LOW TEMPERATURES AND REFRIGERATION—MARCHIS. 215 
“In view of the high degree of interest which attaches to the car- 
rying out and coordinating of scientific research in the field of low 
temperatures, the congress resolves, that the bureau of section A 
shall be charged with the organization of a permanent international 
association for the study of all scientific questions relating to low 
temperatures.” 
II. REFRIGERATING MEDIA. 
In the storehouses where at the present day foodstuffs are pre- 
served by refrigeration, low temperatures are obtained by the vapor- 
ization of the following liquefied gases: Ammonia, sulphurous an- 
hydride, carbon dioxide, and methyl chloride. 
The liquefaction of these refrigerating agents may be attained (1) 
by means of a compression pump (compression machines) ; (2) by 
means of a solvent such as water (absorption machines). In the 
compression machines, which are at present the most widely used in 
the refrigerating industry, the gas liquefied in the condenser or lique- 
fier, passes by way of a regulating cock into the refrigerating cham- 
ber or evaporator; there it is vaporized by a pump which draws out 
the vapor, compresses it, and sends it to be liquefied again in the con- 
denser. In the absorption machines there is also a liquefier connected 
with a refrigerating chamber by a stopcock. The compressor—the 
aspirating and force pump—is replaced (a) partly by an absorber 
in which the vapors from the refrigerator (in these machines as a 
matter of fact ammonia gas is used) are dissolved in water; (0) 
partly by a boiler where the heated ammonia solution gives off am- 
monia gas. This is again condensed in the liquefier. 
The utilizable effect of such a machine, or its refrigerating power, 
is measured by the quantity of heat absorbed in the refrigerator dur- 
ing a certain period, or as is sometimes said, the quantity of cold de- 
veloped in the refrigerator during the same period. 
As M. Barrier has remarked, this power varies widely with the 
temperature of the refrigerating agent at the condenser and at the 
refrigerator. The specification of these temperatures affords the 
only means of comparing with any exactitude the claims of machines 
made by different constructors, and the only means of avoiding dif_- 
culties in commercial contracts and exchanges. 
Furthermore, different countries adopt different units to express 
this refrigerating power. In France and Germany they express the 
refrigerating capacity by the number of kilogram-calories absorbed, 
or kilogram-frigories (negative calories freed per hour). In Eng- 
land and in the United States they prefer to measure the refrigerat- 
ing capacity for a day of 24 hours and express it in tons of refrig- 
eration, but in England the refrigeration ton is equal to 81,300 
kilogram-frigories while the refrigeration ton in the United States 
45745°—sm 1909——15 
