214 Report OF THE CHEMIST OF THE 
a flocculent precipitate separates, leaving a clear supernatant 
liquid. Filter, wash and treat by the Kjeldahl method for esti- 
mating nitrogen. 
In fresh milk, 2 or 3 ce. of a saturatedsvlution of alum may be 
used in place of acetic acid, usually with little higher results. 
But when the milk-casein has been proteolyzed to any extent, 
the use of alum is not permissible, since it precipitates caseoses 
in addition to casein. 
The use of acetic or any other acid in precipitating casein in 
milk, whose casein has been digested in any degree, precipitates, 
in addition to casein, any paranuclein that is present. We have 
not yet succeeded in devising satisfactory methods for the sepa- 
ration of these compounds. 
3. DETERMINATION OF NITROGEN IN THE FORM OF ALBUMIN AND 
SY N'TONIN. 
The filtrate from 2 is neutralized by caustic alkali, using phe 
nolphthalein as indicator and is then heated at the temperature 
of boiling water until the precipitate completely separates and 
settles. The precipitate is then filtered, washed and treated by 
the Kjeldahl method. : 
4. DETERMINATION OF NITROGEN IN THE FORM OF CASEOSES. 
The filtrate from 3 we heat to 158° F. (70° C.), add 1 ec. of 
50 per ct. sulphuric acid and then c. p. zine sulphate to satura- 
tion. Let stand at the temperature indicated until the caseoses 
completely separate and settle. Then cool the mixture, filter, 
wash with a saturated solution of zinc sulphate made slightly 
acid with sulphuric acid, and treat the precipitate by the 
Kjeldahl method. 
5. DETERMINATION OF NITROGEN IN THE FORM OF AMIDO-ACID 
COMPOUNDS. 
Treat about 50 grams of milk with a tannin-salt solution or 
with phosphotungstic acid as described in case of cheese, under 
8, p. 201. 
