118 Report oF THE CHEMIST OF THE 
potato. He also isolated and identified the free acid as anhydro- 
oxymethylene diphosphoric acid with the following formula: 
Weel 
Cie eres Ten 
td 
NOH ANG PD Tony 
me 
pi 5s 
The method adopted by Posternak was the following: 
The material was extracted with dilute hydrochloric acid and 
filtered, the filtrate was made alkaline with sodium hydrate and 
precipitated with calcium chloride. The calcium chloride pre- 
cipitate was filtered, washed and finally dissolved in dilute hydro- 
chloric acid. Sodium acetate was added to the solution to 
replace the free mineral acid by acetic acid, and copper acetate 
added in excess. The copper precipitate was filtered, thoroughly 
washed with water and decomposed by hydrogen sulphide. _ 
The copper sulphide was removed by filtration and the excess 
of hydrogen sulphide removed by pumping air through the 
liquid. It was then evaporated in a vacuum over sulphuric acid. 
We found it very difficult to remove the last traces of calcium 
by this method and have modified it by substituting barium chlo- 
ride for calcium chloride. This admits of a very thorough wash- 
ing at this stage of the operation as the barium salt is much more 
insoluble than the calcium salt and also admits of a complete 
removal of the barium as a sulphate. 
o 
METHOD OF PREPARATION OF FREE ACID. 
The method finally adopted by us is as follows: 
The bran was extracted with 0.2 per ct. hydrochloric acid, 
strained through cheese cloth and filtered through paper. Since 
the compound is present in bran as a calcium-magnesium-potas- 
sium salt, it was precipitated directly with copper acetate, by 
which means we were able to remove the greater part of these 
bases. After washing the copper precipitate it was suspended in 
water and decomposed by hydrogen sulphide. The filtrate from 
copper sulphide was made alkaline with sodium hydrate and pre- 
