542 
Journal of Agricultural Research 
Vol. XXI. No. 8 
heat, is applied to the flask, F. Heat should be supplied in abundance 
in the beginning so as to keep the chloroform boiling constantly and 
should be reduced only when the condenser capacity is exceeded. As a 
usual thing there is but little condensation of the chloroform in the 
condenser until the serum temperature exceeds 52 0 . In other words, 
until the temperature of the serum reaches 52 0 the kettle itself acts as 
a condenser. 
The kettle used in the tests has a capacity of 10 liters. It has been 
possible to raise the temperature of this quantity of water in one hour 
from 15 0 C. to 58°, and a temperature of 58° to 6o° has been maintained 
for six hours with a loss of only 20 cc. of chloroform. With a condenser 
functioning properly no loss of chloroform should occur. 
LIQUIDS SUITABLE FOR HEATING MEDIUM 
Of the liquids used, or considered, as heating mediums, chloroform is 
the most satisfactory, since (1) it has a suitable boiling point, (2) it is 
noninflammable, (3) it has a characteristic odor, (4) it is not poisonous, 
(5) it is not corrosive, (6) it is insoluble in water, and (7) it is reasonably 
cheap and easily obtained. Although the boiling point of chloroform 
is 6i° C., it has never been possible to raise the temperature of the serum 
in the kettle above 6o° even when sufficient heat was applied to overtax 
the condenser. 
In altitudes greater than that of Washington, D. C., it may be neces¬ 
sary to use a liquid of higher sea-level boiling point than chloroform. It 
is believed that the most suitable liquid for this purpose is a mixture 
of carbon tetrachlorid and chloroform. Carbon tetraehlorid boils at 
74 0 C. at sea level, and so mixtures of it and chloroform may be prepared 
with boiling points at sea level varying from a little above 61 0 to a little 
below 74 0 , depending upon the quantity of each liquid present. For 
example, at an altitude of 5,000 feet the boiling point of chloroform is 
considerably lower than 6i°. In this case a mixture of carbon tetra¬ 
chlorid and chloroform having a boiling point of 6i° should be prepared. 
The proportion of carbon tetrachlorid to chloroform that will give a 
mixture having a boiling point of 61 0 for a given altitude can be easily 
determined by preparing several mixtures of the two liquids in varying 
proportions and determining the boiling point of each. In this way the 
proportion of carbon tetrachlorid to chloroform that is required to give 
a mixture with boiling point of 61 0 at the altitude in question may be 
ascertained. 
If a liquid of lower boiling point than 61 0 C. at sea level should be 
desired, acetone, which has a boiling point of 58°, is suggested. Acetone, 
however, is inflammable and is soluble in water. 
In all cases where mixtures are used, the utmost precaution should be 
taken to insure the perfect condensation of the vapors, since otherwise by 
