360 
Journal of Agricultural Research 
Vol. XI, No. S 
the phosphorus determined after ignition with magnesium nitrate, as has 
usually been done in connection with determining total phosphorus. 
The residue from the ether-alcohol extraction was treated successively at 
room temperature with five portions of 0.2 per cent hydrochloric acid. 
Each portion was allowed to stand at least 24 hours, with frequent 
stirring. In this extract was determined, in separate aliquots, the 
total phosphorus, that which was precipitated directly by molybdenum 
mixture according to the method used by Hart and Andrews (2) for 
determining “inorganic” phosphorus, as well as that precipitated by 
alcohol. The amount of phosphorus in the residue from the extractions 
was likewise determined. The results are given in Table I. 
Table I .—Percentage of phosphorus pentoxid in dry flat turnips 
Fractional solubilities expressed as per¬ 
centages of total phosphorus pentoxid— 
Flat turnips— 
Per¬ 
cent¬ 
age of 
In 0.2 per cent 
hydrochloric 
acid. 
Resi¬ 
phos¬ 
phorus 
pent¬ 
oxid. 
In 
ether 
and 
alcohol. 
Pre¬ 
cipi¬ 
tated 
by 
molyb¬ 
denum 
mix¬ 
ture. 
Pre¬ 
cipi¬ 
tated 
by 
alcohol. 
due 
from 
preced¬ 
ing 
sol¬ 
vents. 
Total. 
From soil unmanured with phosphorus. 
O. 45 
13 
55 
16 
16 
100 
From the same soil manured with an insol¬ 
uble phosphate. 
*45 
II 
48 
20 
21 
100 
From the same soil manured with bone. 
.87 
9 
73 
II 
7 
100 
From soil containing very little available 
phosphorus. 
.27 
10 
53 
20 
17 
100 
From soil containing a medium amount of 
available phosphorus. 
. 60 
11 
59 
9 
21 
100 
From soil containing much available phos¬ 
phorus . 
1. 14 
10 
66 
8 
16 
100 
It may be noticed, in case of the hydrochloric-acid extract of the 
turnips referred to, that larger proportions of phosphorus precipitated 
directly by molybdenum mixture are exhibited in the third column of 
the table (73 and 66 per cent) than in the others. These samples were 
grown in soils well supplied with available phosphorus, and the suggestion 
was thus received that possibly a plentiful amount of available phos¬ 
phorus in the soil results in an increased proportion of that part of the 
phosphorus which has sometimes been classed as inorganic. The work 
of Koch and Reed (9), which included the growing of Aspergillus niger in 
nutrient solutions containing a very small as well as increasing amounts 
of phosphorus, was published at the time the preliminary work was going 
on and was of interest in the same connection. They found that the 
ratio of the protein phosphorus to the water-soluble or extractive phos- 
