Chemistry and Physics. 477 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Solid Fluorine and its Combination with Liquid Hydro- 

 gen. — Moissan and Dewae have shown, some time since, that 

 fluorine liquefies at —187°, and that, at this low temperature, it 

 does not act upon crystalline silicon, amorphous carbon, boron or 

 mercury, but that it does combine violently with gaseous hydro- 

 gen and solid essence of turpentine. These investigators have 

 recently subjected fluorine to the temperature of boiling hydro- 

 gen ( — 252*5°). As this cooling takes place the fluorine gas 

 liquefies, then forms a yellow solid, and finally the solid becomes 

 white. It was found that the melting-point of solid fluorine is 

 about 2° higher than that of solid oxygen, or about —233°. 



The interesting fact was observed that solid fluorine when 

 brought in contact with liquid hydrogen at the temperature of 

 the latter, —252*5°, produces a violent explosion. It appears, 

 therefore, that chemical energy exists at this low temperature, 

 which is only 20° above the absolute zero. 



The solidification of fluorine leaves only one known gas, 

 helium, which thus far has not been brought into the solid con- 

 dition. — Comptes Rendus, cxxxvi, 641. h. l. w. 



2. Hydrides of Rubidium and Caesium. — Moissan has pre- 

 pared the hydrides of the rare alkali-metals rubidium and caesium, 

 and finds that they correspond exactly to potassium hydride. 

 They correspond to the formulas RbH and CsH, and form color- 

 less crystals. Both compounds are decomposed by heating in a 

 vacuum below 300° into hydrogen and metal. They take fire at 

 ordinary temperatures in air, oxygen, chlorine, fluorine and 

 bromine vapor. Heated in nitrogen gas they form mixtures of 

 nitride and amide. They are decomposed rapidly by water at 

 ordinary temperatures, but without incandescence, forming the 

 metallic hydroxides and hydrogen. When acted upon by sulphur 

 dioxide at low temperatures and diminished pressure they form 

 the hydrosulphites Rb 2 S 2 4 and Cs 2 S 2 4 . At a gentle heat car- 

 bon dioxide combines with them to form the formates. They 

 react with ammonia gas and form the amides. — Comptes JRendus, 

 cxxxvi, 587. h. l. w.' 



3. Combustion in Gaseous Mixtures other than Air. — Very 

 conflicting statements have been made in regard to the amount 

 of carbon dioxide which, when it is mixed with air, will extin- 

 guish a flame ; for example, Eulenberg asserts that extinction 

 occurs at 3 per cent of C0 2 , Taylor at 10 per cent, Graham-Otto 

 at 20 per cent, and Arnould at 25 per cent. Pelet and Jomini 

 have recently made numerous experiments by using candle, alco- 

 hol, and illuminating-gas flames in mixtures of nitrogen and oxy- 

 gen, carbon dioxide and oxygen, and also in mixtures of the three 

 gases. After the flames had been extinguished the resulting mix- 



