Aug. 19,1918 Availability of Potash in Soil-Forming Minerals 
299 
Table I gives the composition of the materials used in this work. 
Table I .—Composition of materials used 
Material. 
Nitrogen 
(N).' 
Available 
phosphoric 
acid 
(p 2 o 6 ). 
Potash 
(KjO). 
Lime 
(CaO). 
Dried blood....... 
Per cent. 
J 3 - 7 ° 
Per cent. 
Per cent. 
Per cent. 
Acid phosphate. 
16. 20 
(“) 
Potassium sulphate. 
5°. 80 
8 . 45 
9.14 
13.40 
14.40 
Biotite... 
(«) 
(ct) 
Muscovite. 
Orthoclase.. 
(a) 
Microcline.. 
v 3 ) 
Precipitated calcium carbonate. 
56. 02 
a Not determined. 
The potash contents, which are very close to the theoretical for the 
individual minerals, indicate specimens of exceptional purity. Petro¬ 
graphic examinations of the feldspars give all characteristic optical prop¬ 
erties of pure orthoclase and microcline, respectively. 
solubility of mineral potash in carbonated water and the effect 
OF CALCIUM BICARBONATE THEREON 
Water charged with carbon dioxid is generally considered the chief 
solvent of inert plant nutrients of the soil. To obtain the true availa¬ 
bility of any dormant constituent, several extractions are necessary— 
that is, until a point is reached at which no appreciable amount goes 
into solution. 
Calcium bicarbonate results from the presence of any basic calcium 
compounds in the soil, and is the form of lime which naturally functions 
in the exchange of bases. 
For comparison with soil conditions, carbonated water and calcium 
'bicarbonate wefe selected for measuring the availabilty of potash in the 
four soil-forming minerals. 
Distilled water was saturated under pressure with carbon dioxid. The 
solution of calcium bicarbonate [Ca(HC 0 3 ) 2 ] was N/20 in strength, and 
contained an excess of carbon dioxid to prevent the precipitation of cal¬ 
cium carbonate (CaC0 3 ). Thirty gm. of each material and 200 cc. of 
the solvent were placed in 500-cc. flasks and agitated in an end-over-end 
slaking machine for 96 hours. At the end of this time suspended matter 
was allowed to settle, the solutions were clarified, and potash was deter¬ 
mined colormetrically, according to methods given by Schreiner and 
Failyer (1906). The residue was thrown on a filter and washed free of 
potash, after which it was again extracted as before, and the process 
repeated four times. 
The results obtained will be found in Table II. 
