AND KATIO Ol-' TIIKIK ATOMIC \VK,I( !1 ITS. 



85 



tube with tht- 'ro('[ilci- puiiip was iiiddiliud so ;is to coiituiu the t;lass sti>[ipei' l>, 

 j^iduikI so as to Ht into its seat, and attaelied to a loni:,' i^'hiss rod whieli continued 

 downwards about '.Mi centimetres witliiii tlie glass tube c <j. The end of this tube 

 Avas prolonged in the I'ubber tube </, which was attached also to the rod, so that 

 the space between them could be Hlle<l with mercury. Tlie elasticity of the rubber 

 tube permitted the stopper to be I'aised and lowered ; the mercury prevented leak- 

 age. It is obvious tliat when this sto[)per is forced into its seat, and the vacuum 

 below it is tilled with mercury, gas cannot pass from the globes into the space 

 beh)\v tlie [ilug, provided the pressure of the mercury upwards is kept gi'eater than 

 that of the iras downwards. 



4. — DKXsrrv ok kmcoiuolytic (JAs. voi/i'a.mktp;k foij ntoiniciNc; ano WKUiHiNG. 



A voltameter to produce electrolytic gas, and to make it perfectly dry, and to 

 do it at the rate desired, without being too heavy or too bulky, took some pains in 

 constructing. Using five voltameters combined iu 

 one and couuected electrically iu series, it was deemed ' ^^ 



best to use a current of four amperes. The plati- fC ^ 

 num wires to conduct this current without undue ~~- — Nk., g ,' , < ,:, g .j^,. .y, fe i, 

 heating 1 found it somewhat difficult to introduce 

 into the glass of my apparatus without having them 

 afterwards crack. Several experiments were lost ii 

 this way ; after the passage of the curi'ent fen- four 

 hours, some minute crack around a wire wouhl leak 

 at the rate of half a milligramme an hour. Gradu- 

 ally the faulty joints wei-e made good, and the ap- 

 paratus worked, without failure till a heedless 

 plumber knocked a brick through the wall, without 

 even looking to see what damage might be caused, 

 and crushed, it into a hundred fragments. 



Iu Fie 31 are shown five tubes 2. 5 centimetres iu 

 diameter, having platinum wires as seen in section at i'"'^-- ji.-Voitameic. for producing and 



^ ■*■ weighing mixed gases. 



in II. To these was connected a tube filled with phos- 



pliorus pentoxide, and also a stopcock ending in a ground joint. Into the central 



tube was introduced a gauge to show the pressui'e of the gas in the voltameter ; the 



gauge was filled with gas to the desired point (having being filled with liquid when 



constructed) by electi-olysis at the wires /_f, while the stopcock d was open to the 



atmosphere. 



