New York AGRICULTURAL EXPERIMENT STATION. 199 
or more for complete filtration of 500 cc. of extract. Several 
samples of cheese can be extracted at the same time. The 
upper layer of cotton holds all solid particles and can be re- 
turned to the flask for extraction with salt-solution. 
The method of making a water-extract of cheese, as de- 
scrihed above, insures the complete removal of all water-soluble 
nitrogen compounds present in the cheese without danger of 
coagulating any soluble proteids. The use of water at room 
temperatures is not, in our experience, equally effective in 
making a complete extraction of the water-soluble products. 
Under some conditions, as in the early stages of ripening cheese 
at low temperatures, small amounts of a body are extracted 
by water which is precipitated by heat in neutral solution. 
We are unable to say at present whether this body consists 
of acid salts of paracasein or of hetero-caseose, which are prac: 
tically insoluble in water, or whether it is some other com- 
pound. The temperature 122° F. (50° C.) also has the advant- 
age of arresting further peptic or trypic action during the ex- 
traction. The use of acids in extracting cheese is to be avoided, 
since a small amount of acid will not only precipitate the solu- 
ble nuclein but may form salts with paracasein, which are 
somewhat soluble in a slightly acid solution; the amount of 
dissolved paracasein salts under such circumstances depends 
on the amount of acid used and the time of extraction. 
4. DETERMINATION OF TOTAL WATER-SOLUBLE NITROGEN. 
For the determination of the amount of total water-soluble 
nitrogen, we take 50 ce. of the water-extract, prepared as 
described above, equivalent to 2.5 grams of cheese, and treat 
it according to the Kjeldahl method for determining nitrogen. 
5. DETERMINATION OF NITROGEN IN THE FORM OF PARANUCLEIN 
(PSHEUDONUCLEIN. ) 
To 100 ce. of the water-extract, equivalent to 5 grams of cheese, 
we add 5 ce. of a 1 per ct. solution of hydrochloric acid, and 
warm the mixture on the water-bath at 122° F. to 131° F. (50° C. 
to 55° C), until complete separation takes place, as shown by a 
