6 



author of the patent covering this process, who only claimed an ex- 

 traction of about 41 per cent of the potash in- the -feldspar when 

 using the proportion of the reagents stated in the patent, viz, 1 

 part feldspar, 1 part lime equal to 1.8 parts calcium carbonate, and 

 0.2 part sodium chloride. It was pointed out, however, that a more 

 favorable result was obtained by using a larger amount of salt with 

 a smaller amount of lime. Thus, when 100 parts of feldspar were 

 ignited to 900 C., with 40 parts of lime and 40 parts of salt, about 

 70 per cent of .the potash in the feldspar became soluble, which agrees 

 with the value given in the table for approximately this proportion 

 of the reagents. 



Unless a large excess of calcium chloride is used, when ignited 

 with feldspar and lime, no vitrification takes place on heating to a 

 temperature up to 1,050 C. The ignited mass remains in the form 

 of a powder, and consequently the soluble material present can be 

 readily leached out without the necessity of any previous grinding 

 of the mass. The same statements hold true when sodium chloride is 

 used, but with a more limited variation in the proportions of the re- 

 agents which may be taken. Thus, a hardened mass is obtained when 

 1 part of feldspar is ignited to 1,050 C., with 1 part of calcium car- 

 bonate and 0.25 part of sodium chloride, but if the proportion of 

 calcium carbonate is doubled the mass remains in a powdered form. 

 When calcium chloride is used, the mass does not harden on ignition, 

 even with 1 part of calcium carbonate. 



On account of its simplicity, the method of decomposing feldspar 

 by heating with calcium carbonate and with calcium chloride (or 

 sodium chloride) could undoubtedly be carried out on a large scale 

 without involving any serious mechanical difficulty, and the method 

 would thus be a practical one providing the value of the products 

 obtained would compensate for the expense involved. Although 

 pure feldspar may be obtained which contains upward of 15 per 

 cent potash, the average grade of feldspar which could be mined on 

 a large scale would undoubtedly contain less than 10 per cent. If 

 potash be quoted at 66 cents a unit, 1 then the potash in a ton of 

 feldspar containing even 10 per cent of this constituent would be 

 worth only $6.60 when converted into a soluble form. It is thus evi- 

 dent that the value of the potash alone will not compensate for its 

 extraction by this process, or by any modifications of it for which pat- 

 ents have been granted; nor is it at all likely in view of the com- 

 paratively low percentage of potash in all silicate rocks that any 

 process can be devised which will prove so simple that the value of 

 the potash alone will pay for its extraction. It seems safe to say, 

 therefore, that any method to be economical must produce at the same 

 time other products of value in addition to the potassium. 



1 Estimated from prices quoted by the German Kali Works. 

 [Cir. 71] 



