Chemistry and Physics. 493 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Separation of Titanium, Niobium and Tantcdum. — 

 The quantitative separation of these three acid-forming elements 

 has been regarded as one of the most difficult problems of analy- 

 tical chemistry. Ltjdwig Weiss and Max Landecker of the 

 University of Munich have, now made an elaborate study of the 

 matter, and they appear to have made a great advance in the 

 solution of this problem by the use of unexpectedly simple opera- 

 tions. An outline of their method for the analysis of columbite 

 and tantalite is as follows: The usual fusion is made with acid 

 potassium sulphate, the resulting mass, after cooling, is extracted 

 with hot water containing sulphuric acid, and to the boiling solu- 

 tion sulphurous acid is added in moderate amount (20 or 30 cc ) 

 until the precipitate loses its milky appearance and becomes 

 flocculent. After boiling for 20 or 30 minutes the precipitate, 

 which contains the tin and the rare acids, is filtered and washed 

 with a hot solution of sulphuric and sulphurous acids. It is 

 advisable to pass hydrogen sulphide through the nitrate and to 

 collect any tin that may have remained in solution. This filtrate 

 is then to be analyzed for the metals by the usual methods. The 

 precipitate of acids is now treated thoroughly, as usual, with hot, 

 yellow ammonium sulphide for the extraction of tin. The residue 

 is ignited and fused in a platinum crucible with sodium carbonate 

 and with the addition, shortly before the end of the fusion over 

 the blast lamp, of a little sodium nitrate in such a way (igniting 

 only for 8 or 10 seconds) that some of the latter remains unde- 

 composed. The amount of sodium carbonate should be only about 

 double that of the mixed acids, and the sodium nitrate should be 

 used sparingly. The mass is then extracted with boiling water 

 for some time in order to dissolve all the tantalate, the insoluble 

 titanium residue is filtered off, and a few drops of the filtrate are 

 tested with hydrogen peroxide for titanium. If this is present, as 

 is the case only when more than from 3 to 5 per cent of titanium 

 is present, hydrogen sulphide gas is passed into the cold liquid, 

 producing a grayish-white precipitate containing all the titanic 

 acid present here, and thus separating it from niobium and 

 tantalum. This precipitate is washed with sodium sulphide. If 

 titanium is not present, carbon dioxide is led into the liquid in 

 order to precipitate tantalum and separate it from niobium, 

 but when hydrogen sulphide has been used it is necessary to 

 destroy the sodium sulphide with sulphuric acid, to precipitate 

 the acids with ammonia, and to make another fusion with sodium 

 carbonate and nitrate in order to obtain a solution suitable for 

 the precipitation of tantalic acid. This operation is performed 

 by passing the carbon dioxide for a long time in the cold. The 



Am. Jour. Sci.— Fourth Series, Vol. XXVIII, No. 167.— November, 1909. 

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