366 
Journal of Agricultural Research 
Vol. XI, No. 8 
complete recovery of added phosphorus, but such seemed probable from 
the results of the limited attempts which were made. 
In preliminary work with undialyzed turnip juice and a standard 
phosphate solution containing phosphorus equivalent to 0.0200 gm. of 
magnesium pyrophosphate, there was obtained by barium chlorid from 
a neutral solution in 4, 8, 16, 24, and 72 hours, respectively, 0.0120, 
0.0186, 0.0194, 0.0200, and 0.0200 gm. more than was secured from the 
juice alone. This indicated that 24 hours was sufficient time for complete 
precipitation. It was also ascertained that a large excess of the reagent 
was of no advantage. 
Based upon this preliminary work, added phospnorus was recovered 
completely a number of times from dialyzates of turnip juice from 
which practically all of the phosphorus had diffused. However, owing 
to the fact that in a few instances thare was failure to recover all of the 
added phosphorus, it seems probable that a minus error is liable to occur 
when precipitating with barium chlorid from a strictly neutral solution, 
and it is probable that the method is more dependable if the solution is 
made slightly alkaline with ammonium hydroxid. A more detailed dis¬ 
cussion of the method will occur in subsequent pages. 
A limited amount of work was done with promising results by the 
method outlined by Collison (1), but the barium-chlorid method seemed 
well adapted for the work with turnip juice and was therefore 
mainly used. 
ACTION OF OTHER REAGENTS AND CHANGES EFFECTED IN 
DIFFERENT WAYS 
Although primarily interested in the determination of so-called inor¬ 
ganic phosphorus, the authors made certain examinations of turnip 
extract to ascertain the behavior of the phosphorus under different con¬ 
ditions, and these will be referred to briefly at this time. 
Turnip juice is not of constant composition, but as an average less 
than one-tenth of the phosphorus in it is precipitated by acetic acid, 
more than seven-tenths by barium chlorid subsequently in the neutral¬ 
ized filtrate, and about two-tenths remain in the filtrate from the barium- 
chlorid precipitate. 
The following data throw light upon the nature of the acetic-acid pre¬ 
cipitate: Acetic acid was added to 1,500 c. c. of fresh juice until the 
acidity equalled 2 per cent; the mixture was allowed to stand for four 
days and was then filtered. The precipitate, after washing with 2 per 
cent acetic acid, was digested in a beaker for one hour at 37 0 C., with a 
solution of sodium hydroxid containing 0.5 per cent of free alkali. No 
reaction for inorganic phosphorus was secured when molybdenum mix¬ 
ture was added to the solution, thereby indicating that the phosphorus 
of the acetic-acid precipitate was not in compounds of a phosphoprotein 
nature (10). The alkaline digestion, however, so changed the acetic- 
