104 MANUFACTURE OF FERTILIZING MATERIALS 



out. The residue remaining in the pan con- 

 tains a large proportion of kieserite, common 

 salt, and about 2 to 4 per cent of potash 

 salts. In a great number of factories this res- 

 idue is again taken up and boiled with a little 

 water; the solution thus obtained consists there- 

 fore chiefly of common salt, a little magnesium 

 chloride and magnesium .sulphate. Its potas- 

 sium content varies from 3 to 7 calculated 

 as potash chloride; it is used solely to dis- 

 solve fresh quantities of crude salt. The pro- 

 portions of the different solutions as well r.s 

 the densities vary with the factory. The residues 

 are thus more or less abundant and retain mere 

 or less salts. The best results are obtained by 

 preparing solutions of 32 Be. with lower den- 

 sities; they retain a large amount of common 

 salt; when on the contrary their density is higher 

 they retain less common salt and more potas- 

 sium chloride. 



The crude solution as it comes from the pan 

 is soiled with impurities; it is therefore run into 

 clarification basins, where it remains for about 

 forty-five minutes. These basins are rectangular, 

 of riveted wrought iron, fitted with two aper- 

 tures from one of which the clarified solution 

 is run off, and from the other, the sludge. To 

 prevent the clarified solution carrying the sludge 

 with it, different arrangements have been made 

 to retain it. After the clarified solution has been 

 run off, it is led through a wrought-iron gutter 



