NEW FORM OF BOMB CALORIMETER. I4I 
pressure. ‘The outcome of the experience was the use of a lining 
of platinum one-half millimeter in thickness. 
THE BOMB CALORIMETERS OF MAHLER AND OF HEMPEL, 
Various modifications of Berthelot’s apparatus have been 
devised especially to obviate the difficulty of expensive lining. 
Mahler uses a bomb of forged steel with enamel lining.* The 
cylinder is somewhat narrowed at the top and the cover is 
screwed directly upon it, the junction being made tight by a 
washer of lead. The enamel is easily put on or replaced, and it. 
is stated that a single coating has been used for 300 combustions 
without injury. I have understood, however, that the enamel is 
apt to scale off in constant use. The form described by Mahler 
has an internal capacity of 600 cubic centimeters or nearly double 
that of Berthelot’s bomb, as above described. 
Prof. Hempel of Dresden uses, for determination of heats of 
combustion of coal, a simple bomb of steel without lining. The 
principle, like that of Mahler’s form, is the same as that of 
Berthelot. The closure is by a “head piece” which screws 
into the neck of the bomb. It suffices very well for technical 
purposes but is not recommended for scientific use. + 
THE BOMB CALORIMETER HERE USED. 
In accordance with suggestions by one of us during a sojourn 
in Dresden, Prof. Hempel most kindly had a bomb made by 
the mechanicians who make the bombs of his devising just re- 
ferred to and lined, by Heraeus of Hanau, with a thin sheet of 
platinum. Through Prof. Hempel’s pains-taking care added to 
his inventive skill and his peculiarly thorough familiarity with 
the whole subject, an apparatus was obtained which has proved 
most efficient. The principle is the same as Berthelot’s form; 
but whereas Berthelot’s cover fits into the cylinder in the manner 
of a very wide stopper, the cover in this, as in Mahler’s, rests 
directly upon_the upper edge of the cylinder, a projection of the 
latter fitting into a groove in the former. A washer of lead is 
set in the groove of the cover, the latter is held tightly to the 
cylinder by a screw cap or collar and thus perfect closure is 
easily secured. The apparatus differs but slightly from that 
depicted in figure 1 herewith. 

* Compt. rend., 113, 774 and 862, and Génie Civile, Jan. 23, 1892, p. 198. See also Zeitsch. 
f, anal. Chem., 1893, 79, and Berthelot, Calorimétrie Chimique, 133. 
‘+ Hempel, sche Methoden, 1890, 355 and English translation, Methods “ Gas 
Analysis, 1892, p. 359. 
