MURIATE OF POTASH, POTASSIUM CHLORIDE 233 



water became more and more concentrated in salts until 

 finally the least soluble were deposited. On top of these 

 compounds other salts were deposited layer by layer. 

 Intermittent additions of sea water from outside caused a 

 dilution of the water within, and deposition of salt was 

 consequently interrupted, causing alternate layers of less 

 soluble and more soluble compounds as evaporation went on. 

 Geologic changes brought about finally the deposition of 

 various sedimentary rocks and finally a layer of impervious 

 clay which protected the soluble salts from solution in rain 

 water. 



The bottom layers of these beds are composed of anhydrite 

 (sulphate of calcium) and rock salt. Next comes the so-called 

 polyhalite region (sulphates of calcium, magnesium, and 

 potassium) ; then the kieserite region (magnesium sulphate) ; 

 and finally the carnallite region (chlorides of potassium and 

 magnesium). The latter is a bed ranging from 50 to 130 

 feet in thickness, from which most of the potash salts are 

 obtained. Due to the intermittent deposition of salts, 

 partial solution from infiltration of rainwater, and redepo- 

 sition, the layers of salts are not perfectly distinct and not 

 always in the same order. For instance, lavers of anhvdrite 

 and rock salt intersperse the other salts, together with 

 minerals, such as sylvine (potassium chloride) and kainite 

 (sulphate and chloride of magnesium and potassium). 



178. Muriate of Potash, Potassium Chloride, KC1. — This is 

 the most widely used potash fertilizer. It is manufactured 

 from carnallite which occurs mixed with rock salt and other 

 minerals, and contains only 9 per cent, actual potash. 

 By dissolving carnallite in hot magnesium chloride solution, 

 boiling, and crystallizing, there is obtained a muriate con- 

 taining about 20 per cent, potash and called Potash Manure 

 Salt. On further evaporation and crystallization of the 

 mother liquor a pure carnallite (KCl.MgCl.6H2O) is obtained 

 (Fig. 54). This salt on being treated just like the crude 

 carnallite vields the commercial muriate with one crystalli- 

 zation. 



There are three grades of muriate on the market, 80 per 

 cent., 95 per cent., and 98 per cent., which contain respec- 



