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investigation are required. For further details concerning methods 
of milk analysis, the reader is referred to the following standard 
works on this subject, viz, Modern Methods of Testing Milk and 
Milk Products, Van Slyke, New York, 1907; and Food Inspection 
and Analysis, Leach, New York, 1907. The chemical examination 
of the Washington milk supply has included the determination of 
specific gravity, total solids, fat, sugar, ash, acidity, refractometer 
reading, quantity of dirt by volume, and tests for preservatives. 
During the month of September special attention was paid to the 
examination for preservatives, and during this time the determination 
of sugar and total solids was omitted. The latter were calculated 
from the specific gravity and the percentage of fat according to Bab- 
cock’s rule. The samples submitted for examination were collected 
by certain inspectors of the health office, and as soon as collected were 
put on ice and kept there until delivered at the Hygienic Laboratory, 
and until the chemical examinations were completed. As soon as 
the sample was brought into the laboratory, the acidity of the milk 
was determined on 50 cubic centimeters of the sample. The specific 
gravity and the percentage of fat and also the refractometer reading 
(the latter on the milk serum) were also determined practically as 
soon as the sample reached the laboratory, especially in those cases in 
which owing to lack of time the total solids were not determined by 
weighing, and in the event that these determinations indicated that 
any particular sample was below standard, the total solids on this 
particular sample were determined by weighing in the manner de- 
scribed in the following: 
Specific gravity . — The specific gravity of the milk was determined 
either by means of the Westphal balance or by means of the Que- 
venne lactometer. 
Total solids and ash . — The total solids and ash were determined by 
the method recommended by Leach (1). This method consists in 
heating 5 grams of the milk on the steam bath for three hours, in 
small flat platinum dishes. At the end of this time the dishes were 
removed from the steam bath and while still hot were wiped dry 
with a piece of soft toweling. They were then allowed to cool and 
weighed. In this way we obtained the weight of the residue from 
5 grams of milk, and from this we calculated the percentage of total 
solids. The ash of the milk was then determined on the same sample 
by ignition at a low red heat, cooling and weighing the dish and its 
contents the second time. The ash left after this operation was tested 
for boric acid by the turmeric test. 
