458 SCIENTIFIC RECORD FOR 1884. 



glass vessel with an opening at its lower part, whicli allows a part of the 

 liqnid in the instrument to flow out as the vapor in the upper portion 

 expands. By means of a weighing apparatus the pressure of the in- * 

 closed vapor is ascertained. The results seem to be satisfactory. ( Wied 

 Ann., XXI, 406; Am. J. Sci., November, 1884, III, xxviii, 390.) 



Meunier has modified the apparatus of Crafts and Meyer so as to ob- 

 tain with it, under greatly reduced pressure, the vapor density of certain 

 additional products of benzene which decompose at their boiling point 

 under the ordinary pressure. The results given agree closely with 

 theory. {C. B., xcviii, 12G8, May, 1884.) 



Clark has described an apparatus for the purification of mercury by 

 distillation, which differs from those hitherto suggested chiefly in being 

 supplied with the mercury to be distilled from a movable reservoir in 

 the form of a constant-level regulator, the raising of which fills the dis- 

 tiller with mercury, thus rendering unnecessary a Sprengel pump to 

 start the operation. The apparatus described will distill about two 

 pounds of mercury in an hour. {Fhil. Mag., January, 1884, V, xvii, 24.) 



Many experiments have been made on the liquefaction of the so-called 

 permanent gases. Wroblewski has XJroduced liquid oxygen in such 

 quantities as to use it as a refrigerating agent. When liquefied in large 

 quantity and allowed to evaporate briskly by the sudden removal of the 

 pressure, it does not solidify like carbon dioxide, though it deposits a 

 crystalline residue. Hitherto he has not found it possible to obtain 

 oxygen in a stable liquid condition under the pressure of one atmos- 

 phere. Hence the objects to be cooled must be placed in the apparatus, 

 which is then filled with the liquid oxygen. By means of a thermo- 

 electric apparatus, controlled by a hydrogen thermometer between 100° 

 and —130°, the author estimates the temperature produced by boiling 

 oxygen at —186°. When nitrogen is compressed, cooled in boiling 

 oxygen, and then slightly released from pressure, it solidifies and falls 

 like snow, in crystals of remarkable size. {Phil. Mag., February, 1884, 

 V, xviii, 158; Am. J. Sci., April, 1884, III, xxvn, 319.) 



Dewar, in a lecture at the Eoyal Institution, produced and experi- 

 mented with 1.5 c. c. of liquid oxygen, prepared by an apparatus of great 

 simplicity. In an iron reservoir oxygen is compressed to 150 atmos- 

 pheres. A copper tube, on which is a manometer, connects this reser- 

 voir with a glass tube 5""" diameter and 3'"'" thick, in which the lique- 

 fied gas collects. This is inclpsed in a glass tube containing the liquid 

 ethylene, solid carbon dioxide, or liquid nitrogen monoxide, which is to 

 be boiled in vacuo as the refrigerant. Outside of this is a larger tube, 

 through which the cold vapors pass on their way to the air-pump. When 

 the pump has reduced the pressure to 25""", the ethylene has a temper- 

 ature of about —140° ; and then a pressure of between 20 and 30 at- 

 mospheres is suificient to produce liquid oxygen in the tube. When 

 solid CO2 is used, a temperature of —115° is obtained ; and with liquid 

 N2O, one of —125°. As the critical point of oxygen is —113°, both 



