CH. III.] 



GUANINE AND ADENINE. 



65 



If a portion does not filter well after being boiled and dried on a paper 

 heated with boiling water, the point must be reached by the addition 

 of more acetic acid or of caustic soda. Now boil the bulk and filter, 

 using a hot water funnel. Concentrate the filtrate on a water bath to 

 about 750 cc., and pour the warm solution slowly into I litre of 95 

 per cent, alcohol in a large beaker. Allow the mixture to stand over- 

 night. The precipitated sodium nucleate settles to a spongy 

 white mass. Pour off the .supernatent fluid and squeeze out the 

 remainder as far as possible by means of a spatula. Wash by 

 decantation first with 80 per cent., and then with 95 per cent. 

 alcohol. Squeeze out the last wash fluid as much as possible and 

 transfer to a flask with 300 cc. of hot water, and heat on the water 

 bath for 30 minutes. Add 10 cc. of 20 per cent, caustic soda, and 

 filter from insoluble phosphates, using a hot water funnel. Acidify 

 with acetic acid and pour into 700 cc. of 95 per cent, alcohol. Allow 

 to stand over-night, wash by decantation with alcohol of increasing 

 strength, and grind in a mortar with absolute alcohol until it has 

 crumbled into a fine white powder. Transfer to a filter with absolute 

 alcohol and dry in a sulphuric acid desiccator. The product should 

 weigh over 30 grms., and consists of the soluble sodium salt of 

 thymus nucleic acid. 



A 4 to 5 per cent, solution in warm water becomes gelatinous at 

 room temperature, the viscosity being decreased both by acetic 

 acid and sodium hydroxide. 



77. Preparation of Guanine and Adenine from Nucleic Acid. 



Heat on a boiling water bath 50 grams, of commercial yeast nucleic 

 acid for two hours with 200 cc. of 10 per cent, sulphuric acid in a 

 flask fitted with a reflux condenser. Treat the hot fluid with strong 

 ammonia. Guanine is precipitated. Continue to add the ammonia 

 till the neutral point is reached, and then add an excess of 2 per cent, 

 of the reagent. Allow to cool and filter. Reserve the filtrate A. 

 Wash the guanine with i per cent, ammonia, adding the washings to 

 A. Suspend the guanine in boiling water and dissolve in a minimal 

 amount of 20 per cent, sulphuric acid. Add a small amount of 

 good charcoal, boil, and filter. Add ammonia as before to precipi- 

 tate the guanine. Filter, dry at 40 C., and dissolve in 20 to 25 

 times its weight of boiling 5 per cent, hydrochloric acid. Upon 



