Chemical Instruments and Operations. Til 



the mahogany block, communicating with the bore of the 

 tube, a cock, c, furnished with a gallows screw, is inserted. 

 Through the block on each side of the perforation, wires are 

 introduced, so as to be air-tight. To the upper end of these 

 wires, gallows screws, g g^ are attached. The lower ends 

 of the wires, within the tube, are made to communicate by 

 means of a fine platina wire fastened to them by solder. 



The apparatus being so far prepared, let it be firmly fixed 

 over the pneumatic cistern, so that the water may rise about 

 an inch above the lower extremity of the tube. To the gal- 

 lows screws, g, g^ attach two leaden rods, severally proceed- 

 ing from the poles of a calorimotor. By means of a leaden 

 pipe, produce a communication between the bore of the 

 cock, and an air pump, so that by pumping the air from the 

 cavity of the tube, the water of the cistern maybe made to 

 rise into the space thus exhausted of air. On each side of 

 the tube, and between it and each iron rod, there is a strip 

 of wood scored so as to graduate about four inches of the 

 tube into eight equal parts. These parts were measured by 

 introducing into the tube, previously filled with water, one 

 hundred measures of air, from a sliding rod gas measure, 

 eight times, and marking the height of the water after every 

 addition.* As each degree thus indicated by the strips will 

 be equal to one hundred of those of the sliding rod, the whole 

 may be considered either as comprising eight hundred meas- 

 ures of the latter, or as eight volumes, each divisible into one 

 hundred parts, by means of the gas measure. 



The apparatus being so far prepared, and the tube ex- 

 hausted of air so as to become full of water, close the cock 

 leading to the air pump, introduce two volumes of pure hy- 

 drogen, and one volume of pure oxygen, which may be most 

 conveniently and accurately effected by the sliding rod gas 

 measure. The plates of the calorimotor being in the next 

 place excited by the acid, the ignition of the platina wire en- 

 sues, and causes the hydrogen and oxygen to explode. When 

 they are pure, the subsequent condensation is so complete, 

 that the water will produce a concussion as it rises forcibly 

 against the leathern disk, which, aided by the mahogany 

 block, has been represented as closing the upper orifice of 

 the tube. 



See this Journal, vol. xii. page 39. 



