SIR ANDREW NOBLE: RESEARCHES ON EXPLOSIVES. 203 



to the gasometer C or at pleasure into the gas tubes D, which, before the experi- 

 ment, are filled with mercury, the stop-cocks above and below being closed ; E is 

 a thermometer for determining the temperature of the gas when its volume is 

 measured. 



Immediately after the explosion, if the vessel be quite tight, the valve at B is 

 very slightly opened and the gas allowed to pass slowly through the tube F, containing 

 pumice-stone and concentrated sulphuric acid, into the gasometer. 



When it is quite certain that all air is removed from the conducting tubes, the 

 gas is allowed to flow into one of the gas tubes D, and shortly afterwards or at fixed 

 intervals of time into the other two tubes, the quantity of gas in the tubes being 

 added to that measured in the gasometer, the height of the barometer and the 

 temperature of the gas at the moment of measurement being also determined. 



When the whole of the gas has been transferred to the gasometer, and the 

 temperature and barometric pressure taken, the cylinder is opened. A considerable 

 quantity of water is always found ; as much as possible of this water is collected by 

 means of a weighed sponge placed in a weighed vessel, and closed by a ground glass 

 plate. The amount of the water so collected is determined by weighing in the usual 

 manner. 



After all the water that it is possible to remove with the sponge is collected, a 

 weighed vessel of calcium chloride is placed in the cylinder, which is then closed, and 

 left for one or two days, when the same procedure is followed with a second calcium 

 chloride vessel, after which the cylinder is generally found to be perfectly dry. 



The next point to be determined is the amount of heat generated by the explosion. 



For this purpose a strong steel vessel, the section of which is shown in Plate 2, 

 and of which the heat capacity is carefully determined, is employed. The calori- 

 meter used is practically of the same construction as that described by OSTWALD in 

 his ' Manual of Physico-Chemical Measurements.' 



A section of this calorimeter is also shown in Plate 2, the corresponding inner and 

 outer surfaces of the several vessels being nickel plated. For some hours before the 

 experiment the calorimeter is kept in a room maintained at as even a temperature as 

 possible, the explosion vessel itself with the charge to be exploded being kept in the 

 water as shown, so that the whole system may assume practically the same 

 temperature. 



The rise of temperature due to the explosion being approximately known from 

 previous experiments, the water in the outer cylinder before firing is kept at a 

 temperature about half way between the initial and final temperatures of the inner 

 vessel. 



The thermometers employed for these determinations are calorimetric, specially 

 made for calorimetric experiments, and are only used for observing changes of 

 temperature, and not for determining absolute values. The range of measurement 

 in the thermometers I used was about 8 C., but by a special contrivance these 8 



2 D 2 



