Page:Popular Science Monthly Volume 47.djvu/539

Rh pressure at —187º. Its critical and boiling points lie between those of oxygen and nitrogen, nitrogen having the lowest of the three.

Argon is four tenths heavier than nitrogen, and much more soluble in water. As already stated, and as is evident from the methods employed for its preparation, argon is more inert than nitrogen; so great is its chemical indifference, that all attempts to bring about reactions with even the most active substances at high temperatures have thus far proved abortive. It is unaffected by phosphorus or sulphur at red heat; sodium and potassium may be distilled in it without loss of their metallic luster; it is unaltered by fused and red-hot caustic soda or niter; aqua regia and other wet oxidizing and chlorinating agents are entirely without action; and it resists the attack of nascent silicon and boron.

Though thus unique in its chemical inactivity, it would be premature to conclude that argon may not form compounds under conditions yet untried, and that it is an absolutely "idle" and useless thing. Prof. Roberts-Austen suggests that it may possibly play a part in certain metallurgical operations in which air is largely employed. In making Bessemer steel, for instance, not less than one hundred thousand cubic feet of air are blown through each charge of metal for the purpose of removing the carbon, silicon, phosphorus, and other impurities. In this air there must be over one thousand cubic feet of argon. Now, Prof. Roberts-Austen has found by experiment that the nitrogen which can be pumped out of Bessemer-blown metal, and which is twice the volume of the metal, contains little or no argon; and the question arises, whether the argon may not have united with the iron, as nitrogen undoubtedly does, and confer upon Bessemer steel some of the peculiarities which distinguish it from other steel. It is, of course, possible and perhaps more likely that the argon passes through the molten metal without combining with it; but the suggestion is an interesting one, and well worth experimental examination.

Further, it may prove that argon is in some way taken up by plants, and contributes in an important manner to their nourishment and growth; although the attempts to extract argon from vegetable and animal substances have thus far yielded only negative results. As is well known, plants are unable to take nitrogen directly from the air, but obtain it from nitrogenous compounds which are absorbed in solution by their roots. The air is, however, the original source of these compounds, as well as of all