29 



stopcock, and then connecting it with a receiver standing over 

 water and containing a mixture of hydrogen and oxygen in the 

 proportions requisite to form water. The stopcock being first 

 opened and then closed, the mixture is exploded by the electric 

 spark. After the explosion, the interior will be perceptibly 

 moistened by minute drops of water. 



122. Apparatus to prepare acetylene from hydrogen 

 and carbon. 



E. 67. 1874. 



This is a globe, designed to contain hydrogen, with two 

 carbon electrodes nearly meeting in the centre. A Grove's 

 battery of 20 cells is to be connected with these electrodes, 

 which must first be pushed together and afterwards separated so 

 as to produce the voltaic arc. Under the influence of the heat 

 thus generated, combination ensues between the carbon and 

 hydrogen, and acetylene in small quantity is formed. 



123. Twenty cells of Grove's battery. 

 E. 68. 1874. 



To be used with the preceding. 



124. Apparatus for preparing acetylene from coal-gas 

 by a stream of electric sparks. 



E. 69. 1874. 



This much resembles No. 16, a current of coal-gas being sub- 

 stituted for one of hydrogen, and the sparks obtained from the 

 coil No. 1. 



125. Model apparatus for coal-gas. 

 E. 70. 1874. 



Intended to illustrate the manufacture of coal-gas. The copper 

 retort is to be charged with coal and heated to redness in a 

 charcoal furnace. The Woulffs bottle is intended to arrest tarry 

 matter ; the gas is then conducted through slaked lime or ferric 

 hydrate to remove sulphuretted hydrogen, and is afterwards 

 collected in jars or in a gasholder, from which it may be burnt 

 at a jet. Care must be taken that all the air is expelled from 

 the apparatus before the gas is collected. 



126. Apparatus for exposing equal volumes of hydro- 

 gen and marsh-gas to various temperatures and pressures. 



E. 71. 1874. 



Equal volumes of two gases are placed in the two limbs of the 

 U-shaped tube. The pressure may be increased by addition of 

 mercury in the open tube, or diminished by running off mercury 

 from the pinchcock at the bend. A glass cylinder surrounding 

 the U'tube containing the gases forms a steam jacket, and affords 

 the means of rapidly raising the temperature of the enclosed 

 gases to 100 C. 



U G4846. 



