Pkoceedings of Seventeenth Normal Institute 135 



sient crushers are sometimes available after the mamier of wheat 

 threshers. But, iu some cases of isolation and long, difficult haul, 

 common sense dictates the use of the most concentrated form of 

 lime ; that is, burnt lime, in preference to limestone. 



In more recent years the commercial basis of comparison be- 

 tween ground limestone and burnt lime has undergone consider- 

 able change, because of the marked development in moderate 

 priced portable crushers, which give a large tonnage per diem of 

 very finely ground limestone. Then, too, some extensive indus- 

 tries, such as the production of zinc, have made available, in some 

 communities, large quantities of cheap, by-product limerock. How- 

 ever, even the finest pulverized limestone is not comparable in 

 fineness with the carbonate of lime which is formed from burnt 

 or hydrated lime in soils. But, be it emphasized, fineness governs 

 solubility. An apt parallel may be drawn, for purposes of com- 

 parison, between availability of equal amounts of CaO as oxid or 

 hydrate after carbonation, as compared with finely ground lime- 

 stone, and the availability of equal amounts of phosphoric acid in 

 the form of acid phosphate and finely gi'ound phosphate rock. It 

 is generally held that, under favorable soil conditions with refer- 

 ence to lime, the ultimate product to be found in the soil subse- 

 quent to application of acid phosphate is identical chemically 

 with finely ground raw phosphate rock. However, as we know, 

 there is a vast difference between the availability of these two 

 physical forms of the same chemical product. In other words, 

 degi'ee of fineness determines the chemical activities, the rate of 

 solution, and hence availability to the growing plant. 



The following table will give some idea of the influence of fine- 

 ness upon solubility. The data were secured from separates of 

 the same sample of New York limestone and compared with car- 

 bonated burnt lime. 



Table I. 



SOLUBILITY OF CaCOs IN CARBONATED WATER AS INFLUENCED BY DEGREE OF 



FINENESS. 



Solubilitj/ 

 Size of CaCOz coefficient 



Greater than 10 mesh 1 • 



10 mesh — 50 mesh 2.2 



50 mesh — 100 mesh 6.2 



100 mesh — 200 mesh 8.0 



Less than 200 mesh 14.8 



Carbonate from burnt lime 28 . 



