Chemistry and Physics. 429 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Physical Properties of Fluorine. — Having estab- 

 lished the fact that when fluorine is free from hydrogen fluoride, 

 it does not attack platinum at temperatures below 100°, Moissan 

 has made use of containing vessels of this metal in order to 

 determine the physical constants of free fluorine. By means of a 

 platinum bottle of about 100 c. c. capacity, provided with a 

 platinum tube passing through the stopper and having a lateral 

 tube attached to the neck which could be closed by i*otating the 

 stopper, the density was determined. For this purpose the bottle 

 after weighing was filled with dry nitrogen, and then with fluorine 

 by displacement, the current being continued until the issuing 

 gas readily ignited silicon. After a second weighing, the bottle 

 was inverted in water, the oxygen set free by the fluorine was 

 absorbed by alkaline pyrogallate solution, and the residual nitro- 

 gen measured. From the volume of the fluorine thus obtained, 

 knowing the increase in the mass of the bottle, the density of the 

 fluorine was easily found. Four determinations thus made gave 

 values varying from 1*264 to 1*270 as compared with air; the 

 value 1*265 being adopted by the author. Calling the atomic 

 mass of fluorine 19*05, the theoretical density is 1*314. The color 

 of fluorine was examined in a platinum tube a meter long and of 

 about 200 c. c. capacity, having two lateral tubulures for the in- 

 troduction of the gas, and closed at the ends with colorless plates 

 of fluorite. Viewed against a white surface, the gas possessed 

 a very distinct greenish-yellow color, weaker and more yellow 

 than that of chlorine under the same conditions. No absorption 

 bands were observed. The emission spectrum of fluorine was 

 obtained by placing the gas in a platinum tube furnished with a 

 lateral tube closed with a plate of fluorite, the electrodes at the 

 ends of the main tube being insulated by the fluorite plates 

 which closed these ends. Using an induction coil giving a 10 cm 

 spark in air and placing a condenser in the secondary circuit, the 

 spark in the fluorine was examined with a spectroscope having 

 three heavy glass prisms. Both platinum and gold electrodes 

 were used. With the former, thirteen lines of fluorine were 

 observed, of wave-lengths 744, 740, 734, 714, 704, 691, 687*5, 

 685*5, 683*5, 677, 640*5, 634 and 623. The first three of these 

 are very weak, the last four are strong. Of these only four, of 

 wave-lengths 704, 640, 634 and 623 appear in hydrogen fluoride 

 under the same conditions; while in silicon fluoride, ten of these 

 lines, in phosphorus fluoride seven, in phosphoric fluoride six 

 and in carbon tetra-fluoride the entire thirteen are visible. No 

 trace of liquefaction was observed when fluorine was subjected to 

 a temperature of —95° in a bath of solid carbon dioxide and 



