53 CALORIFIC POWER OF FUELS. 



little phosphorus or sulphur. Tensile strength tests are the 

 best criterion of quality. 



It has a capacity of 654 cc. (40 cubic inches) at 15 C. It 

 is gauged with a balance showing -jnrJinF' The total weight 

 is about 4 kilograms (8.8 Ibs.) with the accessories.* The 

 metal of the walls is 8 millimetres (about 0.3 inch). 



The capacity is greater than Berthelot's, and has the ad- 

 vantage of insuring perfect combustion of carbon in all cases y 

 due to a certain excess of oxygen, even when the purity of 

 this gas as bought is not quite satisfactory. Besides, it is 

 designed to study all industrial gases, even those containing 

 a large percentage of inert gas ; hence it must be able to use 

 a sufficiently large quantity to generate the required tempera- 

 ture. The contraction at the top aids in enameling. 



The shell is nickeled on the outside, while internally it 

 has a coating of white enamel, resisting corrosion and oxidiz- 

 ing action of the combustion. f It does not, however, offer 

 resistance to the heat, being very thin, and it weighs only 

 about 20 grams (308 grains). 



It is closed by an iron stopper made tight by a lead washer 

 (P, Fig. 33) and clamped down. This carries a conical-seated 

 stop-cock, R, of fine nickel a metal almost unoxidizable. 

 An electrode well insulated and reaching the interior by a plat- 

 inum wire runs through the stopper. 



Fig. 24 shows most of the details. 



Another platinum wire, also fixed on the cover, supports 

 the platinum disk or foil on which the fuel is placed. 



The calorimeter, the non-conducting material, the support 

 for the shell in the water, and the agitator differ in numerous 

 details from those of Berthelot, and are much cheaper. 



* Slight modifications have been made in the dimensions of the metal of 

 the bombs made lately by Golaz. 



f Prof. W. O. Atwater finds that the enamel chips off in time, and that 

 after about 300 combustions it requires re-enameling. Hempel for coal 

 determinations uses one without any inside enamel. 





