A Study of Colorado Wheat 
125 
The only objection against the use of silica dishes was the fact that 
small flakes sometimes broke loose and were weighed as silica. The amount 
of silica this adds to that of the wheat is extremely small and is usually 
negligible. 
The iron, calcium and magnesium were precipitated as phosphates. 
The iron was weighed as phosphate, the calcium as oxid and the magnesium 
as pyrophosphate. 
The alkalis remained in the filtrate from the precipitate of the phos¬ 
phates of iron, lime and magnesia. The filtrate was concentrated, and if 
still alkaline, was acidulated with hydrochloric acid. An excess of ferric 
chlorid was added and then ammonia in excess to throw down the ferric 
oxid and with it the phosphoric acid. The precipitate was filtered off, 
washed, dissolved in hydrochloric acid and reprecipitated. The united fil¬ 
trates contain the alkalis as chlorids. The procedure from this on was as 
usual. 
The calcic oxid obtained in the above manner is always slightly brown, 
due to the presence of manganese. It is very probable that the magnesia 
is also always contaminated in a slight degree. 
The chlorin was determined in a separate portion of 10 grams or more. 
The portion of wheat taken was dissolved in a mixture of nitric acid 
and argentic nitrate. When the wheat was completely dissolved and only 
a white flocculent precipitate remained, water was added, which materially 
increased the precipitate. This precipitate contained the whole of the chlorin 
as silver chlorid or otherwise. It was filtered off, washed in part (wash¬ 
ing is not necessary when sucked sufficiently dry by the pump), the mass 
impregnated with a mixture of potassic nitrate and sodic carbonate, trans- 
fered while still moist to a nickel dish containing two or three grams of the 
deflagrating mixture on which the fully opened filter was placed, covered 
lightly with the mixture and the whole heated until the mass was com¬ 
pletely fused. The amount of the deflagrating mixture used was from 
five to seven grams. The fused mass was dissolved in water and the usual 
method for the determination of chlorin followed. The fusion is so quickly 
made that chlorin, if present in the gas, can cause no appreciable error in 
the results. 
The phosphorus was also determined in a separate ten-gram portion. 
The wheat was dissolved in concentrated nitric acid and one and a half 
grams of magnesic oxid added. The whole was evaporated to a brown gummy 
mass and ignited. The amount of magnesia added is not sufficient to cause 
the complete combustion of the organic matter, but the mass bums without 
deflagration. The cooled and partly white mass was treated with dilute 
nitric acid, or wet with water, and concentrated acid added, evaporated 
again, and the combustion completed. The magnesic oxid containing the 
phosphate was dissolved in nitric acid and evaporated with sulfuric acid 
to separate silicic acid and the phosphoric acid precipitated as molybdate, 
and finally weighed as magnesic pyrophosphate. 
