ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 17 



contained phosphoric anhydride, and (a) soda-Iinie. The tube D coinimuiicated 

 with a hai'd-glass tube, J^], heated over a long-flame l)ui-ner; it was partly filled 

 with metallic copper, and partly with copper oxide. Tiiis tube, as well as the 

 tube F, filled with magnesium turnings, was connected to the di'ying tube with 

 india-rubber. The g;s then entered G, a graduated reservoir, and the arrangement 

 H permitted the i-emoval or introduction of gas fiom oi- into the ai)paratus. The 

 gas was gi'adually transferred from the gas-holder to the tube C, and [)assed back- 

 wards and forwards over the I'ed-hot magnesium until about 200 cubic centimetres 

 were left. It was necessary to change the magnesium tube, which was made of 

 smaller size than formerly, sevei-al times during the operation. This was done by 

 turning out the long-flame bui'nei-s and pumping off all gas in the horiz<iiital tubes 

 by means of the Sprengel's pu!np. This gas was carefully collected. The mag- 

 nesium tube was then exchanged for a fresh one, and after aii' had been exhausted 

 from the apparatus, nitrogen was introduced from the reservoir. Any gas evolved 

 from the magnesium (and appai-ently there was always a trace of hydrogen, either 

 occluded by the magnesium, or j^roduced by the action of aqueous vapor on the 

 metal) was oxidized by the copper oxide. Had oxygen been present, it would 

 have been absorbed by the metallic copper, but the copper preserved its red 

 appearance without alteration, whereas a little copper oxide was reduced during 

 the series of operations. The gas, wdiich had been removed by pumping, was 

 I'eintroduced at H, and the absorption continued. 



The volume of the gas was thus, as has been said, reduced to about 200 cubic 

 centimetres. It ^vould have been advisable to take exact measurements, but, un- 

 foi-tunately, some of the original nitrogen had been lost through leakage ; and a 

 natural anxiety to see if there was any unknown gas led to pushing on operations as 

 quickly as possible. 



The density of the g;is was next determined. The bulb or globe in which the 

 gas was weighed was sealed to a two-way stopcock, and the weight of distilled and 

 air-fi'ee water filling it at 1 7°.l 5 was 162.654 gi-anmies, cori'esponding to a capacity of 

 162.843 cubic centimetres. The shrinkage on removing air completely was 0.0212 

 cubic centimetre. Its weight when empty should therefore be increased by the 

 weight of that volume of ail-, which may be taken as 0.000026 gramme. This 

 coi'rection, howevei", is pei'haps hardly worth a|)[)lying in the present case. 



The countei'poise was an exactly similar bulb, of equal capacity, and weighing 

 about 0.2 gramme heavier than the empty globe. The balance was a very sensitive 

 one by Oei'tling, which easily measui'ed one-tenth of a milligramme. By the 

 process of swinging, one-hundredth of a milligramme would be determined with 

 fair accuracy. 



