24 



ARGON. A NKW CONSTITUKNT OV THE ATMOSPHERE. 



On tlie wliole, tlie use of iron tul)fs is not to In- ivcMiMiieucleil, owing to the 

 (lillifiilty in cleaning them, an«l the i»ossible loss through their permeability to 

 argon. There is no such risk of k)ss with glass tubes, but each operation lequires 

 a new tube, and the cost of the glass is considerable if much nitrogen is to be 

 ab.sorbed. TuV)es of porcelain were not tried ; but they are hardly likely to suc- 

 ceed, for the glaze in the interior would certainly be destroyed by the action of the 

 red-hot magnesium, and the i-oiighening of the surface would render tin-in as difh- 

 cult to emjtty and refill as the iron tubes were found to V)e. 



By these processes 157 litres of "atmospheric nitrogen" were reduced in 

 volume to about 2.5 litres in all of a mixture of nitrogen and argon. This mixture 

 was afterwards circulated over red-hot magnesium in order to remove the last 

 portions of nitrogen. 



As the ai)paratus employed for this purpose proved very convenient, a 

 full description of its construction is here given. A diagram is shown in Fig. 4 



Fig. 4- 



which sufficiently explains tin- anangement of the api)aiatus. A is the circidator. 

 Itconsists of a sort <<[' Spicuucrs pump (a), to w liich a supply of mcicury is ;idniitlc<l 

 from a small leservoir (//). This mercury is delivered into a gas-separator (c), and 

 the mercury <»verflows into the reservoir (d). When its level rises, so that it 

 blocks the tube (/), it ascends in pellets or pistons into a reservoir (e) which is 

 connected through {g) with a water-pump. The mercury falls into (Ji), and again 

 passes down the Sprcngfl-tiibe (a). No attention is therefore rerpiired, for the 



