D. CHEMISTRY AND METALLURGY. 201 



soda very rich in soluble salts and alkaline iodides. While 

 the incineration gives but fifteen per cent, of potash and one 

 per cent, of iodide, the new process yields forty to fifty per 

 cent, of potash, and sometimes six per cent, of iodide. The 

 residual weeds are applicable to agricultural purposes. 1 A, 

 Juhj 21, 1876, 32. 



ATOMIC WEIGHT OF CERIUM. 



BUhrig, by means of a series of careful combustions of 

 cerium oxalate, has very accurately redetermined the atomic 

 weight of the metal. This, based upon the values given by 

 Stas for carbon and oxygen, he finds to be 94.1782. This 

 value is the mean of results obtained in fifteen exjDeriments. 

 Journal fur prakt. Chemie, XII., 209. 



THE CEKIUM METALS. 



The rare metals cerium, lanthanum, and didymium have 

 at last had their atomic weights definitely fixed by Hille- 

 brand. He determined the specific heat of each metal by 

 means of Bunsen's ice calorimeter, getting the following 

 values : Cerium, 0.04479 ; lanthanum, 0.04485 ; didymium, 

 0.04563. These figures, considered with reference to Dulong 

 and Petit's law, correspond respectively to the atomic weights 

 138, 139, and 144.78. These observations prove that the 

 lower oxides of these metals are really sesquioxides, and the 

 higher oxides, dioxides. Until lately the atomic weights of 

 this group have been rated at only two thirds of the above 

 values. Poggendorff''s A7i7icden, 1876, No. 5. 



CEKIUM, LANTHANUM, AND DIDYMIUM. 



These rare metals have recently been isolated in quantity 

 by Drs. Hillebrand and Norton, students under Bunsen at 

 Heidelberg. Cerium outwardly resembles iron, is very duc- 

 tile and malleable, and tarnishes readily. In hardness it 

 about equals silver, and its melting-point is at a full red heat. 

 Heated in the air it kindles very easily, at a lower tempera- 

 ture even than magnesium, burning with great brilliancy. 

 Upon shaving a cerium wire with a knife the thin fragments 

 of metcTl ignite as they are cast oft', while with an ordinary 

 fire-steel sparks can be struck from it as from a flint. Didy- 

 mium and lanthanum resemble cerium closely, but are less 



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