July x t *9*8 Influence of Gypsum on Solubility of Potash in Soils 65 
In Table II are reported the amounts of soil equivalent to the solution 
used for each determination, the weight of the potassium chloroplatinate 
(K 2 PtCl 6 ), and the percentage of the potassium computed as potash 
(K^O). Duplicate determinatioifs are reported to show the degree of 
concordance. The amount of chloroplatinate in each determination was 
so large as to eliminate the large experimental errors of weighing that 
occur when only small amounts of soil are employed, while the duplicates 
in all cases are closely concordant. A blank determination was made 
with the same kind and quantities of reagents as were used in the actual 
analyses and the proper corrections made; the gypsum was analyzed and 
was found to be quite free of potash. 
In the case of each soil there is shown a marked increase, due to the 
addition of the gypsum. The greatest increase was found in the case of 
soil E in which the gain amounted to over 80 per cent and the least in 
the case of soil A 20 per cent. While the amount of gypsum employed 
in the experiment, 1 per cent, equivalent to 10 tons per acre, was much 
laq^er than is used in field practice, it would be surprising, in view of the 
results obtained, if a light application did not cause an appreciable 
increase in the water-soluble potash. 
SUMMARY 
Various Minnesota soils when mixed with 1 per cent of gypsum, raised 
to a point approximating the moisture equivalent, and kept in this condi¬ 
tion for three months showed marked increases in the content of water- 
soluble potash. 
The results in previously reported experiments by various investigators 
in which the action of gypsum has not been found to cause such an 
increase may be due to the conditions of contact between the soil and 
gypsum that they have employed being unlike those that obtain in the 
field. 
LITERATURE CITED 
(1) Alway, F. J., and McDolE, G. R. 
1917. RELATION OF THE WATER-RETAINING CAPACITY OF A SOIL TO ITS HYGRO¬ 
SCOPIC coefficient. In Jour. Agr. Research, v. 9, no. 2, p. 27-71, 4 fig. 
Literature cited, p. 70-71. 
(2) Andr£, G. 
1913. DISPLACEMENT DB LA POTASSE CONTINUE DANS CERTAINBS ROCHES FELD- 
SPATHIQUES PAR QUELQUES SUBSTANCES EMPLOYEES COMME ENGRAIS. 
In Comp, Rend. Acad. Sci. [Paris], t. 157, no. 19, p. 856-858. 
(3) Bradley, C. E. 
1910. THE REACTION OF LIME AND GYPSUM ON SOME OREGON SOILS. In Jour. 
Indus, and Engin. Chem., v. 2, no. 12, p. 529-530. 
(4) Briggs, L. J., and Breazeale, J. F. 
1917. availability of potash in certain orthoclasb-bbaring soils as 
affected BY lime or gypsum. In Jour. Agr. Research, v. 8, no. 1, 
p. 2-1-28. 
