40 



Prof. W. B. Bottomley. The Isolation from 



evidently impure, for on solution and reprecipitation much of the colouring 

 matter was removed. 



This method was found to be laborious when working with such a 

 substance as peat, owing to the large amount of humic acid brought into 

 solution by the caustic alkali employed, and the difficulty of rapidly removing 

 this after precipitation. 



After numerous experiments it was found that when peat is extracted 

 with a solution of sodium bicarbonate the humic acid remains undissolved, 

 and there is separated from the filtrate a product similar to that obtained by 

 extraction with caustic soda. 



Accordingly, a quantity of finely rground air-dried raw peat was saturated 

 with a 1-per-cent. solution of sodium bicarbonate, and allowed to stand for 

 24 hours. The liquid was then expressed, and the peat again extracted with 

 a similar solution. The combined extracts were filtered, just neutralised 

 with hydrochloric acid, concentrated in vacuo to a small volume, and then 

 poured into about four volumes of absolute alcohol containing sodium acetate 

 and hydrochloric acid. The flocculent precipitate was allowed to settle for 

 24 hours, and after decanting the supernatant liquid through a filter, the 

 precipitate was washed and dried in a vacuum desiccator. The combined 

 filtrate and washings were preserved for examination. 



Uxamination of the Frecipitate. 



From the method of preparation, the substance obtained was thought to be 

 nucleic acid, and on incineration of a portion a considerable amount of 

 phosphoric acid was obtained from the ash. Mild hydrolysis with mineral 

 acids, however, failed to yield more than a trace of a purine base, but the 

 hydrolysed product reduced Fehling's solution and gave Molisch's reaction 

 for carbohydrates. The failure to obtain definite purine substances indicated 

 that the product was not similar in nature to yeast nucleic acid, which 

 readily yields purine bases on mild hydrolysis with mineral acids. An 

 examination of the alcoholic filtrate showed that it also contained phosphoric 

 acid, sugar, and a purine base. 



As this mild hydrolysis failed to yield an appreciable quantity of purine 

 bases, although the substance was highly nitrogenous, the method of stronger 

 hydrolysis described by Jones* for obtaining pyrimidine derivatives was 

 employed. This method also separates the purine bases, if present, as a 

 silver compound. 



(a) Separation of Purine and Pyrimidine Bases. — Twenty grammes of the 

 substance were heated with 150 c.c. of 25-per-cent. sulphuric acid in an 

 * Jones, W. 'Nucleic Acids,' p. 90 (1914). 



