C,OA SCIENTIFIC RECORD FOR 1885. 



latter its weight was calculated. The density thns obtained was 0-8787 

 at — 139-130. The expansion coefficient was 0-01706. Moreover the 

 author finds that liquefied chlorine congeals at —102° and that hydrogen 

 chloride is solid at —115-7° and fuses again at — 112-3°. Hydrogen 

 arsenide freezes at — 118-9° and melts at —113-5°. Silicon fluoride 

 is solid at —102°. Ethyl ether freezes at —129°. Methyl alcohol has 

 the consistence of oil at —102° and of butter at —115° ; it then passes 

 gradually into the solid state, which is reached at —134°. {Ber. Ak. 

 Wien, 1884, 72 ; J. Phijs., April, 1885, II, iv, 184.) 



Wroblewski has described in detail the apparatus which he uses for 

 the liquefaction of gases and has given the results of his comparisons of 

 the hydrogen thermometer with the thermo-electric couple. The criti- 

 cal temperatures for nitrogen, carbon dioxide, and oxygen he finds to be 

 —145°, —141°, and —118°, respectively ; and the critical pressures 

 33-6, 35, and 50 atmospheres. The boiling points under a pressure of 

 740mm^ are —193°, —190°, and —181-5° The lowest temperatures which 

 he has observed are — 200-4° for oxygen under a pressure of 2"'°, -200° 

 for nitrogen at 4-2''°», and for carbon monoxide —201-6° at 4""^. Both 

 nitrogen and carbon monoxide solidify at these temperatures. {Ber. 

 Ah. Wien, March, 1885 ; J. Phys., July, 1885, II, iv, 316.) 



In hygrometry several papers have appeared. Hazen has studied the 

 psychrometer and has compared its indications with those of the con- 

 densing hygrometer. {Am. J. Sci., December, 1885, III, xxx, 435.) . 



Bourbouze has suggested two new modifications of the hygrometer. 

 One of these is based on the production of the colored rings seen round 

 a source of light when viewed through a glass i)late on which vapor 

 begins to condense. A small rectangular tube has holes on opposite 

 faces closed by very thin glass plates. A very sensitive thermometer 

 is used, dipping only very slightly into the liquid. On causing a cur- 

 rent of air over the liquid surface, either by aspiration or otherwise, 

 the whole is cooled and dew is deposited on the glass. By placing the 

 apparatus between the eye and a luminous point these concentric rings 

 are readily observed and the temperature noted. The other instrument 

 is similar but has a metallic envelope, the temperature of which is de- 

 termined by the thermometer. {J. Phys., September, 1885, II, IV, 425; 

 Phil. Mag., August, 1885, V, xx, 220.) 



Sire has also suggested two new types of condensing hygrometers, 

 in both of which the deposit of dew is observed on a cylindrical or 

 plane brilliant surface. The reservoir in the first type is a cylindrical 

 tube of thin polished metal, the ends of which are insulated in the in- 

 terior by two pieces of ebonite, so that the volatile liquid is in contact 

 with the metal only over a middle zone a centimeter broad. In the 

 second the reservoir is entirely of ebonite, traversed laterally by a cir- 

 cular aperture closed by a thin metal disk, polished on the inside. The 

 surfaces are metallic palladium. {Phil. Mag., November, 1885, Y, xx, 

 468.) 



