374 Scientific Intelligence. 



down with the tellurium to some extent. They find this to be 

 the ease particularly with copper. As a means of separating tel- 

 lurium from some of these metals they convert the tellurium into 

 telluric acid and then precipitate the other metals as sulphides, 

 leaving the telluric acid in solution, since hydrogen sulphide 

 does not act upon this compound at all until after a long time. 

 Their method in detail is as follows: The tellurium contaminated 

 with a heavy metal (Cu, Bi, Sb) is collected on a Gooch filter, dis- 

 solved in nitric acid, the solution is evaporated, the residue is 

 dissolved in potassium hydroxide (1 : 5), and in a well covered 

 vessel (Erlenmeyer flask) is oxidized by the gradual addition of 

 ammonium persulphate (about 4 — 6 s ). After the excess of the 

 latter has been removed by boiling, the liquid is acidified with 

 sulphuric acid, and to the cold liquid 100 cc of hydrogen sulphide 

 water are added. The excess of hydrogen sulphide is then 

 removed by means of a rapid stream of carbon dioxide. The 

 sulphide is then filtered off and brought into a weighable form 

 by an appropriate method. The telluric acid may be reduced to 

 tellurous acid by adding hydrochloric acid and boiling down to 

 25 cc , as has been shown by Gooch and his co-workers, and then 

 the tellurium may be precipitated by means of sulphur dioxide 

 water. The authors collect this precipitate on a Gooch filter and 

 dry it at 120° in a stream of carbon dioxide. — Berichte, xl, 3362. 



h. l. w. 

 3. The Rays from Thorium Products. — The assumption by 

 Hahn" of the existence of a product, mesothorium, intermediate 

 between thorium and radiothorium, was noticed in the July num- 

 ber of this Journal. Hahn now considers the existence of meso- 

 thorium as fully established by further experiments. He has 

 found also that mesothorium, at first considered to be rayless, 

 gives off /J-rays, and he reaches the conclusion, in an indirect 

 manner, that thorium itself gives off a-rays of a peculiar kind. 

 He gives the following list of the radio-active thorium products 

 and the kind of rays given off by each : 



Thorium a-rays. 



Mesothorium /3- " 



Radiothorium a- " 



Thorium X a- " 



Emanation a- " 



Thorium A slowly /3-rays. 



Thorium B ) n , 



Thorium C " a > P+-T™?* 



rs 



— Berichte, xl, 3304. h. l. w. 



4. The Decomposition of Gaseous Hydrocarbons by Ignition 

 with Powdered Aluminium. — Kusnetzow has found that the 

 hydrocarbons, methane, ethane, ethylene and acetylene, are com- 

 pletely decomposed when they are passed several times through 

 a tube containing aluminium powder and heated to the melting 



