1867.] Chemistry. 97 



With regard to Indium, Winckler * has published a process for 

 its easy extraction from Blende. He treats the roasted blende with 

 hydrocliloric acid, then by an excess of zinc precipitates the indium 

 together with copper, lead, cadmium, &c, and afterwards separates 

 these metals by means of sulphuretted hydrogen and carbonate ot 

 baryta. 



In connection with zinc we may mention the publication by 

 B. Eenault t of some notes on the phosphor etted compounds of this 

 metal. He finds that zinc and phosphorus unite in many and 

 variable proportions, and he describes no fewer than six phosphides, 

 only one of which calls for notice. This is the compound Zn 3 P, 

 which will keep without alteration even in the air, and serves well 

 for the preparation of spontaneously inflammable phosphoretted 

 hydrogen. The author prepares this compound by mixing one 

 equivalent of phosphate of magnesia, with two of artificial sulphide 

 of zinc, and seven of carbon. The mixture is heated in an earthen 

 crucible, and the phosphide of zinc sublimes. Hydrochloric acid 

 added to fragments of the phosphide, causes the evolution of gas 

 which inflames at 30°, but with the powder, the spontaneously 

 inflammable gas is obtained. 



Mr. Carey Lea has suggested an extremely delicate test for the 

 detection of iodine. To a solution, for example, suspected to contain 

 iodide of potassium, the author adds, 1st, a drop or two of solution 

 of starch, then a drop of a dilute solution of bichromate of potash, 

 just sufficient to give a pale yellow colour to the liquid, and lastly, 

 a few drops of dilute hydrochloric acid. The effect varies of course 

 with the amount of iodine present, but with a solution of iodide of 

 potassium, containing only Too.Vooth, an abundant blue precipitate 

 is obtained, which, however, becomes tawny as the dilution increases. 

 In the case of great dilution, approaching to a half-millionth, merely 

 a tawny shade is given to the solution. 



The same indefatigable experimenter has carried still further his 

 researches on the chemistry of the photographic picture. Contrary to 

 the assertion of Vogel, he shows that light has an action, on perfectly 

 neutral iodide of silver, since he has produced an image on silvered 

 glass, merely treated with solution of iodine. The physical part of 

 the paper we may leave unnoticed here, and merely give the author's 

 opinion that on an ordinary negative there are really four super- 

 imposed pictures : 1st, that produced by the physical action of light 

 on iodide of silver ; 2nd, another by the reduction of iodide to 

 subiodide of silver, if the exposure has been sufficiently long ; 3rd, 

 one produced by light in connection with the organic matter of the 

 film ; and 4th, the reduction of bromide and chloride if present. 

 With regard to the 3rd, it should be mentioned that the author 



* ' Journ. f. prakt. Chemie.' xciv., p. 114. 

 t ' Annales de Chimie tt de Pharm.,' Oct., i860. 

 VOL. IV. H 



