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PKOFESSOR H. B. DIXON AND MR. E. C. EDGAR 



lessening the flow of -gas through a tube," improvements have been made which 

 seemed to us to justify the use of one for regulating the flow of hydrogen from the 

 palladium bulb. The tap B, fig. 2, was made with a long barrel with its bearings 



B 



Fig 2. The palladium vessel. 



ground to the sheath for a length of 30 millims. The barrel forms a portion of an 

 elongated cone, its diameter at the wider end being 10 millims., and at the narrower 

 end 8 millims. The bore of the tap is inclined so that one opening is 10 millims. 

 above the other. The sheath of the tap ends in a closed bulb below and a cup 

 above. 



The method of lubricating and fixing the tap was as follows : After thorough 

 cleaning and drying, the bulb b of the tap was filled with dry mercury to such a 

 height that the barrel of the tap, when placed in position, just touched its surface. 

 The mercury was then gently heated until it filled the whole bulb. The lubricant 

 glacial phosphoric acid was melted and carefully rubbed over the barrel, which was 

 placed in position, turned several times to ensure equal distribution of the lubricant, 

 and then pressed firmly into the sheath whilst the bulb b containing the mercury 

 was cooled. The bulb now contained no air, but the cooling resulted in the 

 production of a partial vacuum, which kept the tap firmly fixed. We have tested 

 this tap by a pump and found it to remain perfectly gas-tight. All the other taps 

 used in the apparatus with the exception of the chlorine tap were made and used 

 in the same way. We are indebted to the skill of the University glass-blower, 

 OTTO BAUMBACH, for the accurate grinding of these taps, and for the joints by 

 which he succeeded in fusing hard Jena to soft glass. 



It was of course essential that the weight of the palladium bulb should be most 

 accurately determined before and after the combustion of its charge of hydrogen. 

 To avoid change of volume the bulb was made of a hard Jena glass which 

 preliminary hydrostatic weighings showed not to alter when heated to dull redness 

 and cooled. The charged palladium bulb was heated and cooled alternately to 



