464 



METALS. 



was promoted to the rank of rear-admiral in 

 1866. 



METALS (see also CEEIUM, HYDEOGENIUM, 

 and THALLIUM). Rhodium. Professor E. Bun- 

 sen has conducted an elaborate series of ex- 

 periments on the separation of rhodium from 

 the platinum ores with which it is associated. 

 For the purposes of his investigations, the 

 Imperial Mint at St. Petersburg supplied him 

 with large quantities of the products obtained 

 in working platinum ores on the large scale. 

 These residues were : 1. Those which remain 

 after the application of aqua regia, and which 

 are specially rich iu osmium and iridium ; 2. 

 Osmium-indium, which is separated from the 

 first residues by lixiviation, and which serves 

 best for the preparation of ruthenium ; 3. The 

 residues of the mother liquors, which have 

 been reduced by iron from the aqua regia solu- 

 tion from which the platinum has been re- 

 moved. The latter residues, being rich in pal- 

 ladium and rhodium, are most conveniently 

 used as a source of those metals. Professor 

 Bunsen's labors having been directed principal- 

 ly to the redaction of rhodium, a detailed ac- 

 count of his separation of the other metals in 

 the residues may properly be omitted. By a 

 succession of ingenious processes he at last 

 obtained a solution in which only iridium and 

 rhodium were present. To separate these met- 

 als from each other, the liquid was evaporated 

 with hydrochloric acid, filtered, mixed with 

 a great excess of bisulphite of soda, and left 

 to stand in the cold for several days. Eho- 

 dium was slowly deposited as an amorphous 

 lemon-yellow soda double sulphite, while the 

 solution became yellow, and finally decolor- 

 ized. TVith this change of color, the rhodium 

 precipitate also became brighter. The pre- 

 cipitate, well washed out with water, contained 

 the rhodium almost entirely free from impu- 

 rities. The solution being warmed in the water- 

 bath in a loosely-stoppered flask, a fresh pre- 

 cipitate was formed, which was yellowish 

 white, and consisted mainly of the before-men- 

 tioned rhodium salt, mixed with a greater or 

 less quantity of the corresponding iridium salt. 

 The complete separation of iridium from rho- 

 dium was readily effected merely by treating 

 the yellow precipitates with concentrated sul- 

 phuric acid. The precipitate was added in 

 small portions to the sulphuric acid, heated in 

 a platinum crucible until sulphuric acid was 

 disengaged, and the crucible heated in a sand- 

 bath until all free sulphuric acid was volatil- 

 ized, and bisulphate of soda formed. On boiling 

 out the contents with water, iridium was dis- 

 solved out as a sulphate with a deep chrome- 

 green color, while sulphate of rhodium was 

 left in combination with sulphate of soda as a 

 flesh-colored double salt. It rapidly settled as 

 a heavy powder, requiring to be boiled out with 

 water and aqua regia, and washed by decanta- 

 tion. ^ This double salt is insoluble in hydro- 

 chloric or nitric acid or in aqua regia, can be 

 heated to 250 without change, and on igni- 



tion decomposes into metallic rhodium and 

 sulphate of soda. The total quantity of this 

 double salt obtained from a kilogramme of 

 material amounted to 33.2 grammes. The 

 first precipitates obtained by sulphite of soda 

 in the cold gave the rhodium almost entirely 

 pure when treated in this way ; the subsequent 

 precipitates were very rich in iridium, and 

 yielded rhodium far purer than that pre- 

 pared by previous processes, but not quite free 

 from iridium. Hence these products obtained 

 by sulphuric acid, which were not yet quite 

 pure, and were recognized by their brownish 

 tint, were collected, the rhodium separated by 

 ignition, and the metal obtained heated once 

 more with chloride of barium in a current of 

 chlorine to purify it a second time by the 

 method already described. The green solution, 

 free from rhodium, but containing all the irid- 

 ium, was freed from sulphuric acid by heating 

 it, first in a platinium dish over an open fire, 

 then at a gradually increasing temperature in 

 a sand-bath ; the crucible with its contents 

 was finally strongly heated in a charcoal fire, 

 by which neutral sulphate of soda and sesqui- 

 oxide of iridium were formed. The latter re- 

 mained as a black powder after boiling out the 

 fused mass, and was easily washed by decan- 

 tation. According to these experiments there 

 were obtained from a kilogramme of residues 

 the following products: 



Grammes. 



Chloride of potassium and platinum 11?. 5 



Iodide of palladium 77.0 



Chloride of potassium and palladium .... 19.0 



Sulphate of rhodic oxide and soda 33.2 



SescLuioxide of iridium 9.1 



Iridium containing ruthenium 4.5 



Vanadium. This metal (so called) was the 

 subject of a paper read by Mr. Henry E. Eoscoe, 

 before the Eoyal Institution of Great Britain, 

 in February, 1868. It derives its name from 

 Vanadis, a cognomen of the Scandinavian god- 

 dess Freia. Sefstrom first discovered it in 1830 

 in the celebrated Swedish bar iron made from 

 the Taberg ore. * From this source, when using 

 many pounds of the iron, Sefstrom obtained 

 only minute quantities of the new substance, 

 but he found it in somewhat larger amount in 

 the slag or cinder produced in the reduction of 

 the iron ore. He ascertained some of the 

 most peculiar characteristics of the substance, 

 proved it to be a new element, and prepared 

 some of its compounds in a pure state. Ber- 

 zelius still further investigated vanadium in 

 1831. Since the time of Berzelius, vanadium 

 has been discovered in many minerals, of 

 which a lead ore containing lead vanadate, 

 and called by the mineralogists vanadinite, is 

 the most important. It has also been found in 

 many iron ores, in clay, bricks, and even in 

 caustic soda. Still, the quantity of the sub- 

 stance obtained from all these various sources 

 has been extremely small ; so much so, that 

 the vanadium compounds must be reckoned 

 amongst the chemical rarities, and they aro 

 quoted in the price list of dealers in chemicals 



