138 STORRS AGRICULTURAL EXPERIMENT STATION. 
is measured by the rise in temperature of the water, due allow- 
ance being made for the heat absorbed by the metal of the 
apparatus and for that introduced in igniting the substance by 
an electric current and developed by the oxidation of an iron 
wire through which the current is passed, and in the formation of 
a small amount of nitric acid. The reactions are simple, the 
oxidation of the compounds in completing the determination 
requires a comparatively short time, and the results are very 
satisfactory. The only drawback is the great cost of the 
apparatus, which is due to the large amount of platinum employed 
in its construction. It is doubtless because of this that the bomb, 
which is most useful for its purpose and would be highly prized 
in many laboratories, has not come into common use. 
The bomb calorimeter was first used. by Berthelot in measuring 
the heats of combustion of gases by detonation. The gas to be 
burned was mixed with the exact amount of oxygen required, or 
a slight excess, at ordinary atmospheric pressure within the bomb 
and ignited by the passage of an electric spark. Gases were 
easily burned in this way, but the combustion of solids was im- 
practicable. Attempts were made to remedy the difficulty with 
solids by intimately mixing them with potassium chlorate and 
as good results were obtained: as in the Thompson-Stohmann 
method. Berthelot and Vieille* found later,+ however, that when 
oxygen was introduced under a pressure of from 7 to 25 atmos- 
pheres, the combustion was complete with all organic substances 
even when no potassium chlorate was added. 
The bomb originally employed by Berthelot was in the shape 
of a cylinder, with hemispherical ends and divided in two parts, 
one of which screwed into the other. It was made of steel with 
the interior lined with gold by electro-plating. 
The later and permanent form of Berthelot’s bomb is cylindri- - 
cal with a rounded bottom and flat cover. It is made of steel 
with a heavy lining of platinum. The size may vary. Inthe 
one made by Golaz for Stohmann the diameter is approximately 
Io centimeters and the height to the upper surface of the cover 
about 13 centimeters; the walls are somewhat over a centimeter 
in thickness. It contains 2,717 grams of steel and 1,233.3 grams 

* Ann. Chim. Phys., (6) 6, 546. 
+ In 1885. The principle was discovered and investigated by Frankland in 1864 and 1868. 
See investigations by him ‘t On the combustion of iron in compressed oxygen.’’ Jour, Chem. 
Soc. II., 1864; 52. ‘‘On the combustion of gases under™pressure.’’ Brit. Assoc. Rep. 
XXXVIII., 1868 (Sect.); 37. ‘On the combustion of hydrogen and carbonic oxide in oxygen 
under great pressure.’’ Proc. Roy. Soc. XVI., 1868; 419. 

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