SCIENTIFIC INTELLIGENCE. 



L Chemistry and Physics. 

 1. On the Dldymium absorption-spectrum and the Atoi 

 weight of Cerium. — BUheig has examined the methods for 

 preparation of pure cerium and has made an elaborate determ 

 tion of its atomic weight. As the absorption spectrum of didym- 

 ium is so characteristic, the author made a careful study of it, 

 with a view to use it to prove the freedom of the cerium from this 

 metal. The pure sulphate in a tube 22 cm. long (1-0454 grams in 

 -50 c. c. of water) gave 11 bands. Upon dilution, it was found 

 that in this tube ^yVr g^^"^ ^^ ^^^ sulphate in 100 c.c. water— cor- 

 responding to iy^2 gram Di, — could be detected by its bands. 

 In a tube 52 cm. long, jtItt^^ gram of sulphate, corresponding to 

 5¥iT5 gram of didymiura, could be tfms detected. Using a 

 Duboscq, in place of the Hoffmann spectroscope, three additional 

 absorption lines were observed, making in all 14. The spectrum 

 given by a crystal of sulphate 0*9 mm. thick, contained 22 lines, 

 and was considerably different from the others. Plates of these 

 spectra are given. The cerium was obtained pure from the mixed 

 oxalates of the cerite earths, by igniting these without the addition 

 of magnesia, by solution in nitric acid, and precipitation of the 

 cerium as ceroso-ceric sulphate. This precipitate, after washing, 

 was obtained free from didymium by Gibbs' method. The atomic 

 weight of cerium was determined from the combustion of the 

 oxalate and was found to be, as a mean of ten closely concordant 

 results, to be 94-1782. The author adds some analytical data 

 concerning the salts of cerium, — J. pr. Gh.^ II, xii, 209, Nov., 

 1875. G. F. B. 



2. On the Density of Platinum, of Iridium and of their Alloys. 

 — Sainte-Claire Deville and Debray have prepared with great 

 care both platinum and iridium in a state of purity and have 

 determined the density of these metals as well as that of several 

 of their alloys. The methods which they made use of to purify 

 these metals are given at length in their memoir. The platinum 

 ingots weighed from 200 to 250 grams, and gave a density of 

 21-5. The iridium, after breaking under the rolls, had a density 

 of 22-42104; in the ingot, as melted, of 22-239. An alloy of 90 

 per cent of platinum and 10 of iridium had a density of 21 -615 ; of 

 platinum 85 and iridium 15, of 21-618; of 66-67 platinum and 

 33-33 iridium, 21-874; of platinum 5 and iridium 95, 22-384; thus 

 increasing quite regularly.— (7. B., Ixxxi, 829, Nov., 1875. 



3. New method of Chlorinating Hydrocarbons.- 



