of Hydrogen and some other Gases. 313 



with a fine capillary tube C, O'l mm. in diameter through a 

 three-way-cock. One of the three ways in connected with 

 a mercury reservoir D, and to the left end of the capillary 



IS 1 . 5. 



tube, a calcium chloride tube with a long rubber tubing is 

 connected. By this arrangement we can pour into or draw 

 out any desired quantity of water from the glass cup W 

 shown in fig. 3, by forcing the air or sucking it at the end 

 of the rubber tubing F. The reservoir D serves in the case, 

 when a large quantity of water is desired to be supplied or 

 extracted from the cup. 



(b) Compressor and Measuring Tirf>e. 



The compression of the gas was made with a Cailletet 

 hydraulic compressor of an ordinary type. The compressing 

 cylinder was replaced by a cast-iron cylinder, specially 

 designed for the present purpose and having a capacity of 

 1300 c.c. The pressure-gauge was also replaced by another 

 capable of measuring up to 70 atmospheres and graduated 

 to one atmosphere. 



The glass tube, in which the gases are to be filled at a 

 high pressure, has the following construction (fig. 6) : — 



'ihe mechanism of the valve of the measuring tube is 

 similar to that of the pressure-gauge commonly used for 

 compressed-gas-bombs. A is a hollow brass cylinder having 

 two bores in it, a narrow straight hole, 1 mm. wide, is bored 

 through from the left end to the central hole terminating in 

 a cone. In this hole a small brass cylinder P lightly fitted 

 to the hole is pressed on a rubber plate on the right end of the 

 hole by a weak spring. On the left end of this cylinder P r 

 a small piece of ebonite is imbedded. The right opening of 

 the cylinder A is provided with a cup C, which can be 

 screwed into the cylinder, till it firmly presses the rubber 

 plate covering the right opening of the central hole with a 

 thin metal ring. Within the cup 0, there is a piece of 



