Nov. 19, 1917 
Reactions of Phosphorus of Root of Turnip 
365 
might still be considered as inorganic phosphorus which would combine 
readily with the usual precipitants of the same. 
Realizing the indefiniteness of so-called inorganic phosphorus in such 
circumstances, the authors did not attempt to determine definitely the 
nature of the phosphorus precipitable by different reagents, because 
the main object was to find methods for determining differences in com¬ 
position in turnips grown on soils containing different amounts of avail¬ 
able phosphorus. In general the designation 4 4 inorganic phosphorus * , has 
been used in the present paper more for convenience than because it is 
necessarily considered as representing a well-defined entity. 
It was found that the Hart and Andrews method (2), as outlined 
for use with cereals, required with turnip extract so much nitric acid 
to prevent reduction in the molybdenum mixture and to enable a com¬ 
plete recovery of added phosphorus that the official strength of nitric 
acid was adopted in most cases with this reagent. 
Many direct precipitations were made also with the official magnesium 
mixture. The comparative amounts of that portion of the phosphorus 
which was precipitated directly by the magnesium and by the molybde¬ 
num mixtures, from different lots of turnip juice, are shown by the fol¬ 
lowing: If the amount precipitated with the magnesium mixture in each 
case is represented by 100, the amounts thrown down by the molybdenum 
mixture were 100, 93, 99, 95, 102, 95, and 98; average, 97. The two 
mixtures therefore gave practically the same results. The precipitates 
caused by the two reagents were so treated that the total phosphorus in 
them was determined. 
Barium chlorid in neutral solutions was also used extensively as a 
precipitant; in fact, it was finally adopted as being in general the most 
suitable reagent. 
The best criterion of the efficiency of the different methods for pre¬ 
cipitating inorganic phosphorus in the presence of the colloidal organic 
constituents of turnip extract was considered to be the degree of recovery 
of phosphorus added in a standard solution to the dialyzates of the tur¬ 
nip extracts, from which practically all the phosphorus had diffused. 
Evidence presented in regard to the correctness of a given method for 
determining inorganic phosphorus is of questionable value if it is based 
upon the extent to which phosphorus added in a standard solution is re¬ 
covered from an extract in which inorganic phosphorus had been deter¬ 
mined previously by the same method. 
At first there was failure by any of the precipitants to precipitate 
completely the phosphorus added to the dialyzate, but as barium chlorid 
seemed the most promising the conditions for practically complete re¬ 
covery were ascertained finally with this reagent. It was not deter¬ 
mined whether or not conditions could have been imposed in connection 
with the molybdenum and magnesium mixtures which would lead to a 
