206 LORD RAYLEIGH AND PROFESSOR W. RAMSAY ON ARGON, 
Weight of 162°843 cub. centims. of gas . . . . . = 0'17913 grm. 
Weight of 1 litre at 0° and 760 millims. pressure. . 1:7054 _,, 
Density sow Ok Be Roan Bs 7, Sen POLO SG memos 
This gas is accordingly at least 19 times as heavy as hydrogen. 
A portion of the gas was then mixed with oxygen, and submitted to a rapid 
discharge of sparks for four hours in presence of caustic potash. It contracted, and 
on absorbing the excess of oxygen with pyrogallate of potassium the contraction 
amounted to 15°4 per cent. of the original volume. The question then arises, if the 
gas contain 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 
could not be doubted that it contained nitrogen, the bands of which were distinctly 
visible. It was probable, therefore, that the true density of the pure 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 preliminary experiments made with the aid of magnesium to 
separate from atmospheric nitrogen its dense constituent. The methods adopted in 
preparing large quantities will be subsequently described. 
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 GranHam) by combining a number of “ church- 
warden” tobacco pipes. At first twelve pipes were used in three groups, each group 
including four pipes connected in series. The 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 arranged as to draw about two per cent. of 
the air which entered the other end of the pipes. The gas collected was thus a very 
small proportion of that which leaked through the pores of the pipes, and should be 
relatively rich in the heavier constituents of the atmosphere. The flow of water 
from the aspirator could not be maintained very constant, but the rate of two per 
cent. was never much exceeded. ‘The necessary four litres took about sixteen hours 
to collect. 
