CHAMBERS'S INFORMATION FOR THE PEOPLE. 



of mercury) by several processes, all of which have 

 for their object the removal of the sulphur and the 

 distillation of the liberated quicksilver, in a furnace 

 with several condensing chambers. Simple roast- 

 ing will eliminate the sulphur, or it can be removed 

 by the use of fluxes as lime or iron scales. The 

 mercury is afterwards purified from foreign metals 

 by redistillation, either alone, or with one-tenth of 

 its weight of cinnabar. Mercury is known to be 

 pure by its not yielding any black powder when 

 agitated in a bottle with dry air ; by its not drag- 

 ging a tail, when run down a gentle incline ; and 

 by certain chemical tests. At ordinary tempera- 

 tures mercury is liquid, but it freezes between 39 

 and 40 F* in which state it can be cut with 

 a knife, and is malleable and ductile. In lustre 

 and colour it resembles polished silver, and re- 

 mains untarnished for any length of time in air, 

 oxygen, and many other gases. Nitric acid, both 

 when cold and hot, dissolves mercury ; strong sul- 

 phuric acid also acts upon it when heated ; but 

 hydrochloric acid has no action upon it in either 

 condition. Mercury is employed, as already 

 stated under Gold and Silver, in extracting these 

 metals from their ores by amalgamation. Many 

 of its amalgams, as the alloys of mercury are 

 termed, are employed in the arts. Those of gold 

 and silver are used for gilding and silvering, but 

 much less than formerly, since the introduction 

 of the electro-deposit process. The use of tin- 

 amalgam in ' silvering' mirrors has been already 

 referred to. Several others are used by dentists 

 for stopping teeth, the chief being an amalgam 

 of tin and cadmium ; another of tin, silver, and 

 gold ; and another of copper. Sodium-amalgam 

 is now often used instead of quicksilver alone in 

 the treatment of gold ores. Metallic mercury is 

 of great service in the construction of barometers 

 and thermometers, as well as many other pieces 

 of philosophical apparatus. The beautiful pigment 

 vermilion is an artificial sulphide of mercury pre- 

 pared by triturating the metal with about one- 

 sixth of its weight of sulphur during the application 

 of a gentle heat. The mass is then sublimed and 

 afterwards levigated with water. Corrosive sub- 

 limate or perchloride of mercury is used as an anti- 

 septic for dry-rot in timber, and for mildew in ropes 

 and sails. It is the most powerful agent for de- 

 stroying moth -eggs in animal substances. Both it 

 and calomel, the chloride, are used in medicine. 

 It is as well to state that corrosive sublimate 

 especially is very poisonous. 



Antimony. 



Basil Valentine discovered this useful metal about 

 1490. Antimony is found native, but for commer- 

 cial purposes it is obtained almost entirely from 

 stibnite or gray antimony, a crude sulphide of the 

 metal. This ore, although found in Cornwall, Dum- 

 friesshire, and Ayrshire, is not mined in Great 

 Britain. Considerable quantities are, however, im- 

 ported into the United Kingdom, chiefly from 

 Borneo, although it is found elsewhere. Crude 

 antimony, or regulus of antimony, is the native sul- 

 phide after it has been melted in a retort or rever- 

 beratory furnace, and the earthy impurities, which 

 float on the surface, removed. From this purified 

 sulphide the metal is obtained by heating it with 

 carbonate of potassium. Metallic antimony is 

 now, however, produced in some localities direct 



414 



from the ore by smelting it in crucibles with 

 alkaline slag and scrap-iron. 



Antimony is scarcely ever used alone in the 

 arts, but its alloys and compounds have several 

 important applications. A good type-metal is 

 formed of 6 parts of lead and 2 of antimony, but 

 the proportions vary, and sometimes bismuth is 

 added. Common stereotype metal consists of 6 

 parts of lead and i of antimony, and an alloy of 

 these two metals also yields the plates on which 

 music is engraved. Britannia metal, it is stated 

 by a large Birmingham manufacturer, usually 

 consists of 90 parts of tin, 8 of antimony, and 2 of 

 copper, bismuth being now rarely added. In these 

 alloys, the use of the antimony is to impart haul- 

 ness, and in the case of type-metal it also confers 

 the property of expanding during solidification, 

 thus causing the types to take a very sharp im- 

 pression from the moulds into which they are cast. 

 Antimony itself, in its ordinary commercial state, 

 is a beautifully crystalline metal, bluish-white in 

 colour, and so brittle that it can easily be reduced 

 to powder. It does not oxidise in either moist or 

 dry air, nor do the mineral acids in their simple 

 state attack it very readily. Antimoniate of lead 

 forms the useful pigment Naples yellow ; and 

 yellow colours on porcelains and enamels are like- 

 wise formed by oxide of antimony along with 

 oxide of lead or oxide of zinc. The use of anti- 

 mony for pottery glazes is very ancient, it being 

 found on Assyrian and Babylonian ware. Some 

 compounds of antimony are valuable medicines. 



Arsenic. 



The compounds of arsenic have been long 

 known, although the metal itself was not dis- 

 covered till 1733. We have already seen that 

 arsenious acid, the chief form in which arsenic 

 occurs in commerce, is obtained as a secondary 

 product in the smelting of tin. It is also obtained 

 as a by-product in reducing cobalt and nickel 

 ores. Many ores, indeed, contain arsenic in 

 notable quantity, and large quantities of it are 

 annually wasted in roasting pyrites for the manu- 

 facture of sulphuric acid. Native arsenic occurs 

 to a not inconsiderable extent in Bohemia, Saxony, 

 and other places in Central Europe, and so also 

 does arsenical pyrites, the sulphide of iron and 

 arsenic. Metallic arsenic is obtained either from 

 arsenical pyrites or arsenious acid by sublimation in 

 close vessels so as to exclude air. Arsenious acid, 

 or the trioxide of arsenic, called also white arsenic, 

 or simply arsenic, when produced directly from 

 arsenical substances, is obtained by heating them 

 in a subliming furnace connected with a series of 

 condensing chambers, termed a 'poison tower.' 

 The fume which condenses in the chambers is an 

 impure arsenious acid in the form of a gray 

 powder. This is refined by repeated sublimations 

 in cast-iron pans surmounted by metal cylinders, 

 and finally converted into arsenical glass, which, 

 when pounded, furnishes the arsenious acid of 

 commerce. When first produced, this glass is a 

 beautiful substance, clear and colourless, but 

 becoming opaque on keeping. The workmen who 

 remove the arsenious acid from the flues, as well 

 as those who grind and pack it, are liable to a 

 disagreeable eruption of the skin. All the opera- 

 tions connected with so highly poisonous a sub- 

 stance as white arsenic are necessarily dangerous, 



