PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 459 



passed through the solution to precipitate all of the copper, lead, 

 arseuic, tin, cadmium and molybdenum; oxydize the tiltrate from 

 the above, and then add a large excess of ammonia, by which the 

 greater portion of the zinc will be dissolved and separated; dis- 

 solve the precipitate produced by the ammonia in acetic acid, and 

 throw down the indium as a sulphide by means of sulphuretted 

 hydrogen. In order to obtain a pure salt, this latter operation 

 will require to be repeated a number of times. 



The metal is more easily obtained from a granulated zinc than 

 from blende. 



Schrotter has found indium in the blende of Schonfeld, near 

 Schlaggenwald. He roasts the finely stamped ore and digests it 

 in sulphuric acid, and throws down the indium by metallic zinc, 

 in the same manner that thallium is precipitated from its solu- 

 tions. Schrotter has also determined the exact position of the 

 indium lines with reference to Kirchhoff's chart of the solar spec- 

 trum and the photograph of the spectrum taken by Mr, Ruther- 

 furd, of New York. 



Mr. Rutherfurd's photograph is now accepted as the standard 

 of measurement by the physicists of Europe, and is regarded as 

 one of the most valuable contributions to science ever received 

 from this country. 



Streng has found indium in the furnace products of the Hartz 

 mountuins. 



Professor Joy has examined fifteen specimens of blende, from 

 as many localities, in widely separated portions of the United 

 States, but thus far no trace of indium has been discovered. 



The effect of indium upon the fusibility of alloys, has not been 

 determined, but reasoning from analogy, it appears probable that 

 it would lower the point of fusion, the same as cadmium. 



There is every reason to expect that the indiftm blende will be 

 discove«'ed just as a cadmium blende was found on the estate of 

 Lord Greenock, in Scotland. What influence the bromide and 

 iodide of indium would have in photography, also remains a 

 question for investigation. 



Indium is emphatically a metal of the future. 



Rubidium. 

 This metal was discovered by Bunsen and Kirchhofl' in 1861. 

 Bun.^en is a native of Goettingen, and is a cousin of the late Cheva- 

 lier Bunsen, so well known for his theological writings. 



