404 Sir W. Crookes. 



I) open. Electrolysis was then commenced (D being closed), and the 

 tap E was slightly turned until the escape of hydrogen into the 

 apparatus was equal to the speed of its generation. The apparattis 

 was filled, and several times exhausted, until no improvement in the 

 spectrum or stratifications could be seen. The electrolytic cell was 

 then sealed off at a narrow constriction between the first potash tube, 

 F, and the phosphoric anhydride tube, G. After good exhaustion one 

 of the branch tiibes of palladium was heated, when the gauge sank 

 several centimetres. Exhaustion and re-filling from fresh palladium 

 were repeated until no alteration was detected in the appearance of the 

 strata. Then, for the first time, I obtained hydrogen strata showing 

 no blue, either throughout the tube or concentrated in front, whilst the 

 most careful examination showed no mercury. The stratifications 

 were all pink, and showed the hydrogen lines strongly. 



Many disadvantages were noticed in the apparatus just described, 

 the chief being the danger of introducing more impurities than Avere 

 kept out by the copper, sulphur, and iodine tubes. The palladium 

 method of introducing hydrogen was not altogether satisfactory, as 

 only small quantities could be dealt with, and occasionally at a critical 

 point the store Avas exhausted. Also, the electrolytic generator of 

 hydrogen Avas too small. It was decided, therefore, to devise and tit 

 up an entirely new piece of apparatus. In this another method Avas 

 used for keeping out the mercury. It had been noticed that the 

 diffusion of mercury from the pump proceeded the more sloAvly as the 

 distance from the pump and the narrowness of the connecting tubes 

 increased. It Avas thought that by introducing a long narrow spiral 

 betAveen the pump and the apparatus, one complicated system of tubes, 

 with their attendant dangers, could be removed ; the result shoAved 

 this supposition to be correct. Two vacuum tubes were employed, 

 one having aluminium the other platinum terminals. The hydrogen 

 generators were increased in size and number, and were so distributed 

 that they could be sealed off one after the other during the progress 

 of the experiment. 



Stratifications in Pure Hydrogen. 



The arrangement of the apparatus is shown in fig. 5. The three 

 hydrogen generators are called Nos. 1, 2, and 3. In No. 1, the gas is 

 generated by the action of hydrochloric acid on zinc. This cmde 

 hydrogen is only used to drive out the air from the rest of the 

 apparatus and to remove the air dissolved in the liquids. When it 

 had done its Avork, the generator was sealed off between Nos. 1 and 2, 

 at A. It was considered that having the apparatus to begin with full 

 of even someAvhat impure hydrogen Avas better than starting with it 

 full of air. The second and third generators contain at the bottom a 

 pasty amalgam of mercury and zinc forming one pole, and a piece of 



