336 Mr. Take Sone on the Magnetic Susceptibilities 



halfway with a 50 per cent, solution of caustic potash and 

 placed obliquely, e is a long horizontal tube containing fine 

 pieces of glass wetted with the above solution, /is a bulb 

 for preventing the mixing of the solution of caustic potash 

 with sulphuric acid in a vessel g ; h is a soft glass tube 

 loosely filled with palladium asbestos, and i a thermometer 

 graduated to 360° C. j is a wash-bottle containing strong 

 sulphuric acid, k is a cock dipped in a mercury bath, 

 which prevents the diffusion of hydrogen to the outside and 

 that of air to the inside. I is a tube containing molecular 

 silver, which serves as a sensitive indicator of hydrogen 

 sulphide, m is a large cylindrical tube in which rods of 

 caustic potash are placed, and n a cylinder containing 

 phosphorus pentoxide. o is a large glass bulb having a 

 capacity of about 3 litres, p and q are two glass cocks, the 

 latter being attached to a side tube leading to a Gaede 

 auxiliary pump. All the stopcocks described above are 

 lubricated with Yakuum-Hahnfett and dipped in small 

 mercury baths. The end of the delivery tube r is brought 

 in contact with the tapered end of the compressing cylinder s 

 at v and covered with a thick rubber tube, and this connected 

 portion is dipped in a mercury bath u. The portion extending 

 from the generator to the end of the delivery tube is wholl}' 

 made of glass having no ground joint, except the portion of 

 the stop-cocks, and is therefore entirely safe from the leakage 

 of gases for several months. 



As the rubber connexion between the compressing cylinder 

 and the delivery tube was used only when the compressing 

 cylinder was to be filled with the gas, the diffusion of air 

 through the rubber tube was negligible ; and the gas in the 

 compressing cylinder was proved by an experiment — which 

 will be described later — to be perfectly free from air, so 

 that I could safely use this connexion throughout the whole 

 experiment. 



(b) Filling the Measuring Tube with the Gas. 



The method of filling the compressing cylinder with 

 hydrogen is as follows : — 



To drive off the air contained in the purifying train and 

 the reservoir, a current of hydrogen generated in the 

 decomposing cell, at the rate before described, is passed for 

 about two days, while the palladium asbestos is heated to 

 200° 0. After almost all the air has been driven out of the 



