CHEMISTRY. 



19 



Elements 

 of 



tr ^' 



Alloys. 



of grains, breaks under the hammer, but may be cut 

 with a knife. It is composed of four parts of silver 

 and one of phosphorus. Heat decomposes it, by dis- 

 sipating the phosphorus. 



4. Silver docs not combine with azote. 



5. It combines readily with most of the metals. 

 When gold and silver are melted together, they 



combine spontaneously, in the proportion of one part 

 of silver and five ot gold. They may, however, be 

 melted together, and mixed in any proportion what- 

 ever. This alloy is harder and more sonorous than 

 pure gold. Its hardness is a maximum when the al- 

 loy consists of two parts gold and one silver. The 

 density of the alloy is a little diminished, and the co- 

 lour of the gold is much altered, even when the pro- 

 portion of silver is small. It is not only pale, but has 

 a very sensible greenish tinge. 



Silver and platinum may be combined by fusion, 

 and form a hard alloy, not so ductile as silver. The 

 two metals separate when the alloy is kept in fusion. 

 Hence there appears but little affinity between them. 



SECT. IV. Of Mercury. 



Mercury, called also quicksilver, was known to the 

 ancients, and applied by them to the same purposes 

 as it is by the moderns. 



Properties. 1. Its colour is white, like that of silver ; it has a 

 good deal of lustre, and is destitute of taste and smell. 

 Its specific gravity i 13.568. At the common tem- 

 perature of the atmosphere, it is always in a state of 

 fluidity. But if it be cooled down to 39 below ze- 

 ro, it becomes solid like any other metal. The con- 

 gelation of mercury by cold was accidentally disco- 

 vered by Professor braun, at Pctersburgh, in 17.59. 

 The freezing point was ascertained by Mr Hutchins, 

 at Hudson's Bay, in consequence of the directions of 

 Mr Cavendish. Solid mercury is malleable ; but nei- 

 ther the degree of its malleability nor its ductility- 

 have been ascertained by experiment. Mercury boils 

 when heated to 656. Its vapour is invisible and 

 elastic like air. It may be easily distilled over in pro- 

 per vessels, and by this means is obtained pure. 



2. Mercury is not altered by being kept in water. 

 But when long agitated in air, or when kept heated 

 in the open air, it gradually loses its metallic appear- 

 ance, and is oxidized. Only two oxides of mercury 

 have been yet ascertained in a satisfactory manner, 

 the protoxide, which is black, and the peroxide, which 

 is n'd. 



The protoxide is a black powder, which may be 

 obtained by agitating mercury for a long time in a 

 gtout phial ; or by heating the salt called calomel, or 

 muriate iifmercuri/, with a solution of potash. It is 

 black, insoluble in water, and contains about 5 per 

 cent, of oxygen. 



The red oxide, called also red precipitate, may be 

 obtained by k -eping mercury for several days, nearly 

 at the boiling point, in a tall glass vessel, so contrived 

 as to prevent the evaporation of the mercury, and ad- 

 mit a communication between the interior ot the ves 

 el and the atmosphere. The mercury becomes at 

 first black, and gradually changes to red. It may be 

 formed more speedily ind easily by dissolving mercury 

 in nitric acid, evaporating the solution to dryncss, 



and heating the dry salt gradually, almost to redness, Elements 

 in a crucible or capsule. Nitric acid fumes exhale, / 

 and the whole assumes a fine red colour. The red Chemistry, 

 oxide of mercury has an acrid and disagreeable taste, 1 "~" P ~<"" 1 **' 

 acts as an escharotic, and possesses poisonous qualities. 

 When heated with zinc or tin tilings, it sets them on 

 fire. It contains about 10 per cent, of oxygen. 

 When heated it gives out oxygen gas, and the mer- 

 cury is reduced. 



3. Mercury does not combine with hydrogen or 

 carbon ; but unites readily with sulphur and phos- 

 phorus. 



When two parts of sulphur and one of mercury Sulphurcts. 

 are triturated together in a mortar, they gradually 

 assume the appearance of a black powder, formerly 

 called oet/ihps mineral. The same compound is form- 

 ed by adding mercury slowly to its own weight of 

 melted sulphur. When formed by the first process, 

 the powder is black, but a microscope detects in it 

 mall globules of mercury ; when formed by the se- 

 cond process, the powder is black, with a shade of 

 purple. This compound has been ascertained to con- 

 gist of mercury and sulphur united together, in what 

 proportion is not well known. 



When this black sulphuret is exposed to a red heat 

 in a glass vessel, it sublimes and forms a cake of a fine 

 scarlet colour. In this state it is usually called cin- 

 nabar, and when reduced to a fine powder, vermilion. 

 It is well known as a red paint. Its specific gravity 

 is about 10. It is tasteless, insoluble in water and in 

 muriatic acid. When suddenly heated it burns with 

 a blue flame. When mixed with iron filings, and dis- 

 tilled, it is decomposed, and running mercury obtain- 

 ed in the receiver. It is composed of about Sj parts 

 mercury and 15 sulphur. 



When phosphorus is mixed with the black oxide 

 of mercury, and exposed to heat, the mixture readily 

 combines, forming a black mass, which seems to be 

 phosphureted oxide of mercury. At least phosphorus 

 and mercury do not unite when heated together. 



4. Mercury does not unite with azote. 



5. It combines with most metals, and forms com- Amalgams, 

 pounds called amalgams. 



The amalgam ot gold is formed very readily by 

 throwing small pieces of red hot gold into hot mer- 

 cury. The two metals combine in any proportion. 

 The amalgam is white and fluid if the mercury ex- 

 ceed. But by squeezing it through leather, the ex- 

 cess of mercury separates, and a solid amalgam re- 

 mains, of the consistence of butter, which gradually 

 crystallizes. It consists of one part of mercury to 

 twu of gold. This amalgam is much used in gilding. 



The amalgam of platinum may be formed by tri- 

 turating the powder of platinum with mercury, add- 

 ing gradually a portion of either ingredient, till the 

 combination is completed. When the process of 

 amalgamation is once begun, it goes on easily. This 

 amalgam has the consistence of butter, a white colour, 

 much lustre, and does not tarnish by keeping. The 

 mercury may be driven off by heat. 



The amalgam of silver may be made in the same 

 manner as that of gold, and with equal ease. It hag 

 a white colour, is always soft, and crystallizes. 



Al. these amalgams are decomposed, and the mer- 

 cury driven off by heat. 



