260 REPORT OF THE CHEMIST OF THE 
tically base-free. Preparations made by coagulating cows’ milk 
with rennet and washing the coagulum are high in ash content, 
containing often 4 or 5 per ct.; moreover, such preparations still 
contain the calcium originally combined in the calcium casein of 
the milk and are not satisfactory for such work as we desired 
to do. We therefore made a preparation of paracasein as fol- 
lows: 
Preparation of paracasein.—-To one liter of skim-milk, we added 
1.25 grams of ammonium oxalate; the milk, after standing a 
short time, was filtered through paper. To 500 ce. of this fil- 
trate we added .05 cc. of Hansen’s rennet extract and kept the 
whole at a temperature of 37° ©. for two hours. A small amount 
of thymol was added. To show that the rennet enzym had acted 
upon the calcium casein in the milk, we took 10 cc. of the treated 
milk, cooled to room temperature, and added two drops of a 10 
per ct. solution of calcium chloride. In a few minutes the milk 
had formed a firm coagulum, which indicated that the rennet 
enzym had functioned and produced paracasein. The 500 cc. of 
treated milk we now diluted with 16 liters of warm, distilled 
water and added dilute hydrochloric acid until the proteid had 
separated. This precipitation was accompanied by vigorous stir- 
ring to keep the proteid as finely divided as possible, thus facili- 
tating the removal of inorganic salts. After the precipitate had 
settled, the supernatant liquid was removed, the precipitate was 
filtered and then triturated with warm water and filtered, the 
trituration and filtering being repeated until all trace of chlo- 
rides was removed, which required four days. The precipitate 
after removal of acid was soluble in warm 5 per ect. salt solu- 
tion and in hot 50 per ct. alcohol. Finally, the preparation 
was washed with strong alcohol and ether and dried at 100° C. 
This treatment greatly lessened its solubility in dilute salt solu- 
tion and alcohol. It was nearly ash-free, containing 0.11 per 
ct. and gave no test for chorides when boiled with nitric acid and 
silver nitrate. ; 
Solubility of paracasein nreparation in lime-water.—The para- 
‘asein, prepared in the manner described, was soluble in lime- 
waiter, forming a solution having a dull, opalescent appear- 
ance. 
