T7ic Stratifications of Hydrogen. 399 



IV. " On the Increase of Electrical Resistivity caused by Alloying Iron 

 with Various Elements, and the Specific Heat of those 

 Elements." By Professor W. F. BARRETT, F.R.S. 



V. " Continuous Electrical Calorimetry." By Professor H. L. 

 CALLENDAR, F.R.S. 



" The Stratifications of Hydrogen." By Sir WILLIAM CROOKES, 

 F.R.S. Received January 9. Read February G, 1902. 



The following pages give the outcome of attempts to prepare pure 

 hydrogen, and experiments ou the stratifications exhibited by the 

 purified gas under the influence of an induction current. The 

 researches were commenced in 1884 and have been continued inter- 

 mittently to the present time. 



The original apparatus consisted of a vacuum tube of soda-glass, 

 6 inches long and -^ inch wide, having sealed-ill aluminium terminals 

 at each end. The pole at one end was ring shaped, at the other 

 pointed. The vacuum tube was connected to the mercury pump at 

 one end, a tightly packed phosphoric anhydride tube intervening. 

 At the other end was another phosphoric anhydride tube, a hydrogen 

 generator of zinc and dilute sulphuric acid and a tap to control the 

 flow of gas. The hydrogen was passed through the apparatus for 

 some hours, and the whole was exhausted to a high point, re-filled, 

 and again exhausted. This was repeated many times; but, on ex- 

 hausting to the stratification-point, I could get no spectrum which did 

 not show, in addition to hydrogen, also mercury. 



The apparatus was therefore modified. Strips of palladium foil 

 were charged with hydrogen by the electrolysis of dilute sulphuric 

 acid; a 4-cell Grove's battery being used for 1 hour. After drying, 

 the palladium strips were put in a glass tube and sealed between the 

 generator and vacuum tube. At first, crude gas from the generator 

 was used to wash out the apparatus, and after many fillings and 

 exhaustions the last to the highest possible point the generator 

 and tap were sealed off, leaving only the palladium and drying tubes 

 .attached to the apparatus. A portion of the palladium was now 

 gently heated; the gauge sank 12 cm., when it was again well 

 exhausted and a little more hydrogen liberated. This was repeated 

 three times, when the tube was exhausted to the stratification-point 

 about 4 mm. 



Parti-coloured Stratifications. 



The strata were twelve in number, and of a slightly concavo-convex 

 button-shape, each of a blue colour on the convex side facing the 

 negative pole, and pink on the other side. On reversing the current, 



2 F 2 



