ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 19 



Temperature 19.12 C. Barometric pressure 749. 8 mm. (corr.) 

 Difference read on gas-holder and tube ::25.25 mm. (corr.) 

 Actual pressure, 524.55 mm. 



Weight of 162.843 eul)ic centimetres of gas 0.17913 gramme. 



Weight of I litre at o" and 760 mm. pressure >.7o54 " 



Density 19.086 " 



This gas is accordingly at least 19 times as heavy as liytlrogen. 



A portion of the gas \\as then mixed vvitli o.xygen, and submitted to a rapid 

 discharge of sparks for four houi's. It contracted, and on absorbing the excess of 

 oxygen with pyrogallate of potas.sium the contraction amounted tt) lo.-i p^r cent of 

 the original volume. The question theo arises : If the gas contained 15.4 per cent 

 of nitrogen of density 14.014: and 84.6 per cent of other gas, and if the density of 

 the mixture were 19.086, what would be the density of the other gas ? Calculation 

 leads to the number 20.0. 



A vacuum-tube was filled with a specimen of the gas of density 19.086, and it 

 coukl not be doubted that it contained nitrogen, the bands of which were distinctly 

 visible. It was probable therefore that the true density of the [lure gas lay not 

 far from 20 times that of hydrogen. At the same time many lines were seen which 

 could not be recognized as belonging to the spectrum of any known substance. 



Such were the i)relimiuary experiments made with the aid of magnesium to 

 separate from atmosphei'ic nitrogen, its dense constituent. The methods adopted 

 in preparing large quantities will be subsequently de.scril)ed. 



6. Proof of the Presence of Argon in Air, by Means of Atmolysis. 



It has already (§ 2) been suggested that if "atmospheric nitrogen" contains 

 two gases of different densities, it should be possible to obtain direct evidence of 

 the fact by the method of atmolysis. The present section contains an account of 

 carefully conducted experiments directed to this end. 



The atmolyser was prepared (after Graham) by combining a number of 

 "church-warden" tobacco pipe.s. At fii'st twelve pipes were used in three groups, 

 each group including four pipes connected in series. Tlie three groups were then 

 connected in parallel, and placed in a large glass tube, closed in such a way that a 

 partial vacuum could be maintained in the space outside the pipes by a water 

 pump. One end of the combination of pipes was open to the atmosphere, or rather 

 was connected with the interior of an open bottle containing sticks of caustic alkali, 

 the object being mainly to dry the air. The other end of the combination was 

 connected to a bottle aspirator, initially full of water, and so ai-i-auged as to draw- 

 about 2 per cent of the air which entered the other end of the i)ipes. The gas col- 

 lected was thus a very small propoition of that which leaked thi'ough the pores of 



