496 SCIENTIFIC RECORD FOR 1884. 



the number 0.89 for the density of oxygen, Wroblewski admits that the 

 figures 0.033 are not far from the trutli. On the other hand, gaseous 

 hydrogen reaches this same density, 0.033, at a low temperature, under 

 inconsiderable pressures; hence arises an optical difficulty in distin- 

 guishing the liquid from the gaseous hydrogen, a difficulty which prob- 

 ably prevented Wroblewski from reproducing Cailletet's experiment on 

 hydrogen. The analogy between the phenomenon described and those 

 presented by oxygen permit the supposition that the temperature nec- 

 essarj" for the complete liquefaction of hydrogen is not far from that 

 which maj^ be obtained by means of boiling oxygen. {Comptes rendus 

 xoviii, January 28, 1884.) 



Boiling Point of Hydrogen. — Dr. Edmund J. Mills, on purely. mathemat- 

 ical considerations, has calculated the boiling point of hydrogeu at —215° 

 C. This figure remains to be confirmed by Wroblewski and Olzewski, 

 who are separately engaged in investigating the subject. According to 

 the former, oxygen boils at —184° and nitrogen at —193*^, under the ordi- 

 nary pressure. Olzewski, who uses a hydrogen thermometer, claims to 

 have measured a temperature of —213° C. {Chem. News, l, 179.) 



Liquefaction of Oxygen by the Aid of Marsh Gas. — Cailletet has discov- 

 ered that marsh gas (formene) can be used to liquefy oxygen, without 

 employing mechanical means for lowering the temperature of boiling of 

 the cooling liquid. The formene is compressed and cooled in ethylene 

 boiling under atmosi>heric pressure; in the liquid state it is very mobile, 

 and in vaporizing lowers the temperature sufficiently to immediately 

 hquefy oxygen. This process greatly simplifies the liquefaction of oxy- 

 gen gas. {Comptes rendus, xcix, 15G5.) 



Atomic Weight of Carbon determined, by Combustion of the Diamond, by 

 C. Friedel. — Having obtained, through the generosity of Mr. Chatrian, 

 a number of very fine white diamonds from Africa, the author made 

 combustions in a current of oxygen, with a view to determining the 

 atomic weight of carbon with unusual accuracy. The experiments gave 

 C = 12.007 when = 1G. The ashes remaining after the combustion were 

 small white flakes, yellowish in places, with small black spots. Some 

 were attracted by the magnet ; several were transparent, and of these 

 some were acted on by polarized light, having preserved their crystal- 

 line form. The weight of the ashes was about 0.058 per cent, of the 

 diamond. 



During the combustion the diamond did not change into coke, as has 

 been claimed by others, but was merely roughened on the surface, as if 

 attacked by an acid. {Bull. soc. chim., xli, 100.) 



The Atomic weight of Glucinnm, by L. F. Nilson and Otto Pettersson. — 

 A few years ago these authors concluded, from their experiments on the 

 specific heat of glucinum, that the atomic weight of this element is 13 65, 



