ANALYTIC PROCESSES 13 
weight is sensibly constant. The percentage 
of residue can be easily calculated. About three 
hours may be required to secure constant weight. 
When high accuracy is not essential, it will 
suffice to measure the milk. Vieth advised a 
pipet graduated to deliver 5 grams, and found 
that, working with whole and skimmed milk, 
under the ordinary variations of temperature, 
the error will not exceed 0.1 on the total solids 
and less on the fat. The pipet should have a 
rather wide opening so that no cream will be 
retained. 
The Massachusetts State Board of Health has 
for many years used the routine method of 
evaporating 5 grams for two hours ina flat plati- 
num basin over boiling water. 
The A. O. A. C. method is: Heat at 100° to 
constant weight, about 3 grams in a tared plati- 
num, aluminum or tin dish of 5 cm. diameter, 
with or without the addition of 15 to 30 grams 
of sand. Cool and weigh. 
Ash.—The residue from the determination of 
total solids is heated cautiously over the Bunsen 
burner, until a white ash is left. The result 
obtained in this manner is apt to be slightly low 
from loss of sodium chlorid. This may be 
avoided by heating the residue sufficiently to 
char it, extracting the soluble matter with a few 
c.c. of water, and filtering (using paper extracted 
