NEW FORM OF BOMB CALORIMETER. jbl 
by the heat developed when the substances are burned with 
oxygen he may employ a method for determining the amount of 
heat thus developed. 
But it is not the physiological chemist alone to whom the 
method and apparatus for measuring heats of combustion is 
essential. Inquiry in this special field is of fundamental import- 
ance in physical chemistry generally, and research has demon- 
strated its necessity for that understanding of the molecular 
structure of compounds which has become one of the most 
important factors of the development of those branches of 
chemical science to which the terms ‘“‘ organic”’ and “theoretical ”’ 
are commonly applied. And finally, the chemical technologist, 
who is endeavoring to learn the values of coal and other fuel 
materials for heating, experiences the necessity of a means for 
determining their heats of combustion. Various forms of calori- 
metric apparatus have been devised for this purpose.* The Stoh- 
mann calorimeter,+ which is a modification of that of Thompson, 
was employed for the studies of heats of combustion by Dr. H. B. 
Gibson, which were described in the report of this Station for 1890. 
In the combustions by the Thompson-Stohmann method the 
oxygen is obtained from potassium chlorate. Considerable time 
is required for the determination, but the chief difficulty with this 
method is that the combustion is not always complete. 
THE BERTHELOT BOMB CALORIMETER. 
Berthelot has devised an apparatus{ and, with the assistance of 
Vieille and others, has developed a method for the use of oxygen 
under high pressure. The apparatus consists essentially of a steel 
bomb lined with platinum, within which the substance is burned. 
The bomb is immersed in water contained in a metal cylinder; this 
calorimeter cylinder is placed with its contents inside of con- 
centric cylinders containing air and water. The heat developed 

* See discussion of the general subject of metabolism of energy in the body and descriptions 
of calorimeters in Bulletin 21 of the Office of Experiment Stations of the U.S. Department 
of Agriculture, from which portions of the statements herewith regarding bomb calorimeters 
are taken. The engravings of the calorimeter beyond are from the same publication and are 
used here by courtesy of the Department. 
+ This apparatus is described in the Bulletin just referred to. See also the original descrip- 
tion by Stohmann, with diagram; Landw. Jahrbiicher, 13, 1884, 513. The apparatus is 
pictured in the Century Magazine for July, 1887. 
+ For descriptions see Berthelot, Ann. Chim. Phys. (5), 23, 160; Berthelot & Vieille, ibid., 
(6) 6, 546 Berthelot, Traité pratique de calorimétrie chimique, Paris, 1893, p. 128, and, for an 
especially clear account of the apparatus and method, Stohmann, Jour. f. prak. Chem., 147 
(N. F. 39), 1889, 503. An engraving of the bomb with a brief description may be found in 
Fres. Zeitsch. Anal. Chem., 1893, 77. A Berthelot apparatus employed by Stohmann was 
obtained from Golaz in Paris, who made it in accordance with Berthelot’s directions. It cost, 
with accessories, including compression pump, etc., not far from $1,200. Aside from those used 
in Berthelot’s laboratory and the one made for Stohmann, extremely few have been made. 
