138 NEW RESEARCHES ON LIQUID AIR. 



bands are disposed to take over the problem from tbe scientific 

 researcher." 



Solid air. — As Professor Olszewski has recently alleged that air does 

 not solidify at the lowest pressures, * the author's former experiments 

 were repeated on a larger scale. If a liter of liquid air is placed in a 

 globular silvered vacuum vessel and subjected to exhaustion, as much 

 as half a liter of solid air can be obtained and maintained in this con- 

 dition for half an hour. At first the solid is a stiff, transparent jelly, 

 which, when examined in the magnetic field, has the liquid oxygen 

 drawn out of it to the poles. This proves that solid air is a nitrogen 

 jelly containing liquid oxygen. This statement was made in a paper 

 "On the refraction and dispersion of liquid oxygen, and the absorption 

 spectrum of liquid air" (Professors Liveing and Dewar), published in the 

 Philosophical Magazine for September, 1895, yet Professor Olszewski, 

 in 1896, 2 is declaring "that Professor Dewar has stated that liquid air 

 solidifies as such, the solid product containing a slightly smaller per- 

 centage of nitrogen than is present in the atmosphere. My experiments 

 have proved this statement to be incorrect." The Cracow professor may 

 well have the satisfaction of correcting a statement which was never 

 made by me. He seems also to forget that in 1893 (Proceedings Eoyal 

 Institution, "Lecture on liquid air"), it is distinctly stated that "all 

 attempts to solidify oxygen by its own evaporation have failed." Solid 

 air can only be examined in a vacuum or in an atmosphere of hydrogen, 

 because it instantly melts on exposure to air cooled to the temperature of 

 its boiling point, giving rise to the liquefaction of an additional quantity 

 of air. It is strange to see a mass of solid air melting in contact with 

 the atmosphere, and all the time welling up like a kind of fountain. The 

 apparatus shown in fig. 2, Plate III, is well adapted for showing the direct 

 liquefaction of the air of a room and its solidification. A large vacuum 

 vessel, G, is mounted on a brass stand containing another smaller vessel, 

 B, of the same kind. By means of the two cocks, C and D, either the 

 large vessel Gr or the bulb B can be connected to the air-pump circuit. 

 Liquid oxygen is placed in A, which can, by opening the stopcock D, be 

 cooled to — 210° by exhaustion. If the stopcock O is shut and a baro- 

 metric gauge is joined on at F, the dropping of the liquid air from the 

 outside of A will go on even at as low a pressure as 4 inches of mercury; 

 which is equivalent to saying that this apparatus would liquefy air if 

 taken by a balloon 10 miles high. If F is now opened, giving a supply 

 of air at atmospheric pressure, the cup B soon fills with liquid air. 

 Unless the air supply is passed over soda lime and strong sulphuric, 

 the liquid is always turbid from the presence of ice crystals and solid 

 carbonic acid. Now, on shutting F and opening C the air in B is placed 

 under exhaustion and soon solidifies to a jelly-like mass. When the 

 vacuum is about 14 mm. then the temperature of the solid air is — 232° 

 by the platinum resistance thermometer, or — 216° C. On allowing 

 the air to enter, the solid instantly melts and more liquid air is formed. 



Phil. Mag., Feb., 1895. -<See Nature, Aug. 20, p. 378. 



