74 



METALS. 



Meit. occasionally silver. The assay, with the view of as- 

 ""V" ' certaining the quantity of antimony, is however easily 

 performed, by digesting the sulphuret in nitric acid. 

 After the action has ceased, the solution is poured off, 

 and the insoluble residue is dissolved in nitro-muriatic 

 acid. To the solution a large quantity of water is add- 

 ed, and the precipitate thrown down, is mixed with 

 twice its weight of "crude tartar and a little nitre, and 

 exposed to heat, by which the antimony is obtained in 

 the metallic state. 



METALS. The metals, if we except the bases of 

 the alkalies, and earths, are distinguished by hardness 

 and tenacity, great specific gravity, opacity, and pecu- 

 liar brilliancy, generally termed metallic lustre. 



The properties of the metals have been already de- 

 scribed in the article CHEMISTRY. At the time when 

 that article was written they amounted to 27. 



Selenium. 



1 Iron. 

 Copper. 

 Lead. 



Zinc. 

 5 Tin. 

 Mercury. 

 Antimony. 

 Arsenic. 

 Manganese. 

 10 Gold. 

 Silver. 

 Platinum. 

 Iridium. 

 Osmium. 



15 Rhodium. 



Palladium. 



Bismuth. 



Cobalt. 



Nickel. 

 20 Molybdena. 



Tellurium. 



Chromium. 



Titanium. 



Tungsten. 

 25 Tantalum. 



Cerium. 

 27 Uranium. 



Since then three new metals have been discovered, 

 and an account has been given of a fourth, of the ex- 

 istence of which, however, considerable doubts are en- 

 tertained. 



The three first are Selenium, 

 Cadmium, 

 Wodanium. 

 The other is Vestium, or Sirium. 



Selenium. 



The sulphur procured from the pyrites of Fahlun, 

 when employed in the preparation of sulphuric acid, 

 was observed by Bjuggren to leave a reddish brown 

 substance, which, by some chemists, was supposed to 

 contain arsenic ; on which account the use of the py- 

 rites of Fahlun was discontinued. Berzelius has sub- 

 jected this brown matter to analysis, and has discover- 

 ed, that besides iron, copper, lead, zinc, tin, mercury, 

 and arsenic, it contains a peculiar substance, possessed 

 of metallic properties, to which he has given the name 

 of selenium, (from selene the moon,) to recal its ana- 

 logy with tellurium, which it very much resembles. 



Berzelius, in his analysis of the brown matter, left 

 after the preparation of sulphuric acid, digested it in 

 nitro-muriatic acid. Water and sulphuric acid were 

 then added ; and the mixture was filtered, by which 

 sulphur and sulphate of lead were separated. To a 

 portion of the filtered fluid ammonia was added, which 

 threw down a precipitate, which, when heated with 

 potassium, was decomposed with ignition. This pre- 

 cipitate was partly soluble in water ; the solution ac- 

 quired a brown colour ; and, on the addition of nitric 

 acid, deposited a reddish substance, which, when 

 brought in contact with flame, communicated to it a 

 blue .tinge, and emitted the odour of horse-raddish. 

 This made Berzelius suppose that it contained tellu- 



rium ; but he afterwards found that it was caused by 

 the new metal. When the fluid which had yielded 

 the precipitate on the addition of ammonia was sub- 

 jected to distillation, a yellowish liquid was collected, 

 which contained sulphurous acid, and deposited a 

 brown powder. A black substance was sublimed into 

 the neck of the retort. The fluid, when boiled, de- 

 posited more of the brown powder ; and the sublimate 

 when washed, afforded the same matter. These were 

 selenium. 



To procure selenium free from the other substances 

 contained in the pyrites, Berzelius passed sulphuretted 

 hydrogen through the fluid obtained by filtration, after 

 the digestion of the substance in nitro-muriatic acid. 



a By this means, an orange-coloured precipitate was 

 produced, which was treated with nitro-muriatic acid. 



b Water was added to the solution, which occasioned 

 a copious white precipitate. 



c This, when heated to redness, yielded a crystalline 

 sublimate, having a strong acid taste ; and when sub- 

 jected to heat with soda and borax, it left a metallic 

 button, possessing the properties of tin. It was there- 

 fore an oxid of tin, in union with the sublimed acid, 

 which Berzelius found was an acid of selenium. 



d To the liquid from which the above precipitate 

 was obtained, muriate of baryta was added, which 

 threw down the sulphuric acid. The fluid, after fil- 

 tration, being subjected to heat, afforded a white crys- 

 talline sublimate, and a whitish matter was left be- 

 hind. 



e The sublimate (d) was an acid having a metallic 

 taste, communicated to it by mercury ; for when pre- 

 cipitated by potassa, it yielded mercury on the appli- 

 cation of heat. What remained was potassa in union 

 with the acid. 



/ This, when mixed with muriate of ammonia, and 

 distilled, first yielded water and ammonia. Selenium 

 then sublimed in small quantity. The residue, when 

 washed, left a coarse brown powder, which was sele- 

 nium, and which was sublimed to free it from impu- 

 rities. 



gThe substance left after the distillation (rf) was 

 found to consist of baryta, copper, and tin, in union 

 with the acid of selenium, and of arseniate of baryta. 



Selenium is of different colours, according to the 

 mode in which it is prepared. After being fused, it 

 has a deep brown colour, and metallic lustre. When 

 allowed to cool slowly, its surface becomes rough. In 

 the former case, the fracture is conchoidal, and pre- 

 sents the appearance of lead ; in the latter it is granu- 

 lar, and resembles a piece of cobalt. 



When, on the contrary, selenium is precipitated from 

 some of its combinations, it assumes a cinnabar-red 

 colour ; and in some particular cases, the colour ap- 

 proaches that of gold. When selenium is in powder, 

 it is red ; but when pounded, it sticks together, and 

 becomes grey. 



The specific gravity of selenium is 4.32. It is a 

 bad conductor of caloric ; a small piece of it, which is 

 heated to near the fusing point at one end, may be 

 held by the other end in the hand. It is a very im- 

 perfect conductor of electricity, and what is remark, 

 able, it has not been made electric by friction. 



When selenium is heated to 212, it becomes semi- 

 liquid, and, at a few degrees higher, it fuses. As it 

 cools, it becomes semifluid, and then passes into the 

 solid form. When semifluid, it may be drawn into 

 fine threads, or beat into plates, which, when thin, are 

 transparent. These, when viewed by transmitted light, 



Metala. 



