656 SCIENTIFIC RECORD FOR 1885. 



3. Calcium hydroxy -by drosulphide, CaSH,OH, absorbs carbon disul- 

 pbide, with formation of unstable basic calcium thiocarbonates, deciom- 

 posed slowly by hydrogen sulphide and readily by carbonic anhydride. 

 (J. Chem.. Soc. Lond., July, 1885, p. 478.) 



Decomposition of Didymium ; Praseodymium and Neodymium. — Dr. C. 

 A. von Welsbach read a paper before the Vienua Academy of Sciences 

 on June 18, in which he describes an alleged decomposition of the 

 elementary substance known as didymium. This decomposition was 

 effected by means of the double ammonium or sodium nitrates in pres- 

 ence of lanthanum. In spite of the different behavior of the constitu- 

 ent bodies many hundred fractional crystallizations were necessary for 

 their separation. The two new elements in solution are distinguished 

 by intense absorption bands, and share between them the absorption 

 bands of the peculiar spectrum hitherto ascribed to didymium. The 

 colors of the compounds differ; the salts of that element which ap- 

 proaches nearest to lanthanum are of a leek green; the salts of the 

 other element are rose or amethyst red. The latter body forms the 

 bulk of didymium. 



Both colors are almost complementary, but the amethyst red is by 

 far the more intense, so that a small quantity of the salts of this ele- 

 ment causes the green color of the others to disappear. The atomic 

 weights of the two new elements are according to preliminary deter- 

 minations very different, and vary considerably from the value hereto- 

 fore ascribed to didymium. For the first element the author proposes 

 the name praseodymium (Pr), and for the second neodymium (Ne). The 

 two elements, so far as has been observed, yield each only one series of 

 salts derived from the sesquioxide. Praseodymium peroxide evolves 

 chlorine on treatment with hydrochloric acid. {Ghemil-er Ztg, and Chem. 

 ¥€ws, Lii, 49.) 



Researches on the Complex Inorganic Acids (by Dr. Wolcott Gibbs). — 

 Another and weighty instalment of his laborious researches was pre- 

 sented by Dr. Gibbs to the American Academy of Arts and Sciences 

 early in June. Among other things, he shows that vanadic pentoxide 

 unites with phosphoric or arsenic pentoxides in various proportions to 

 form well-defined complex acids. Compounds of vanadic pentoxide, 

 vanadic dioxide, and phosphoric or arsenic pentoxide may be formed 

 possessing properties analogous to the corresponding compounds of 

 tungsten and molybdenum. Compounds exist which contain pyro- 

 phosphoric and metaphosphoric acids in the place of orthophosphoric 

 acid. Complex acids exist which contain two different modifications of 

 phosphoric acid, as, for instance, metaphosphoric and orthophosphoric 

 -acids or oxides. The salts of a majority of these complex acids crys- 

 tallize in well-defined forms. In a summary Dr. Gibbs catalogues the 

 formula of not fewer than 72 new salts discovered and analyzed in the 

 course of his prolonged investigations. {Proceedings Am. Acad. Arts 

 and Sciences, xix, 50.) 



