POTASSIC MANURES 121 



potassium and chlorine, but only a small trace of 

 each was found. 



That shows that the volatilization of the potash 

 in feldspar takes place more rapidly when part 

 of the lime is replaced by calcium chloride than 

 when feldspar is ignited with it alone, but in 

 each case the ultimate composition of the residue 

 obtained is the same. Any excess of calcium 

 chloride used above that equivalent to the potas- 

 sium in the feldspar is slowly decomposed at the 

 temperature at which the ignitions were made, 

 leaving behind the oxide of calcium. 



Since the clay used in making cement contains 

 in some cases as high as 3 or 4 per cent of potash, 

 it might be expected that part would escape from 

 the kiln and be collected with the flue dust 

 (particularly in those plants where a process for 

 collecting dust has been installed: This has been 

 observed by several investigators to really take 

 place), and the potash then collected is found to 

 be in a soluble form. By the substitution of 

 feldspar for clay in the manufacture of cement, 

 the potash then collected would, no doubt, be 

 greatly increased, but since the analyses of cement 

 show the presence of alkalies, it follows that with 

 the style of kilns now in use all the potash in 

 feldspar could not be made available in this way, 

 and that a larger proportion of the potassium 

 would be volatilized by substituting for a part 

 of the lime, sufficient calcium chloride to be 

 equivalent to the potassium, is evident from the 



