13 



79. Hof rnann's tube, U~f rm with five stopcocks and 

 four steam jackets, for snowing the influence of tempera- 

 ture and pressure on compound gases. Price II. 15s. 



1876. Exhibited by J. Orme $ Go. 



80. Hofmann's electrolytic apparatus for the decompo- 

 sition of hydrochloric acid. 



E. 255. 1877. Made by Julius Schober, Berlin. 



This apparatus consists of a V-shaped glass tube, with one 

 closed and one open limb, the former being provided with a 

 platinum wire, fused into the glass and terminating near the 

 bend in a piece of platinum foil. Hydrochloric acid, coloured 

 with indigo, is introduced so as to fill the closed limb and half 

 the open one. If we connect the negative pole of the battery with 

 the closed limb, at the same time connecting the positive pole 

 with the platinum foil in the other, we observe that gas is almost 

 exclusively evolved at the negative pole in the closed limb, the 

 gas at the other only being noticeable by its suffocating odour 

 and its bleaching action on the indigo coloured solution. The 

 gas in the sealed limb is transferred to the open limb, previously 

 filled with water and closed by the thumb, and tested. It will 

 be found to be inflammable and may be recognised as hydrogen. 



If the poles are now reversed hydrogen escapes at the open 

 limb, and after some time we are able to collect a greenish-yellow 

 gas in the sealed limb, which may be proved to be chlorine. 



This apparatus may also be used in a similar manner for the 

 decomposition of water into hydrogen and oxygen. 



81. Hofmann's tube, with bulb and two stopcocks for 

 showing that chlorine and hydrogen combine to form 

 HC1 without alteration of volume. Price 5s. 6d. 



1876. Exhibited by J. Orme fy Co. 



82. Hofmann's apparatus for demonstrating that the 

 volumes of oxygen which enter into the composition of 

 carbon and sulphur dioxide are equal to the respective 

 gas volumes of these compound gases. 



B. 267. 1877. Made by Julius Schober, Berlin. 



This apparatus consists of a U-tube with a bulb blown on the 

 end of one limb, capable of being closed with a stopper, through 

 which are passed copper wires, one sustaining a deflagrating 

 spoon to contain carbon or sulphur, the other nearly touching it, 

 the ignition being effected by a fine platinum wire connecting 

 the two through which the electric current passes. The bulb 

 being filled with dry oxygen, and the level of the mercury in 

 the limbs being marked, the current is passed and the carbon 

 or sulphur ignited ; on cooling it will be observed that no 



U 64846. B 



