150 Scientific Intelligence. 



capacity of 160 cc . It was immersed during electrolysis in boiling 

 methyl chloride, giving a temperature of — 23°. In this tube a 

 mixture of 100 cc hydrofluoric acid and 20 grams HKF 2 was con- 

 tained ; and this under the action' of 26 to 28 Bunsen cells ar- 

 ranged in series, evolved four liters of pure fluorine per hour. 

 The gas as evolved was first conducted through a platinum spiral 

 placed in a bath of boiling methyl chloride and maintained at 

 about — 50°, for the purpose of condensing the accompanying 

 hydrogen fluoride, which boils at 19-5°. It was then passed 

 through platinum tubes filled with fragments of fused sodium 

 fluoride, by which the last traces of the hydrogen fluoride were 

 removed. At the beginning of the electrolysis the fluorine 

 attacks the positive electrode, which is of pure platinum, produc- 

 ing PtF 4 . This apparently unites with the potassium fluoride to 

 form (KF) 2 PtF 4 ; and it is only when the liquid contains this 

 double salt that the electrolysis proceeds regularly. Pure fluorine 

 possesses an odor resembling that of a mixture of hypochlorous 

 acid and nitrogen peroxide; though this odor is masked by that 

 of the ozone formed by its action upon moist air. In a thickness 

 of one meter it has a greenish yellow color, paler and more yellow 

 than that of chlorine ; but its spectrum shows no absorption bands. 

 Its spark spectrum shows 13 bright lines in the red between 

 X = 0*744^ and 0-623'". Its density, as the result of many exper- 

 iments, appears to be 1-265, the theoretical value being 1'316. 

 It is not liquefied at — 95° at the ordinary atmospheric pressure. 

 Fluorine combines with hydrogen with explosion, even in the 

 dark and at a temperature of — 23°. With oxygen, on the other 

 hand, it does not unite even at 500°. When fluorine acts on 

 water a peculiar odor is noticed, which soon passes into that of 

 ozone and which the author thinks may be due to an oxide of 

 fluorine. Many other reactions are given in Moissan's paper. — - 

 Ann. Chem. P%s., VI, xxiv, 224, Oct., 1891; Nature, xliv, 622, 

 Oct., 1891. G. r. B. 



3. On the commercial production of Ozone. — In a recent lecture 

 by Feolich he has given an account of the experiments which 

 have been made in the laboratory of Siemens and Halske in Ber- 

 lin for the commercial production of ozone. The original Siemens 

 ozonizing tube consisted of two concentric glass cylinders, the 

 inner one coated interiorly and the outer one exteriorly with 

 metal ; these two coatings being supplied with an alternating 

 current of high potential, while oxygen was made to traverse the 

 annular space between them. It now appears that only one 

 dielectric is necessary, mica, celluloid, porcelain and the like 

 being available as well as glass, and the ozone-tube having either 

 a metal tube within and a metal-coated non-conducting tube with- 

 out, or a metal tube without while the inner tube is made of the 

 non-conducting material and lined with metal. The metals to be 

 used are of course those which are not attacked by ozone, such as 

 platinum, tin or aluminum. Cold water flows through the inner 

 tube, and through the annular space pure dry air. Several such 



