592 SCIENTIFIC tiECORb FOR 



ton's theory, such rainfall is very small. {Jour. Phys., December. 1883, 

 II, II, 561.) 



Schwarz lias improved Meyer's vapor density method by nsing an or- 

 dinary combustion furnace in place of the special furnace of tbe former. 

 The substance is introduced into tbe heated combustion tube, which is 

 slightly inclined backward for tins purpose, and which has been previ- 

 ously tilled with nitrogen. The vapor expels the nitrogen, which is 

 collected over water and measured. As in Meyer's method, it is not 

 necessary to know the temperature of the furnace. (Ber. Berl. Chem. 

 Oes., xvi, 1051; Am. J. 8ci., September, 1883, III, xxvi, 234.) 



Pacinnotti has constructed a barometer containing water thoroughly 

 deprived of air above the mercury. This water retains the liquid state 

 even under a negative pressure. The mercury column stands at 903 

 millimeters above that in the reservoir, although the Fortiu barometer 

 shows a pressure of 700 millimeters only. The author gives several 

 experiments which show the necessity of a free surface in order lor 

 evaporation to take place. (J. Phys., November, 1883, II, n, 524.) 



Wroblewski and Olzewski have succeeded in liquefying oxygen, nitro- 

 gen, and carbon monoxide gases, by using a modified Cailletet's appa- 

 ratus, and employing the evaporation of liquefied ethylene to cool the 

 gas to be condensed, by which a temperature of — 13G° C. was obtained. 

 At this temperature a pressure of 20 atmospheres suffices to com- 

 pletely liquefy oxygen. It forms a colorless, transparent, very mobile 

 liquid, with a well defined meniscus. Nitrogen and carbon monoxide 

 arc more difficult to liquefy. At the temperature of —130° and under 

 a pressure of 150 atmospheres, the capillary tube shows no trace of 

 liquid. If, however, the pressure be rapidly though progressively di- 

 minished, not allowing it to fall below 50 atmospheres, both gases 

 liquefy, the meniscus being sharp and the liquids colorless and trans- 

 parent. They evaporate readily at this pressure and temperature, so 

 that to preserve them permanently a lower temperature is necessary. 

 The temperatures were observed with a hydrogen thermometer, as this 

 gas showed at —136° and under a pressure of 150 atmospheres no mist 

 on sudden expansion. Carbon disulphide became solid at —110°, and 

 liquefied again at —110°. Alcohol was viscous at —129°, and solidi- 

 fied at -130.5. (Wicd. Ann., xx, 243; C. K., xevi, 1140, 1225; Phil. 

 Mag., V, xvi, 75; J. Phys., November, 1883, II, n, 485.) 



Jamin has published some criticisms upon the ordinarily received 

 interpretation of the " critical point" of gaseous liquefaction. The facts 

 he concedes; but they have been inaccurately interpreted. He main- 

 tains that gases are liquefiable at any temperature whatever when the 

 pressure is sufficient, but a circumstance hitherto overlooked has pre- 

 vented the liquefaction from being seen. In Cagniard-Latour's experi- 

 ment, where a thick glass tube is one-half or two-thirds tilled with 

 water, sealed, and heated to 300° or 400°, the vapor increases indefi- 

 nitely in density and the liquid undergoes an increasing expansion, until 



