174 PEOFESSOR H. B. DIXON AND MR. E. C. EDGAR 



drying tubes were employed, each 1 metre in length and 2 '5 centims. in diameter, 

 filled with small pieces of purified potassium hydrate. The gas then passed through 

 a U-tube containing platinised pumice, kept at a temperature of 220 C., in order to 

 remove any oxygen diffusing from the + electrode, and then through a short 

 horizontal tube and three long U -tubes filled with pure phosphorus pentoxide. As 

 recommended by COOKE, the phosphorus pentoxide was packed closely into the 

 drying tubes and was alternated at frequent intervals with plugs of clean glass-wool. 

 To ensure efficient drying, the current of hydrogen was passed through these drying 

 tubes at a rate not greater than 2 litres an hour. At the end of our experiments the 

 last layers of phosphorus pentoxide had picked up so little moisture that a slight 

 tapping of the tube threw the powder into a cloud. 



The drying tubes, when filled, were fused together, and to the last phosphorus 

 pentoxide tube was fused the tap C. This, in turn, was fused to one limb of a 

 T-piece, to the other two limbs of which were fused the bulb containing the palladium 

 foil and the Toepler pump. To the first potassium hydrate drying tube at the other 

 end of the apparatus was fused a three-way tap. The U-tube E. in which the 

 electrolysis of barium hydrate was carried out, was also fused to D, whilst the third 

 arm of D opened into the air. 



When the current was passed through the warm barium-hydrate solution between 

 the platinum electrodes G and G,, the evolved gases were allowed to escape into the 

 atmosphere until the air, which was originally contained in the two arms of the 

 U-tube, had been replaced by hydrogen and oxygen respectively. Connection with 

 the atmosphere was then cut oft' by closing the tap H and by fusing off the capillary 

 portion of the opening F. During our experiments the solution showed no signs of 

 milkiness and no precipitate settled at the bottom of the tube ; we believe, therefore, 

 that no carbonate was present. 



The preparation and occlusion of hydrogen was carried out as follows : Before the 

 fusion of the palladium bulb to the apparatus, the tubes on the right-hand side of the 

 tap D were exhausted as far as possible by means of the pump. The U-tube, 

 containing the solution of barium hydrate, was raised to a temperature of 60 C. in a 

 water-bath (in order to dissolve the hydrate which had crystallised out from the 

 solution) and the electrolysis commenced. The evolved oxygen escaped into the air 

 through the tap H and the tube K, filled with a dried mixture of CaO and Na 2 SO 4 , 

 while the hydrogen was admitted, by very cautiously opening the tap D, to the 

 evacuated part of the apparatus. The stream of hydrogen was continued until the 

 bubbling of the gas through the manometer tube showed that the previously evacuated 

 portion of the apparatus was now full. The electrolysis was discontinued, the tap D 

 closed and the drying tubes again evacuated. This operation of filling and exhausting 

 was repeated twelve times in order to get rid of all traces of air. The taps C and D 

 were then closed and the electrolysis stopped. 



The bulb A containing the thin palladium foil was then fused to the apparatus. 



