The Soil. 
29 
this was less than one quarter of a millimeter in diameter. The 
mechanical analyses of the soils show that 60 per cent, of the soil 
particles are smaller than one fourth of a millimeter in diameter. 
This feldspar used had been washed out of the soil and was treated 
just as the soil was, and the results were as follows: Potash dis¬ 
solved out of the feldspar by digesting with hydrochloric acid, sp. 
gr. 1.115, for five days, was 0.845 per cent.; soda, 0.816 per cent.; 
silicic acid set free, 4.31 per cent. This simple experiment is so de¬ 
cisive of the fact that five days digestion with dilute hydrochloric 
acid, sp. gr. 1.115, will extract potash from finely divided orthoclase 
in considerable quantities, that further questions arise as to whether 
plants can use the potash present in this form, or is our analysis of 
such a soil wholly misleading ? The following questions are also 
suggested, viz : To what extent does water alone act on this min¬ 
eral, for that water extracts potash from it is already an established 
fact, and how much does carbonic acid increase its solvent action ? 
ACTION OF WATER AND CARBONIC ACID ON FELDSPAR. 
§ 57. The perfectly fresh, finely pulverized feldspar was 
suspended in water, 10 grams in 300 c. c., and allowed to stand five 
days with frequent shaking. One hundred c. c. of this solution was 
filtered off, evaporated to dryness, and the residue weighed. An¬ 
other portion of feldspar was treated in the same manner, except 
that the water was saturated with carbonic oxid. 
§ 58. A like quantity of water was placed beside these and 
carried through as a control. 
§ 59. The water dissolved from the feldspar 0.0081 gram, 
after deducting the amount contained in the distilled water. 
§ 60. The water charged with carbonic oxid dissolved 0.0723 
gram. The residue obtained in this case gave a heavy precipitate 
for potash with platinic chlorid, as did the water solution of the 
feldspar. The residue from the distilled water did not react for 
potash. 
EXPERIMENTS WITH OATS. 
§ 61. This question was carried still further, and we en¬ 
deavored to determine whether the feldspar could furnish potash to 
plants. For this purpose the perfectly fresh mineral was used, pul¬ 
verized as already described in imitation of the soil, i. e., the parti¬ 
cles varied from one millimeter in diameter to an impalpable pow¬ 
der. This was mixed with pure quartz sand. Bone ash was used 
to supply lime and phosphoric acid. The sample used contained 
no potash. Nitrate of lime furnished the nitrogen. Chlorin was 
furnished by a minute quantity of calcic chloride. Distilled water 
was used throughout the experiment. 
The plants grew healthily in this mixture until the floors of the 
