1895.] Argon, a new Constituent of the Atmosphere. 283 



sorbed by passing it over fused red-hot caustic soda, or soda-lime 

 heated to bright redness ; it passes unaffected over fused and bright 

 red-hot potassium nitrate ; and red-hot sodium peroxide does not com- 

 bine with it. Persulphides of sodium and calcium are also without 

 action at a red heat. Platinum black does not absorb it, nor does 

 platinum sponge, and wet oxidising and chlorinating agents, such as 

 nitro-hydrochloric acid, bromine water, bromine and alkali, and 

 hydrochloric acid and potassium permanganate, are entirely without 

 action. Experiments with fluorine are in contemplation, but the 

 difficulty is great ; and an attempt will be made to produce a carbon 

 arc in the gas. Mixtures of sodium and silica and of sodium and 

 boracic anhydride are also without action, hence it appears to resist 

 attack by nascent silicon and by nascent boron. 



XYT. General Conclusions. 



It remains, finally, to discuss the probable nature of the gas, or 

 mixture of gases, which we have succeeded in separating from 

 atmospheric air, and which has been provisionally named argon. 



The presence of argon in the atmosphere is proved by many lines 

 of evidence. The higher density of "atmospheric nitrogen," and 

 the uniformity in the density of samples of chemical nitrogen pre- 

 pared from different compounds, lead to the conclusion that the cause 

 of the anomaly is the presence of a heavy gas in air. If that gas 

 possess the density 20 compared with hydrogen, " atmospheric nitro- 

 gen " should contain of it approximately 1 per cent. This is, in 

 fact, found to be the case. Moreover, as nitrogen is removed from 

 air by means of red-hot magnesium, the density of the remaining 

 gas rises proportionately to the concentration of the heavier con- 

 stituent. 



Second. This gas has been concentrated in the atmosphere by diffu- 

 sion. It is true that it cannot be freed from oxygen and nitrogen 

 by diffusion, but the process of diffusion increases, relatively to 

 nitrogen, the amount of argon in that portion which does not pass 

 through the porous walls. This has been proved by its increase in. 

 density. 



Third. As the solubility of argon in water is relatively high, 

 it is to be expected that the density of the mixture of argon and 

 nitrogen, pumped out of water along with oxygen, should, after 

 the removal of the oxygen, exceed that of " atmospheric nitrogen." 

 Experiment has shown that the density is considerably increased. 



Fourth. It is in the highest degree improbable that two processes, 

 so different from each other, should manufacture the same product. 

 The explanation is simple if it be granted that these processes merely 

 eliminate nitrogen from an atmospheric mixture. Moreover, if, as 



x 2 



