11 



volume of oxygen to form two volumes of water-gas 

 or steam. 



E. 257. 1877. Made by J. Schober, Berlin. 



This apparatus consists of a long narrow tube closed at the 

 upper end, and fitted with two platinum wires. The tube is 

 filled with mercury ; and a mixture of two volumes of hydrogen 

 and one of oxygen is admitted into it. This mixture is most 

 readily obtained from the electrolysis of water. The gas-filled 

 part of the tube is entirely surrounded by a glass jacket through 

 which the vapour of atnylic alcohol is driven, the lower end 

 dips in the glass trough containing mercury. The length of 

 the column of mixed gases when fully expanded is marked. A 

 spark is now passed between the platinum wires and the gases 

 combine with an explosion, at the high temperature (132) 

 produced by the arnylic alcohol vapour, the water formed 

 remains as a gas. If the mercury in the tube be now adjusted 

 to its former level with respect to the mercury in the trough, 

 it will be found that the original measure of the gases is 

 diminished by one-third; the remaining two-thirds being steam, 

 which condenses if the tube is allowed to cool. 



74. Apparatus for showing the simultaneous decompo- 

 sition of water, hydrochloric acid, and ammonic chloride. 



Made by J. Schober, Berlin. 

 E. 259, 260, and 261, 1877. 



These three instruments are of similar form, consisting of a 

 U-tube, closed at both ends by stopcocks, and connected below 

 with a tube having a reservoir at the upper end above the level 

 of the U-tube. Two of the instruments are provided with 

 carbon poles, passing through corks in the prolongations of the 

 straight limbs of the tubes, and wrapped round with wire for 

 connecting with the terminals of a battery. The third is pro- 

 vided with poles of platinum foil. The instruments with the 

 carbon poles are used in the decomposition of hydrochloric acid 

 and ammonic chloride. If platinum were used, it would be at 

 once attacked by the chlorine given off and dissolved. 



The two gases collect separately in the two tubes, and may 

 be allowed to flow out through the stopcocks, being driven out 

 by the pressure of the liquid in the large reservoir. The chlorine 

 will not collect until the liquid is saturated with the gas, it 

 being very soluble in water. 



75. Hofmann's lecture-room eudiometer. 



E. 266. 1877. Made by J. Schober, Berlin. 



This apparatus consists of a U-tube, one limb closed at the 

 upper end by a stopcock, and provided with platinum wires 

 fused in the glass ; the other open, and having a tap near the 

 bend. The closed limb in this instrument is graduated, so that 



