146 Adenine and Guanine 
EXPERIMENTAL. 
The milk was obtained from a herd of Jersey cows and repre- 
sented a mixed sample. 100 liters of milk were worked up in 
the following manner: The whole milk, after a thorough shak- 
ing, was made slightly acid with acetic acid. The curdled milk 
was then filtered by suction. To the filtrate an equal volume of 
95 per cent alcohol was added and again filtered. This seemed 
to remove most of the remaining protein and a clear transparent 
liquid was the result of this last operation. The addition of the 
alcohol also served a second purpose. As the fluid had to be 
evaporated to a very smalJl volume in vacuo, the addition of alco- 
hol lowered the boiling point of the solution, thus preventing over- 
heating. After evaporating the solution at 45°C. in vacuo to 
about 5 per cent of its original volume a thick white liquid 
remained. This residue contained fats, milk sugar, lipoids, 
traces of protein, as well as inorganic salts. The fats and lipoids 
were removed by repeated extraction with ether, and the protein 
was removed by a single filtration. The remaining liquid was 
acid in reaction (acetic), yellowish green in color, and had a 
syrupy consistency. After standing for 24 to 48 hours, crystals 
began to appear and after about 2 weeks (depending on concen- 
tration) the crystallization became complete. The crystals. were 
lactose. For the sake of convenience 8 liters of milk were worked 
up in this manner daily. The final volume of each lot of milk 
amounted to from 350 to 400 cc. The various portions were 
united and treated with a concentrated aqueous solution of either 
silver acetate or nitrate. “One-fourth of the entire solution 
(1,500 cc.) was thus treated with Ag acetate in excess. The re- 
mainder was precipitated with an excess of silver nitrate. The 
precipitate caused by the addition of the silver solutions to the 
milk residue was necessarily divided into two lots; silver purine 
precipitate from AgNO; and silver purine precipitate from silver 
acetate. Both precipitates were filtered off separately and washed 
well with cold water. , 
Treatment of Silver Purine Fraction. 
The AgNO; purine precipitate was washed off the filter, sus- 
pended in water, to which sufficient HCl had been added to 
