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gerator space F by means of the tube Y opening below mercmy. 



g. In protecting the different parts against heat from the sur- 

 rounding atmosphere, care has been taken that those surfaces of 

 which the temperature might fall below the boiliiig point of air and 

 which are not sufficiently protected by the conduction from less 

 cooled parts, should not come into contact with air but only with 

 hydrogen. The refrigerator vessel F, for instance, is surrounded 

 with the hydrogen which fills the cases U and V; hydrogen is also 

 to be found in the space between the vacuum glass L and the wall 

 of the case V; and lastly a side tube V^^ and V^^ branches off 

 from the case V in order to surround with hydrogen the double-walled 

 siphon tube N^^, N^^^ and the double walled cock N^, iV^soi- 



The new-silver case V, from which the vacuum glass L is insulated 

 by laj^ers of paper V^^ and the refrigerator vessel F by a layer of 

 flannel, and in the same way the new-silver case f7, are further pro- 

 tected from conduction of heat from outside by separate wrappings 

 of capoc T^gi, packed within a card-board cover Y^^ pasted together. 

 To prevent condensation of water vapour, the air in this enclosed space 

 communicates with the atmosphere by means of a drying tube t.dr 

 filled with pieces of sodium hydroxide, as in the ethylene- and 

 methyl chloride regenerators (comp. above sub b). 



The air-tight connection between the case U and the case Y is 

 effected by the India rubber ring Ua, which fits on the glass and 

 on the strengthened rims JJ^^ and Fso of the new-silver cases. India 

 rubber of somewhat larger dimensions can only be used for tightening 

 purposes when it is not cooled. In this case the conduction along the 

 new-silver wall, which is insulated from the vacuum glass by layers 

 of paper, is so slight that the ring-shaped strengthened rims remain 

 at the ordinary temperature and the closure can be effected by a 

 stout stretched India rubber ring. When the India rubber is only 

 pressed on the glass this closure is not perfectly tight; therefore the 

 whole connection is surrounded with an atmosphere of almost pure 

 hydrogen, which is obtained and maintained by the India rubber ring 

 Uc, which fits tightly on U^ and Y^ and which is filled with hydrogen 

 under excess of pressure tiirough the cock Ud. Thanks to the small 

 conduction of heat of new-silver no cooling is to be feared for the 

 connections of Y^^ and U^^ no more than for the packings of the 

 cocks il/3 and N^. 



h. The cases Y and U are joined and form one firm whole by 

 the three rods Uh with 1 he screw-fastenings f/g( and F^^. The vacuum 

 glass E^, held by the India rubber ring Ua, rests with a wooden 

 ring E^ and a new-silver cylinder f/,i against the refrigerator vessel F. 



