PHYSICS. ^»C)o 



respectively, to two, seven, and twelve molecules of water; of two hy- 

 drates of sodium borate, with five and ten molecules of water; of two 

 hydrates of sodium carbonate, with one and ten molecules ; while in 

 sodium sulphate all the combined water constitutes only a single hy- 

 drate. {Wied. An7i., xxiii, 607 ; J. Phys., November, 1885, II, iv, 521.) 



Klobukow has contrived two new forms of apparatus for measuring 

 vapor densities, the one for substances of low the other for substances 

 of high boiling point. The latter, which is the more novel, has the form 

 of an areometer of constant volume, containing a cavity for the vapor, 

 the volume being deduced from the weight required to restore the 

 level. The areometer is floated in mercury, the temperature of which 

 is raised so as to volatilize the substance used. ( Wied. Ann., xxii, 493 ; 

 J. Phys., April, 1885, II, IV, 177, 179.) 



In consequence of the very considerable loss in preparing solid car- 

 bon dioxide, Cailletet proposes the use of a hollow cylinder closed at bot- 

 tom, and having a cover attached by a bayonet catch, through which 

 cover an inclined tube passes to within a few millimeters of the bottom 

 of the cylinder. Through the middle of the base a larger tube passes 

 which serves for a handle and also for the escape of the gas. It rises 

 nearly to the top of the box and is perforated with holes. The whole 

 apparatus is made of vulcanite. Experiments show that 65 grams of 

 snow are obtainable from 200 grams of the liquid carbon dioxide blown 

 in through the inclined tube. {J. Phys., March, 1885, II, iv, 122.) 



Cailletet has succeeded in obtaining by the use of liquid ethylene a 

 temperature sufficiently low to liquefy oxygen completely. The com- 

 plete apparatus, constructed by Ducretet, is so well arranged that the 

 production of liquid oxygen is an easy lecture-room experiment. The 

 steel cylinder containing the liquid ethylene is supported with its axis 

 vertical, its mouth being downward. To this a cojjper worm 3™"" or 4™™ 

 in diameter is attached, closed at the lower end by a screw plug. On 

 cooling this worm to— 70° in a bath of methyl chloride, the ethylene 

 within it has only a feeble tension and flows out without much loss when 

 the screw plug is opened. The liquid ethylene is received in a narrow 

 tube of thin glass placed within a larger vessel containing dry air. It 

 is necessary now only to accelerate its evaporation by passing through 

 it a rapid current of air or hydrogen, also cooled in the methyl chloride 

 bath, in order to see the oxygen compressed in a glass tube immersed 

 in the ethylene condense into a clear colorless liquid having a sharply- 

 defined meniscus. A hydrogen thermometer showed the temperature 

 of the ethylene to be-123o. (C. E., c, 1033; J. Phys., July, 1885, II, rv, 

 293; Nature, October, 1885, xxxii, 584; Am. J. Sci., July, 1885, III, 

 XXX, 73.) 



Olszewski has measured the density and the expansion coefficient of 

 liquid oxygen. A small reservoir of glass 1-4 <>• ''• in capacity was filled 

 with liquid oxygen, cooled to —139^ by the evaporation of liquid ethyl- 

 ene and maintained at a pressure of 40 atmospheres. The oxygen was 

 then allowed to resume the gaseous state and from the volume of this 



