450 SCIENTIFIC RECORD FOR 1884. 



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

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

 expands. By means of a weighing aj^paratus the pressure of the in- 

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

 Ann., XXI, 466: Am. J. Sci., November, 1884, III, xxviii, 390.) 



Meunier has modified the ajjparatus of Ci afts and Meyer so as to ob- 

 tain with it, under greatly reduced i^ressure, 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, 1268, 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. {Phil. Mag., January, 1884, V, xvii, 24.) 



Many experiments have beenmadeon the liquefaction of the so-called 

 permanent gases. Wroblewski has produced 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, xxvii, 319.) 



Dewar, in a lecture at the Royal 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 inclosed 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 sufficient 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 



