512 



METALS. 



in cacao-beans and chocolate. M. G-. Duclaux 

 lias quantitatively tested some nineteen sam- 

 ples in all of cacao-beans (Theobroma, cacao), 

 for tbe quantity of ash and copper therein con- 

 tained, observing that, unless the incineration 

 is very complete, the copper is retained tena- 

 ciously by the carbonaceous matter. As re- 

 gards the quantity of copper in 1,000 parts of 

 ash, it varies, for cacao-beans, from 0.009 to 

 0.040 ; for the outer shell (husks) of the same, 

 for 1,000 parts, from 0.035 to 0.225; for choco- 

 late of various makers, for 1,000 parts, from 

 0.005 to 0.125. The copper is first precipitated 

 from its acid solution by sulphuretted hydro- 

 gen, and this sulphuret, having been redissolved 

 in a platinum crucible, is next reduced to the 

 metallic state by means of zinc put into contact 

 with the platinum. The author further states, 

 at great length, that the platinum crucible 

 employed in this operation becomes to some 

 extent converted into an alloy of platinum and 

 hydrogenium, whereby its weight is altered, 

 and that, in order to counterbalance this effect, 

 it is best to wash, after precipitation of the 

 copper, the crucible with alcohol, next dry it 

 at 100. then ignite it strongly, and lastly, 

 weigh it with the copper, which is then re- 

 moved by some nitric acid. 



Indium. A full history of this new and rare 

 metal has been given by Prof. William Odling, 

 in a paper read before the Eoyal Society. It 

 was first recognized in 1863, by Drs. Eeich 

 and Eichter, in the zinc-blende of Freiberg, 

 through the agency of the spectroscope, by 

 which instrument Dr. William Orooke detected 

 thallium in 1861. The spectrum of indium 

 consists of two bright indigo bands, the bright- 

 est somewhat more refrangible than the blue 

 line of strontium, and the other somewhat less 

 refrangible than the indigo line of potassium. 

 Indium has since been found in one or two 

 varieties of wolfram; but its chief source is 

 metallic zinc that of Freiberg, smelted from 

 the ore, containing very nearly one-half part 

 of indium to 1,000 parts of zinc. It has been 

 obtained in ingots of over seven ounces. Prof. 

 Odling says : 



When zinc containing indium is dissolved not quite 

 completely in dilute sulphuric or muriatic acid, the 

 whole of the indium originally present in the zinc is 

 left in the black, spongy, or flocculent residue of un- 

 dissolved metal, with "which every one, who has pre- 

 pared hydrogen gas by means of zinc and acid, is so 

 well acquainted. Besides some zinc, this black resi- 

 due is found to contain lead, cadmium, iron, and 

 arsenic, less frequently, copper and thallium, and in 

 some cases, as that of the Freiberg zinc, a small pro- 

 portion of indium. _ From the solution of this residue 

 in nitric acid, the indium is separated by ordinary 

 analytical processes, based chiefly on the precipita- 

 bility of its sulphide by sulphuretted hydrogen from 

 solutions acidulated only with acetic acid; and on 

 the prceipitability of its hydrate both by ammonia 

 and carbonate of barium. From its soluble salts, 

 metallic indium is readily thrown down in the spongy 

 state by means of zinc. The washed sponge of metal 

 is then pressed together between filtering-paper, by 

 aid of a screw press, and finally melted under a flux 

 of cyanide of potassium. 



Thus obtained, indium is a metal of an almost sil- 



ver-white color, apt to become faintly bismuth-tinted. 

 It tarnishes slowly on exposure to air, and thereby 

 acquires very much the appearance of ordinary lead. 

 Like lead, it is compact and seemingly devoid of 

 crystalline structure. Moreover, like lead and thal- 

 lium, it is exceedingly soft, and readily capable of 

 furnishing wire, by the process of "squirting" or 

 forcing. The. specific gravity of indium, or 7.4, is 

 very close to that of tin, or 7.2 ; and much above 

 that of aluminum, 2.6, and below that of lead, 11.4, 

 and that of thallium, 11.9. In the lowness of its 

 melting-point, viz., 176 C., indium occupies an ex- 

 treme position among the metals permanent in air 

 the next most fusible of these metals, viz., tin and 

 cadmium, melting at 228, bismuth at 264, thallium 

 at 294, and lead at 235. Though so readily fusible, 

 indium is not an especially volatile metal. *It is ap- 

 preciably less volatile than the zinc in which it occurs, 

 and far less volatile than cadmium. Heated as far 

 as practicable in a glass tube, it is incapable of being 

 raised to a temperature sufficiently high to allow of 

 its being vaporized, even in a current of hydrogen. 



Indium resists oxidation up to a temperature some- 

 what beyond its melting-point, but at much higher 

 temperature it oxidizes freely ; and at a red heat it 

 takes fire in the air, burning with a characteristic 

 blue flame and abundant brownish smoke. It is 

 readily attacked by nitric acid, and by strong sul- 

 phuric and muriatic acids. In diluted sulphuric and 

 muriatic acids, however, it dissolves but slowly, with 

 evolution of hydrogen. Oxide of indium is a pale- 

 yellow powder, becoming darker when heated, and 

 dissolving in acids with evolution of heat. The hy- 

 drated oxide is thrown down from indium solutions 

 by ammonia as a white, gelatinous, alumina-like 

 precipitate, drying up into a horny mass. The sul- 

 phide is thrown down by sulphuretted hydrogen as 

 an orange-yellow precipitate, insoluble in acetic, but 

 soluble in mineral acids. The hydrate and sulphide 

 of indium, in their relations to fixed alkali solutions 

 more particularly, seem to manifest a feebly-marked 

 acidulous character. Chloride of indium, obtained 

 by combustion of the metal in chlorine gas, occurs 

 as a white micaceous sublimate, and is volatile at a 

 red heat without previous fusion. The chloride 

 itself undergoes decomposition when heated in free 

 air^ and the solution of the chloride upon brisk evapo- 

 ration, with formation in both cases of an oxychlo- 

 ride. 



Treatment of Tinned Scraps. Dr. Adolph 

 Ott, of New York, has recently applied the 

 Seely process for separating the tin from tin 

 scraps, and thus utilizing a waste product. 

 Chlorine gas is turned upon a pile of the scrap- 

 tin in a proper apparatus, and the metal is dis- 

 solved off in the form of bichloride. Dr. Ott 

 describes some of the steps of the process and 

 the general results as follows: 



The iron obtained by the action of chlorine upon 

 tin scraps is by no means perfectly free from tin, 

 even if every surface has been exposed to the action 

 of the gas. Dr. H. Endemann, assistant-chemist to 

 the Department of Health of New York, found in 

 such scraps, treated by me, 0.096 per cent, of tin, and 

 I never failed to detect traces of tin on scraps treated 

 in the manner described. While such a small per- 

 centage cannot possibly have any injurious effect, 

 especially if the scrap-iron is worked up with other 

 iron, it is rather doubtful, when the clippings are not 

 loosely heaped up, whether the resulting iron will 

 be sufficiently pure for the puddling-furnace. The 

 success of the process depends, indeed, principally 

 upon the careful execution of the " charging." Flat 

 pieces ought to be mixed with bent pieces and strips 

 in such a manner that there will finally be as few 

 pieces as possible covering each other. 



Regarding the space which one ton of clippings 

 of 2,000 IbsT occupies, I found it to be on the average 



