514 Scientific Intelligence. 



dioxide has formed a layer of from half a centimeter to a centi- 

 meter in thickness. The author is continuing his investigations 

 upon these phenomena. — Ber. Berl. Chem. Ges., xxiv, 1031, 

 April, 1891. g. f. b. 



4. On the Molecular Formula of Hydrogen Fluoride. — Pa- 

 teexo and Peeatoxer have determined the molecular mass of 

 hydrogen fluoride by means of the lowering of the freezing point 

 which it produces, the apparatus being the one ordinarily em- 

 ployed for this purpose, except that it was made entirely of 

 platinum. The thermometric vessel was contained in a platinum 

 tube, closed at its lower end and extending nearly to the bottom 

 of the apparatus, being fastened to the cover. The space 

 between the thermometric vessel and the walls of the tube was 

 filled with mercury. After a series of comparative experiments 

 proving this apparatus to give results coinciding with those 

 obtained with a glass apparatus, it was applied to the determina- 

 tion of the molecular mass of hydrogen chloride in aqueous solu- 

 tions of various strengths ; and the results led uniformly to the 

 formula HC1. On repeating the experiments with hydrogen 

 fluoride however, the molecular mass obtained corresponded 

 always to the doubled formula H 2 F 2 . Whether for more dilute 

 solutions still this double molecule will split into two simple 

 ones, farther experiments must determine. This result confirms 

 the conclusion reached by Mallet by the vapor density method. — 

 Ber. Berl. Chem. Ges., xxiv, (Ref.)"298, April, 1891. g. f. b. 



5. On the Extraction of Oxygen from the Air. — Kassner has 

 recently given further particulars concerning his process for ex- 

 tracting oxygen from the air on a commercial scale, based on the 

 successive formation and decomposition of calcium plumbate. 

 He now finds that in producing this plumbate, it is better to use 

 a slight excess of calcium carbonate, say five per cent. Two 

 niolugrams (a molugram is the molecular mass in grams) of 

 calcium carbonate, with this excess, is heated with one of lead 

 oxide ; and a resulting spongy product is obtained in this way, 

 in which nearly the whole of the lead oxide is converted into the 

 plumbate. The calcium carbonate is used in the form of lime- 

 stone and it has been found unnecessary to stir the materials 

 during the heating, which may be effected in an ordinary reverb- 

 eratory furnace well supplied with air. To recover the oxygen 

 the author heats the calcium plumbate in the presence of carbon 

 dioxide, when the following reaction takes place: 



Ca 2 Pb0 4 + (CO s ,) 2 =(CaC0 3 ) 2 + PbO + O. 

 So that the process is a continuous one, the quantity of oxygen 

 obtainable from a given quantity of charge being unlimited. 

 Since the formation of the plumbate requires only a few minutes, 

 and since its decomposition by the carbon dioxide is complete, 

 the author thinks this process preferable to those of Boussingault 

 and Brin ; especially since the value of the material, the cost of 

 the plant and the working expenses are extremely small. — Dingl. 

 J., cclxxviii, 468; J. Chem. <Soc, lx, 392, April, 1891. G. f. b. 



