376 



NA TURE 



[February 20, 1902 



hydrogen coiupounils. h ii llien allowed to cool, and is pounded 

 and sifted so as to get it in the form of granules, averaging a 

 mm. in diameter. Ignited asbestos is packed at each end of 

 the tubes to keep the contents from blowing out when the 

 vacuum is proceeding, or air is suddenly let in. Next follows a 

 tube, N, N, constricted in the middle, containing in the first 

 half phosphoric anhydride, and in the second finely powdered 

 dry caustic potash. A tap, o, connects the apparatus with the 

 pump to prevent diffusion of mercury when the pump is not in 

 use. All parts of the apparatus were built up in place and 

 sealed together with the blowpipe. The glass was new, and 

 the apparatus had been kept apart from mercury until it was 

 sealed together. 



The apparatus was exhausted from air, the tap E being closed 

 and D 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 apparatus was filled, and several times ex- 

 hausted, 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, <;. .\fter good exhaustion, one of 

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

 several centimetres. Exhau-stion and refilling from fresh pal- 

 adium were repeated until no alteration was detected in the 

 -ppearance 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 

 ihowed no mercury. The stratifications were all pink, and 

 showed the hydrogen lines strongly. 



Many disadvantages were noticed in the apparatus iust 

 described, the chief being the danger of intro- 

 ducing more impurities than were kept out by 

 the copper, sulphur and iodine lubes. The pal- 

 ladium method of introducing hjdrogen was 

 not altogether satisfactory, as only small quan- 

 tities could be dealt with, and occasionally at 

 a critical point the store was exhausted. Also, 

 the electrolytic generator of hydrogen was too 

 small. It was decided, therefore, to devise and 

 fit up an entirely new piece of apparatus. In 

 this another method was used for keeping out 

 the mercury. It had been noticed that the 

 diffusion of mercury from the pump proceeded 

 ihe more slosvly as the distance from the pump 

 and the narrowness of the connecting tubes in- 

 creased. It was thought that by introducing a 

 long narrow spiral between the pump and the 

 apparatus, one complicated system of tubes, with 

 their attendant dangers, could be removed ; the 

 result showed this supposition to be correct. Two vacuum 

 tubes were employed, one having aluminium, the other pla- 

 tinum 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. 



Slratifiialiom in Pure Ilydiogeii. 



The arrangement of the apparatus is shown in I"ig. 5. The 

 three hydrogen generators are called Nos. i, 2 and 3. In No. 

 I the gas is generated by the action of hydrochloric acid on 

 zinc. This etude hydrogen is only used 10 drive out the air 

 from the rest of the apparatus and to remove the air dissolved 

 in the liquids. When it had done its work, the generator was 

 sealed off between Nos. i and 2, at .\. It was considered that 

 having the apparatus to begin with full of even .somewhat im- 

 pure hydrogen was better than starling 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 

 platinum forming the other pole ; the electrolyte is dilute hydro- 

 chloric 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. i 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 11, 

 leaving only the third generator with its drying tubes connected 

 with the apparatus. Before sealing off No. 2, filling and ex- 

 hausting 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, 1 , r, to remove any 

 acid carried over Irom 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. I and 2, gas is evolved from No. 3 

 generator. Hence it passes through strong sulphuric acid in 

 the tube II ; then over a lube filled with granulated cau.stic soda 

 V ; and next through a tube, o, tightly packed with phosphoric 

 anhydride. 11 and i are two laps, 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 I., M and K. N is a spiral of narrow glass tubing 

 immersed in a beaker of ice and water. At o is a tap to keep 

 mercury from diffusing into the pump if the apparatus has to be 

 left all night. The vacuum tube, i , is provided with aluminium 

 poles and ihe 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 sea led off. The whole 

 apparatus was exhausted to a high point and No. 2 generator 

 was set to work. Hydrogen was passed several times at full 

 pressure through the apparatus for one or two hours and then 

 exhausted to the stratification point. During the.se operations 

 the platinum terminals of one of the vacuum tubes were heated 

 to full redness and the current was kept on both tubes for some 

 hours to drive off occluded gases. 



H'l. 



Fig. s. 



Finally, the second generator was sealed off and hydroger* 

 used from the remaining generator. After much washing out 

 with hydrogen at the ordinary pressure, exhau.stion and re-filling 

 were continued, and finally the reservoir K was filled, both taps, 

 H and I, being closed. The lubes were highly exhausted to the 

 non-conducting point, and tap i opened and then closed, so as 

 to introduce a little hydrogen. H was then opened and again 

 closed, so as to equalise the pressure in i, and exhaustion pro- 

 ceeded to the stratification point. At first the strata were 

 irregularly coloured with a suspicion of blue on one face, but as 

 the operations just described were continued, the blue faces 

 disappeared, the stratifications assumed a pure pink hue and 

 showed the hydrogen spectrum alone ; no mercury was detected 

 in any part of either tub^ 



From the first to the eighth filling the sirata were pink with 

 a trace of slaty blue colour on the faces next the negative )>ole. 

 From the tenth filling the blue faces disappeared, and after the 

 twentieth filling no tr,iceof blue could be seen ami the spectrum. 

 of hydrogen alone was visible. 



On examining Ihe speclra of the stratified gas in the two 

 tubes, each showed strongly the line spectrum of hydrogen ; but 

 while the spectrum in the platinum-poled lube showed pure 

 red, blue and green lines on a black ground, ihat in the 

 aluminium-poled lube showed in addition the fainter hydrogen, 

 line spectrum in Ihe yellow and orange. This result may be 

 due to Ihe greater surface exjjosed by the aluminium poles ; it 

 was not furlher examined. 



Having at last succeeded in getting hydrogen free from- 

 mercury, experiments were instituted to verify the inference that 



NO. 1686. VOL. 65I 



