Scientific Proceedings. 



7i 



to act for periods of varying length on pure preparations of the 

 compounds. 



In the observations of which the present paper is the result, 

 nucleic acid from yeast and Hammarsten's nucleoproteid of the 

 pancreas were employed as representatives of the true nucleopro- 

 teids while caseinogen exemplified the para compounds. 



The yeast nucleic acid and the pancreatic nucleoproteid were 

 prepared in such a way as to free them from lecithin and inorganic 

 phosphates. The nucleic acid was dissolved in dilute sodic hydrate 

 solution (1 per cent, strength) and precipitated therefrom with 

 dilute hydrochloric acid. This solution and precipitation was 

 repeated three times. The precipitate was finally extracted with 

 ether in a Soxhlet apparatus to remove all traces of lecithin. The 

 pancreatic nucleoproteid was prepared by extracting the minced 

 pancreas with boiling water, filtering and adding to the filtrate 

 dilute acetic acid, when the nucleoproteid was precipitated. The 

 precipitate was carefully washed with very dilute acetic acid solu- 

 tion, then dissolved in very dilute ammonium hydrate and the 

 solution rendered acid with acetic acid. The precipitate so obtained 

 was again carefully washed, dissolved and once more precipitated. 

 It was then extracted with ether to remove all traces of lecithin. 



In order to determine the absence of phosphates portions of 

 the nucleic acid and of the nucleoproteid so obtained were treated 

 with a solution of ammonium molybdate in nitric acid prepared 

 according to Fresenius' method and the addition of the reagent 

 was followed immediately by that of a solution of phenylhydrazin 

 of 2 per cent, strength. This gave no change of color, indicating 

 the total absence of phosphates. As the nitric-molybdate reagent 

 when employed with phenylhydrazin solution shows one part of 

 P in 2,600,000, the test is an exceedingly sensitive one and con- 

 sequently it may be relied on to indicate whether phosphates are 

 wholly absent. 



When, however, nitric acid of 30 per cent, strength was allowed 

 to act on portions of either the nucleic acid or nucleoproteid for 

 twenty four hours at 35°C.,the addition of the nitric-molybdate 

 reagent at once produced a precipitate which is immediately re- 

 duced to green or greenish-blue on the addition of the phenyl- 

 hydrazin solution. That the yellowish precipitate is molybdo- 



