94 



SEC. 13. CHEMISTRY. 



walls of the bag is found to contain 42 per cent, of oxygen, that is, 

 the per-centage of oxygen present is doubled. 



(2.) The penetration of metals by gases was studied by the aid of metallic 

 tubes, of which the palladium tube shown is one. It was enclosed 

 in a tube of glass or porcelain, and rendered vacuous by the aid of a 

 Sprengel exhauster ; a stream of gas was then passed through the 

 annular space between the tubes. In the cold no hydrogen will pass 

 through palladium, but at a red heat the gas passes at a rate of 

 nearly 4000 cubic cent, per square metre of surface in a minute. 



2547. Apparatus for Gas Experiment, as used for the 

 determination of the Composition of Ozone. 



Sir B. C. Brodie. 



This apparatus will be described in the form in which it was employed for 

 the determination of the composition of ozone, the object being to determine 

 the changes which electrized oxygen underwent when subjected to the action 

 of heat or of chemical reagents. 



A current of pure and dry oxygen was passed through an induction tube, 

 fundamentally of the kind devised by Siemens, but the inner tube was nearly 

 filled with water, in which was placed one of the terminal wires of Ruhm- 

 korffs coil, the tube itself being immersed in a vessel of water connected 

 with the other terminal wire of the coil. The tube is delineated in Fig. 1. 

 The gas enters the apparatus at A, and, passing over anhydrous-phosphoric 

 acid contained in the three bulbs i, traverses the narrow space k between the 

 two tubes, and is there submitted to the electric action, after which the 

 electrized gas is again passed over anhydrous phosphoric acid contained in 

 the three bulbs /, and is delivered at m. 



F/Q.;. 



The electrized gas is collected and preserved for the purpose of experiment 

 in a gas-holder, delineated in Fig. 2. On this side of the induction tube 

 connexions of caoutchouc can no longer be employed, this substance being 

 instantaneously corroded by even the minutest trace of ozone, and the friction 

 between the gas-holder and the induction- tube is effected by means of what 

 may be termed a paraffin joint. Over the tubes to be connected, which are 

 placed close together, is slipped a piece of glass tube into which they exactly 

 fit, and from which they are separated by a capillary space ; a fragment of 

 pure paraffine is placed at the external junction of the tubes. The union of 

 the tubes is effected by gently melting the paraffin ; the liquid paraffin is 

 extremely limpid, and runs into and fills up the narrow space between the 



