524 THE POPULAR SCIENCE MONTHLY. 



planation then occurred, that the lightness of the " chemical" 

 nitrogen was due to a partial dissociation or breaking up of the 

 molecules of the gas into single atoms under the conditions of its 

 preparation. This, too, was negatived by experiment. One or 

 the other of the gases must be a mixture, containing an ingredi- 

 ent much heavier or much lighter than ordinary nitrogen. To 

 suppose a lighter ingredient mixed with the chemical nitrogen 

 required the existence of two kinds of nitric acid, which was out 

 of the question. " The simplest explanation in many respects was 

 to admit the existence of a second ingredient in air from which 

 oxygen, moisture, and carbon dioxide had already been removed." 



This explanation was put to the test by an attempt to isolate 

 the suspected gas, with the result that by two entirely distinct 

 methods a new substance was obtained from air. 



One of these methods was that of Cavendish, already de- 

 scribed. Air confined over dilute alkali is subjected to the ac- 

 tion of electric sparks, while oxygen is added from time to time 

 until, with an excess of oxygen present, no further absorption 

 occurs. The oxygen is then removed by alkaline pyrogallate, and 

 argon is left. 



The second method for the separation of argon is based on the 

 fact that red-hot magnesium unites with nitrogen, forming a non- 

 volatile compound. Air from which moisture and carbon dioxide 

 have been removed is freed from oxygen by passing it over heated 

 copper, and then from nitrogen by means of magnesium turnings 

 at a red heat. The removal of the last portions of nitrogen is a 

 tedious operation, requiring some two days. The residual gas is 

 pure argon. 



The gas obtained by both of these methods is the same, and its 

 behavior proves conclusively that it is a new substance. Prof. 

 Crookes finds that it gives two spectra, according to the strength 

 of the induction current, one characterized by red and the other 

 by blue lines ; and testifies that he has " found no other spectrum- 

 giving gas or vapor which yields spectra at all like those of 

 argon"; and that "as far, therefore, as spectrum work can de- 

 cide, the verdict must, I think, be that Lord Rayleigh and Prof. 

 Ramsay have added one, if not two, members to the family of 

 elementary bodies." 



The behavior of argon at low temperatures and under high 

 pressures has been examined by Prof. Olszewski, of Cracow, who 

 is well known for his researches on the liquefaction of air and 

 other gases, its critical temperature that is, the temperature at 

 which its liquefaction under pressure first becomes possible is 

 121 C, and at that point it is condensed to a liquid by a pressure 

 of 50"G atmospheres. Liquid argon becomes an icelike solid at a 

 still lower temperature, melts at 189*6, and boils under ordinary 



