The Stratification* of Hydrogen. 411.", 



platinum forming the other pole ; the electrolyte is dilute hydrochloric 

 acid. Platinum wires sealed through the sides of No. 3 carry the 

 current from three Grove's cells to the interior. After the apparatus 

 has had generator No. 1 removed, a large quantity of hydrogen is 

 passed through from the second generator, with the object of replacing 

 the impure hydrogen by some of a purer quality. When No. 2 is 

 exhausted, it also is sealed off at B, leaving only the third generator 

 with its drying tubes connected with the apparatus. Before sealing off 

 No. 2, filling and exhausting is carried on until the hydrogen shows no 

 impurity when spectroscopically examined in a capillary tube attached 

 to the vacuum tube. The gas from the first and second generators 

 bubbles first through strong caustic soda, C, C, C, to remove any acid 



FIG. 5. 



Ice ^die/- 



over from the generators, then through strong sulphuric acid, 

 D, to take away the bulk of the moisture, and thus save the drying 

 tubes ; it then passes through the purifying arrangements more 

 especially connected with the third generator. Having sealed off 

 Nos. 1 and 2, gas is evolved from No. 3 generator. Hence it passes 

 through strong sulphuric acid in the tube H; then over a tube filled 

 with granulated caustic soda, F ; and next through a tube, G, tightly 

 packed with phosphoric anhydride. H and I are two taps, having a 

 reservoir, K, between them. When full of gas, H and I are closed, and 

 the tubes L and M, after having been exhausted to a high point, can 

 then be fed with limited amounts of pure dry hydrogen by slightly 

 opening tap I, and closing it when equilibrium is restored between L, 

 M, and K. N is a spiral of narrow glass tubing immersed in a beaki-: 

 of ice and water. At is a tap to keep mercury from diffusing into 

 the pump if the apparatus has to be left all night. The vacuum tube, 

 L, is provided with aluminium poles, and the tube M has the platinum 

 poles made double for heating purposes, as shown in fig. 3. 



Hydrogen from the first generator was passed through the apparatus 

 for two hours, when it was sealed off. The whole apparatus was 



