Nov. 19, 1917 
Reactions of Phosphorus of Root of Turnip 
367 
acid precipitate that only two-thirds of its original phosphorus could be 
subsequently precipitated in a 2 per cent acetic-acid solution, the remain¬ 
der passing into the filtrate but still not reacting as inorganic phosphorus. 
The two-thirds of the phosphorus mentioned above as being reprecipi¬ 
tated with acetic acid were subsequently again dissolved in 0.5 per cent 
sodium hydroxid and reprecipitated with acetic acid without any fur¬ 
ther change in the amount of phosphorus in the acetic-acid precipitate. 
The reprecipitated and washed material contained about 13 parts of 
nitrogen to 1 part of phosphorus. 
An examination for phytin in turnip juice was made as follows: Two 
400-c. c. lots of turnip juice, each containing phosphorus equivalent to 
0.2272 gm. of magnesium pyrophosphate, were treated with enough 
acetic acid to make a 2 per cent solution. A precipitate containing 3 
per cent of the tot^l phosphorus was formed. The filtrate was examined 
for phosphorus in phytin according to the following method of Posternak 
(11): The solutions were made strongly alkaline with sodium hydroxid, 
and calcium chlorid was added. The white precipitate was filtered off 
and the filtrate found to contain only a trace of phosphorus. The pre¬ 
cipitate was dissolved in hydrochloric acid, and sodium acetate and 
copper acetate were added. Phytin was found to be practically absent 
(3, p- 440). 
By heating turnip juice, variable small amounts of phosphorus are 
thrown down with the not very voluminous precipitate which is formed. 
The filtrate may at once yield more or less inorganic phosphorus than an 
unheated aliquot. After the lapse of a week or more, chloroform having 
been added to the solutions, there was invariably an increase of inorganic 
phosphorus in the unheated juice and usually no increase in the heated 
juice. This indicated the possible presence of an enzym capable of in¬ 
creasing the amount of inorganic phosphorus, but efforts to prove that 
there was enzymic action were not universally successful. The amount 
of inorganic phosphorus precipitated by the immediate addition of the 
customary reagents to the juice usually constitutes so large a proportion 
of the total phosphorus that there is very little opportunity for further 
change. 
PROPORTION OF INORGANIC PHOSPHORUS 
The principle method which was used by the authors in the determi¬ 
nation of the inorganic phosphorus in fresh turnips has been published 
elsewhere (6). It consists in brief in preparing the pulp in the presence 
of sufficient acetic acid to give about a 2 per cent acid extract, to which 
barium chlorid is then added as a precipitant, the solution being ren¬ 
dered neutral or barely alkaline with ammonium hydroxid. The inor¬ 
ganic phosphate is dissolved on the filter from the precipitate by treat¬ 
ment with hot water and acid, and the phosphorus brought into solution 
is determined in the usual manner with molybdenum and magnesium 
mixtures. 
