in combination with a 

 proportionate amount of magnesium chlorid, as in kainit, or in 

 combination with magnesium sulfate alone, as in schonit, it then 

 becomes necessary to determine besides potash the percentages 

 of chlorin, sulfuric acid, lime, magnesia, the total alkalies, water, 

 t and the residue insoluble in water. For this purpose 100 

 grams of the sample are dissolved, the solution is filtered, the 

 filter washed, and the filtrate made up to one liter ; a part of the 

 liquid is taken for the determination of sulfuric acid, by precipi- 

 tating with barium chlorid, and another part for the determina- 

 tion of lime and magnesia. For the determination of the alkali 

 chlorids, 100 cubic centimeters of the solution, corresponding to 

 10 grams substance, are acidulated with hydrochloric, and, after 

 heating to boiling, the sulfuric acid is completely precipitated 

 with barium chlorid, with the precaution of using not more of 

 the barium solution than is necessary for the complete precipita- 

 tion. Fifty cubic centimeters of the filtered solution, correspond- 

 ing to one gram substance, are evaporated to dryness in order to 

 drive off the hydrochloric acid. Magnesium chlorid is decom- 

 posed by igniting with oxalic acid. After ignition, the residue 

 is moistened with a little ammonium carbonate for the purpose 

 of converting the calcium oxid that may have been formed into 

 calcium carbonate. The alkali chlorids, which are entirely free 

 of lime and magnesia, are weighed, and potassium chlorid is de- 

 termined by means of platinic chlorid or perchloric acid. The 

 amount of sodium chlorid is obtained by deducting potassium 

 chlorid from the mixed chlorids. 



Estimation of Water. For the water determination five grams 

 of the sample are ignited and the loss of weight is determined. 

 The ignited mass is dissolved in water, and for the purpose of 

 determining the quantity of magnesium chlorid that may have 



