Hoppe-Seyler on the occurrence of Indium. 33 



hesion of its particles, almost entirely dependent on the compo- 

 sition of adjacent layers of liquid. An action at a distance or 

 an action of mass could be observed here just as little as in che- 

 mical processes. 



(2) Owing to the quick decrease of the velocity of this motion, 

 an equalization in the composition of two diffusible layers of 

 liquid, lying one upon the other, is only attained in several 

 months or even years, if the height of each of these layers amounts 

 from 1 to 1^ decimetre. According to the author's experiments, 

 this cannot be doubted in the case of sugar ; the diffusion of salts 

 in liquids is probably more rapid. 



(3) The penetration of particles of sugar in its diffusion 

 through water is not appreciably hindered by the concentration 

 of the solution already formed. The author considers it pro- 

 bable that in concentrated layers viscosity hinders diffusion ; on 

 the other hand, the attraction of particles of sugar for particles 

 of water is always less, the greater the quantity of water that 

 already surrounds the former, so that these opposing actions pro- 

 duce an equalization of the velocity of diffusion in concentrated 

 and dilute solutions. 



(4) Cane-sugar and grape-sugar exhibit under similar circum- 

 stances almost equal diffusive velocity in water. Serous albumen 

 and gum diffuse in water with extreme slowness. 



Hoppe-Seyler has found indium* both in Wolfram of un- 

 known origin, and in a specimen from Zinnwald. From a pre- 

 liminary determination he found in the former 00228 per cent, 

 oxide of indium. The Wolfram contained some zinc, but no 

 sulphur, and therefore contained no blende. For its prepara- 

 tion, the mineral may either be digested with hydrochloric and 

 nitric acids, or be fused with carbonate of soda, experiments 

 having shown that in this way there is no appreciable loss of in- 

 dium. The indium is separated from the other metals contained 

 in Wolfram by the usual methods. 



Richterf, the discoverer of indium, gives the following method 

 of obtaining the metal : — The residue left after dissolving zinc in 

 sulphuric acid contains indium and various other metals. This 

 is dissolved in nitric acid, and the solution, mixed with sulphuric 

 acid, is evaporated ; into this solution, which must be largely 

 diluted and but slightly acid, sulphuretted hydrogen is passed, 

 which precipitates the indium along with cadmium and copper. 



This precipitate is dissolved in hydrochloric acid, precipitated 

 by ammonia, and this treatment repeated until all cadmium and 

 zinc are separated from indium. The last quantities of iron 

 which remain mixed with indium are removed by a partial pre- 

 cipitation by ammonia and carbonate of soda. 



* Liebig's Anncden, vol. cxl. p. 247. 

 ' f Comptes Rendus, April 22, 1867. 



Phil. Mac/. S. 4. Vol. 34. No. 227. July 1867. D 



