188G.] NEW YORK ACADEMY OF SCIENCES. 191 



tliis i)l;ice they are superfluous, for we deal witli results rather 

 than with methods. Being ignorant of the "critical point" for 

 oxygen, both experimenters employed a much greater pressure 

 than necessary. 



Since the initial successes, the problem of liquefying the quon- 

 dam permanent gases has been successfully attacked by several 

 experimenters, especially by Wroblewski and Olzewski, whose 

 names indicate their nationality." By em])loyingIi([uid ethylene 

 (which boils i/i vacuo as low as —150° C. [ — 238° F.]) as a means of 

 cooling the gases under pressure, botli oxygen and nitrogen, as 

 well as atmospheric air have been liquefied at very moderate pres- 

 sures. 



Among the interesting results obtained are the following: at 

 — 10-2C. ( — 152^F.), chlorine forms orange-colored crystals; at 

 -115° C. (-175° F.), hydrochloric acid is" a solid; at -118° C. 

 ( — 180°F.), arsenetted hydrogen forms white crystals; at —129° 

 C. (-2' 0°F.), ether solidifies; at -130° C. (-202° F.), absolute 

 alcohol solidifies; at -184° C. (-299° F.), oxygen boils; at - 

 191.2° C. (-312° F.), air boils; at -205° 0. (-337° F.), air 

 boils in vacuo. These extraordinary temperatures were measured 

 by means of an hydrogen thermometer, and by a thermo-pile. 

 The lowest temperature measured (to date) is —225° C. (—373° 

 F.), which was reached by reducing the pressure of solid nitrogen 

 to 4 mm. mercury" (Olzewski). Further noteworthy results are 

 as follows: nitrogen was obtained in "snow-like crystals of re- 

 markable size; " the liquefaction of air has been so conducted as 

 to obtain two distinct liquids separated by a perfectly visible 

 meniscus (Wroblewski)," and, finally, when hydrogen was sub- 

 jected to between 100 and 200 atmospheres pressure in small 

 glass tubes surrounded, by oxygen boiling in vacuo, it condensed 

 to colorless drops. 



These noteworthy results are triumphs of physics rather than 

 of chemistry, but no review of chemical pi'ogress can afford to 

 omit them; their bearing on the molecular theory of matter 

 justifies the space given them. It seems probable, moreover, 

 that every known substance on the face of the. earth will be even- 

 tually obtained in solid form by the mere withdrawal of heat. At 

 these low temperatures the chemical activity of bodies is greatly 

 lessened or ceases, but additional observations must be made on 

 this point before attempting generalizations. 



Experiments of the character described demand great resources 

 and are not devoid of danger; those conducting them will be re- 

 warded by undying fame. 



(15.) The progress of chemistry in its more material aspects is 

 characterized by the improved and economic production of 

 known substances, by the discovery and manufacture of entirely 



