(3) _Estimation of Potash (K₂O) in Raw Potash Salts._—(_a_) For the determination of potash alone in carnallit, kainit, and sylvinit one hundred grams of the well-mixed sample are put into a graduated flask holding one liter and dissolved by boiling with half a liter of water, acidulated with ten cubic centimeters of hydrochloric. The purpose of adding hydrochloric acid is to bring any polyhalit that might be present in the salts into solution and which it is difficult to dissolve in pure water. After dissolving and cooling the flask is filled up to the mark. The solution, after mixing, is filtered through a dry filter and 100 cubic centimeters of the filtrate, corresponding to ten grams substance, are put into a half liter flask by means of a pipette. After the addition of 200-300 cubic centimeters of water the solution is heated to boiling and the sulfuric acid accurately precipitated with normal barium chlorid solution, containing 104 grams of the dry salt in one liter. The volume of the precipitate is calculated from the amount of barium solution used and from the specific gravity of the barium sulfate. After cooling, the flask is filled up with water as far above the mark as equals the volume of the calculated barium precipitate, and, after thorough mixing, the solution is filtered again through a dry filter. Fifty cubic centimeters of this filtrate, corresponding to one gram substance, are evaporated upon the water-bath with a sufficient amount of platinic chlorid. The residue of potassium platinochlorid is washed with ninety per cent alcohol, dried at 120°, and weighed.