POTASSIC MANURES, 305 



TABLE CIIL— ANALYSIS OF MOTHER LIQUOR FROM POTASSIUM 



CHLORIDE. 



Magnesium sulphate 2'-^ to 2-6 



,, chloride 



Potassium „ 

 Common salt .... 



19-5 to 20-9. 

 5-1 to 6 

 2 to :-i 



In the evaporation the greater part of the common salt separates out 

 because it is less soluble when hot than when cold, at the same time 

 as the double salt of potassium and magnesium (schoenite), which is 

 hardly soluble. This mixture of residual salts often contains 7-5 per 

 cent of potassium, which corresponds to 12 per cent of potassium chlo- 

 ride, or to 14 per cent of potassium sulphate. It is utilized by either 

 extracting the common salt from it or by converting it into manure 

 of low strength. In rational manufacture the residual salt should 

 be washed in the pan itself ; for this purpose the mother liquor II 

 is used, as the salt as well as the pan itself is still very hot. When 

 the evaporated solution is run off, the mother liquor with which 

 the pan is drenched, heats rapidly and then dissolves the greater 

 part of the potassium salt which is still contained therein. This 

 solution is facilitated by stirring. When the density of the solution 

 determined whilst boiling reaches 34-5 to 35° B., it is run through 

 wrought-iron gutters into special crystalHzers, where it deposits not 

 potassium chloride, but a salt with tetrahedral crystals, the compo- 

 sition of which is analogous to carnallite. If the solution was 

 sufficiently concentrated, the liquid which flows from the carnallite 

 crystals (final liquid) only contains 1 to 1-5 per cent of potassium 

 chloride, and in addition : — 



Per cent. 



Magnesium chloride 26 to 28 



,, sulphate ....... 4 



Common salt . . . . . . . . 2 „ 4 



In certain factories the bromine is extracted, in others the magnesia. 

 The artificial carnallite thus obtained is dissolved in water in smaller 

 pans than those used to dissolve the crude salt. The solution testing 

 32 to 33*^ B. is run into vats, where it deposits potassium chloride 

 more pure than that got from the crude salt. The mother liquor 

 of this salt is added to the first. As the carnallite from whence it 

 comes contains less common salt than the crude salt, this mother 

 Hquor yields little residual salt. The salt yielded by artificial car- 

 nallite is clarified with very little water, and then yields very high 

 strength potassium chloride (95 to 98 per cent). 



Drying the Chloride of Potassium. — In most factories potassium 

 chloride is dried in reverberatory furnaces. In recently erected fac- 

 tories the drying is conducted in cylindrical coil -heated tanks, in 

 which an agitator with blades revolves, and a roller compressor. 



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