ap] 



Chemistry and Physics. 319 



tates the compound PbFCl. For 0-1 K of NaF'in 50 cc of solution 

 the author uses 200 cc of the lead chloride. The liquid is allowed 

 to stand over night, filtered with a Gooch crucible, washed with 

 a nearly saturated lead chloride solution, then 2 or 3 times with 

 water, and the precipitate is dried for 2 hours at 140-150°. The 

 author has determined the solubility of the precipitate in water 

 and several other solutions, including lead chloride solution. It 

 is very sparingly soluble in the latter, much more soluble in 

 water, and still more soluble in hydrochloric and acetic acids. 

 The errors in 17 determinations of NaF by the above method 

 were from +0-46 to -0'30 per cent. Less accurate results were 

 obtained by dissolving the precipitate and determining the chlo- 

 rine. — Zeltschr. anorgan Chem., lxx, 173. h. l. w. 



3. Uranium Hexafluoride. — The preparation of this compound, 

 UF fi , is of considerable interest in connection with the valency of 

 uranium, since no hexahalide of this element has been previously 

 prepared. Ruff and Heinzelmann have prepared it in three 

 ways : By the action of fluorine upon uranium pentachloride in 

 the absence of moisture, when it is obtained mixed with the teti - a- 

 fluoride from which it is easily separated by volatilization. By 

 the action of anhydrous hydrofluoric acid upon uranium penta- 

 chloride the same products as before are obtained, but in this 

 case the very volatile hexafluoride cannot be satisfactorily sepa- 

 rated from hydrofluoric acid. The third method consists in treat- 

 ing metallic uranium or the carbide with fluorine mixed with a 

 little chlorine, where the latter gas acts as a catalyzer and causes 

 the complete conversion into hexafluoride, while fluorine alone 

 produces practically pure tetrafluoride. 



Uranium hexafluoride forms pale yellowish crystals boiling at 

 56° C. and melting under a pressure of two atmospheres at 69-5°. 

 It forms the heaviest known gas with a specific gravity of about 

 12 compared with air. It fumes strongly in the air and is highly 

 reactive. — Zeitschr. anorg. Chem., lxxii, 63. H. L. w. 



4. Nitrification by Ultra-violet Rays. — Berthelot and Gaude- 

 chon show that a solution of ammonia after being exposed to 

 ultra-violet rays for a few hours in the presence of oxygen gives 

 all the reactions for nitrites, but no nitrates could be detected. 

 Nitrites were formed from ammonium carbonate, chloride and 

 sulphate under similar conditions, but much more slowly in the 

 two latter cases where the extent of hydrolysis is small. Nitrates 

 are changed to nitrites by the action of the rays. There are many 

 points of resemblance between the action of these rays and that 

 of certain microorganisms. — Comples Hendus, clii, 522. 



h. l. w. 



5. An Electric Furnace for Chemical Purposes. — Fischer and 

 Tiede have described a furnace in which substances may be 

 heated to a very high temperature, approaching 3000° C, in a 

 vacuum by making use of a tube of metallic tungsten heated by 

 a powerful electric current. They were able by means of this 

 apparatus to distil considerable quantities of metallic tin in a 



Am. Jour. Sci.— Fourth Series, Vol. XXXII, No. 190.— October, 1911. 

 24 



