450 



SOILS. 



and later with Jaffa, investigated it quantitatively. 1 It was found that 

 up to .75 grms. per liter, the entire amount of sodic sulfate present in 

 solution is transformed into carbonate in presence of calcic carbonate, 

 by a current of carbonic dioxid ; but the amount so transformed does 

 not continue to increase beyond about 4 grams per liter. A correspond- 

 ing amount of calcic sulfate is formed. In the case of potassic 

 sulfate, the transformation also occurs, proportionally to the molecular 

 weight. This relation is shown in the subjoined diagram, which also 

 shows in the curves on the left, the residual alkalinity left after evapora- 

 tion and drying the residue at 100 C. 



01 234567 



Grams per Efter KHCO S 

 9 10 11 12 13 U 15 16 17 18 19 20 21 22 23 24 25 29 



FIG. 6g. Progressive Transformation of Alkali Sulfates into Carbonates. (The figures along 

 upper line represent tenths of one per cent.) 



The corresponding reaction occurs also, of course, between 

 sodium chlorid and calcium carbonate, but not to the same 

 extent, because unlike the difficultly soluble gypsum, the reac- 

 tion product is the very soluble calcium chlorid, the presence of 

 which in the solution limits the reaction much sooner than 

 when most of the decomposition product is thrown down in 



1 Proc. Am. Soc. Agr. Sci., 1888 ; ibid., 1890; Rep. Cal. Expt. Sta., 1890, p. 100; 

 Ber. Berlin, Chem. Ges., 1893; Am. Jour. Sci., August 1896. 



