the precipitation, resulting in the formation of inorganic phos- 

 phorus. 



8. Possibility of error lies in the carrying down of phosphorus 

 containing proteids with the yellow precipitate. The solution of 

 these proteids in ammonia and then precipitating with magnesium 

 mixture and the increasing of the final weight. 



The method for the separation of organic from inorganic as 

 given in the Ohio Bulletin for Plant Substances is as follows : 



Pour exactly 300 cc. of .2 per cent, hydrochloric acid on 10 grams 

 of finely ground sample in a 400 cc. flask, close with a rubber stop- 

 per and shake at intervals of five minutes for three hours. Filter 

 the extract through dry filters into dry flasks (this filtration may 

 have to be carried on by gentle suction, using a platinum cone to pre- 

 vent rupture of the paper). Measure out a 250 cc. portion of this 

 filtrate, precipitate in a 400 cc. beaker with 15 cc. of magnesium 

 mixture and 300 cc. of strong ammonia, allow to stand over night 

 and filter through a double 11 cm. 8. & S. No. 595 filter, taking- 

 care to decant as long as possible without pouring off the precipi- 

 tate. Then complete the transfer of the precipitate to the paper. 

 Suction may also help this filtration toward the end, using a plati- 

 num cone. 



The precipitate consists of magnesium ammonium phosphate with 

 Phytin, when this compound is present in the substance involved 

 and small quantities of variously colored unknowns, free nucleic 

 acid and some of their salts are soluble in ammonia and these are 

 gotten rid of. Wash several times with 2.5 per cent, ammonia and 

 then several times with 95 per cent, alcohol until free from am- 

 monia. The alcohol clears up the precipitate by dissolving out a 

 large part of the colored compounds not effecting the Phytin and 

 magnesium ammonium phosphate. The precipitate is allowed to 

 drain, and then spread out on the inner paper, allowing the alcohol 

 to evaporate. When practically dry, place the paper containing 

 the precipitate in an Erlenmeyer flask, add 100 cc. of 95 per cent, 

 alcohol containing .2 per cent nitric acid. Close the flask witli a 

 rubber stopper and shake until the paper is thoroughly broken up; 

 if the precipitate is flaky and refuses to break up on shaking allow 

 ,1o stand over night in acid alcohol. This .2 per cent, nitric acid 

 dissolves out the inorganic phosphorus but does not affect the 

 Phytin. Now filter through a dry filter into a dry flask, pipette 

 out 75 cc. of the filtrate into a small beaker, evaporate almost to 

 dryness, then determine the phosphorus in the usual gravimetric 



