vem Report oF THE CHEmMIOAL DEPARIMENT OF THE 
PREPARATION OF CHEESE EXTRACT. 
Twenty-five grams of cheese are mixed with quartz sand and 
treated at 122° to 140° F. (50° to 60° C.) for a half hour with 
each of several successive portions of water, decanting and 
filtering each portion of extract until 500 cc. have been accummu- 
lated. Portions of the solution thus prepared are used in 
making the various determinations. 
DETERMINATION OF NITROGEN-COMPOUNDS IN CHEESE EXTRACTS. 
(a) Total water-soluble nitrogen is determined in an aliquot part 
of the water extract. 
(b) Precipitation by alum.—To 100 cc. of water extract, 2 ce. 
of saturated alum solution are added and digested at 104° to 
108° F. (40° to 42° C.) until precipitation is complete. The 
precipitate is filtered, washed and then treated by Kjeldahl 
method to determine nitrogen. 
(c) Coagulation by neutralizing and boiling—The clear filtrate 
from (b) is exactly neutralized by dilute fixed alkali and heated 
on water bath until coagulation is complete. The precipitate is 
filtered, washed and its nitrogen determined by Kjeldahl 
method. 
(d) Albwmoses.—To the filtrate from (c) two or three drops of 
dilute (one to three) sulphuric acid are added, and then powdered 
zinc sulphate to saturation. The mixture is heated on water 
bath until precipitation is complete and the nitrogen is deter- 
mined in the precipitate washed with saturated solution of zine 
sulphate. 
(ec) Peptones.—To the filtrate of (d) two or three drops of 
“strong hydrochloric acid are added and then bromine in succes- 
sive portions of a few drops at a time, accompanied by vigorous 
shaking until the liquid becomes super-saturated. The nitrogen 
in the washed precipitate is determined as before. 
(f) Amides.—(1) First Method. ‘The nitrogen in filtrate from 
(e) is determined directly by Kjeldahl method and this, less the 
nitrogen present as ammonia, is the amide nitrogen. ! 
(2) Second Method. To 100 cc. of the original cheese extract — 
