SILVER. 



mony. The refiduum is fulphur. The muriatic folution de- 

 pofits cryftals of muriate of lead on cooling. When no more 

 cryitals fail down, thefe cryftals are to be added to thofe 

 obtained before. Thefe, being heated in an aflay crucible with 

 twice their weight of black flux, afford metallic lead. This 

 lead, however, treated in the ufual way on the cupel, affords 

 a fmall portion of filver. The folution Hill contains a fmall 

 portion of muriate of lead and the antimony. By adding a 

 folution of Glauber's fait, the lead is precipitated in the 

 Itate of fulphate, affording Aths its weight of metallic lead. 

 The antimony, which is the laft, may be precipitated by af- 

 fufion of water. The precipitate, being wafhed, dried, and 

 ignited, is the pure oxyd of antimony, yielding on its re- 

 du£tion -J-f of the metal. The analytis of the light white 

 filver-ore, by Klaproth, gives of 



97.25 



The corneous filver-ore, which is muriate of filver, is 

 eafily reduced in the dry way by fufing it with foda, ina 

 crucible capable of fufing the metallic filver. The foda 

 takes the muriatic acid, forming muriate of foda, which 

 efcapes in white fumes, and the filver is left pure. 



In the humid way, it is firft fufed in a glafs retort with 

 carbonate of potaffi. The mafs is then diflolved in hot 

 water, and the folution filtered. The refiduum is then dif- 

 folved in nitric acid, leaving behind a red powder. This 

 powder, being treated with nitromuriatic acid, leaves be- 

 hind a fmall portion of muriate of filver, which mull be 

 accounted for in metallic filver, as before direfted. Am- 

 monia, being added to the nitromuriatic folution, precipi- 

 tates a red powder, which is oxyd of iron. To the nitric 

 folution, from the mafs firft treated with carbonate of 

 potafh, muriate of foda is now to be added ; which pre- 

 cipitates the filver in the form of muriate, from which the 

 metallic filver may be either calculated, or obtained by 

 fufion with foda. The aqueous folution from the fufed 

 mafs is now to be faturated with acetic acid. If alumine 

 be prefent, it will be precipitated. The liquid part is now 

 to be evaporated to drynefs. If alcohol be added to the 

 dry mafs, it diffolves the acetate of potafh. The refiduum 

 is then diflolved in water. To thio, muriate of barytcs is 

 to be added, which, if fulphiiric acid be prefent, will caufe 

 a precipitation of fulphate of barytcs, the fulpiuiric acid 

 of which is to be confidercd as a produA of the ore, and 

 will be equal to one-third of the weight of this precipitate, 

 vshen waflied and dried. The remainder of the falinc mafs 



Vol. XXXII. 



which was diffolved in water may be confidered as muriate 

 of potalh, the acid of which is another ingredient of the 

 anaiyfis, and will be equal to ; i- of the fait. 



P/}^cal and Chemkal Properties of Silver. — Silver, when 

 pure and newly polifhed, is of a fplendid white colour, and 

 becomes more white when the polifli is deadened. Its hard- 

 nefs is nearly that of copper. Its malleability is nearly 

 equal to that of gold. At a heat vifibly red in the darky 

 it can be worked with great facility by the hammer into 

 various articles, in the manner of working iron. After 

 being rolled into very thin (heets, it can be beaten into leaves 

 of -nroVinjth of an inch in thicknefs, and can be drawn 

 into wire finer than a human hair. A wire of -ryth of an 

 inch will require 336 lbs. to break it, when exerted in the 

 direftion of its length. At a temperature fhort of red- 

 nefs, thefe pieces can be united either by the hammer, 

 "or by preffing them together with friftion by a fteel 

 bumifher. 



It melts at the temperature of 28^ of Wedgewood, or 

 4717° of Fahrenheit. If the heat be raifed the metal be- 

 comes more liquid, and boils. This is occafioned by its 

 affuming the elaftic form, in which Hate it riles, and is con- 

 denfible on the furface of bodies held over it, as has been 

 obferved with gold. 



In purifying filver on the cupel-, it is obferved, that when 

 it is removed from the furnace, and juft at the point of con- 

 gelation, a fmallexplofion enfues, giving to the furface of 

 the button an appearance as if fome elaftic fluid had been 

 difengaged from it. It has been difcOvered by Mr. Samuel 

 Lucas, of Sheffield, that the elaftic fluid which is fepa- 

 rated, producing the phenomenon in queftion, is pure oxy- 

 gen gas. 



By keepinir filver long in a ftatc of fufion, at a very high 

 temperature, it becomes oxydated. 



Macquer converted filver into a vitreous oxyd by ex- 

 pofing it to the heat of a porcelain furnace. 



Silver is readily inflamed by eleAricity, and converted 

 into an oxyd of a greenilh-yellow colour. 



The moft direft way to obtain the oxyd of filver is by 

 diffolving the filver in nitric acid, and precipitating it with 

 lime-water. The precipitate is at firft white, in which 

 ftate it may be confidered a hydrate of the oxyd. When 

 heated, the water efcapes, and it afl'umes a grecnifh-yellow 

 colour, inclining to grey. If the heat be raifed, the air 

 being excluded, the oxygen is drawn off, leaving the metal 

 in a ftate of purity : 100 parts of filver have been found to 

 contain 7.5 of oxygen ; hence, if the atom of hydrogen 

 be I, that of filver will b- 100. No combination of filver 

 with azote or carbon has as yet been difcovered. 



It combines with fulphur with great facility : the mere 

 contaft of the metal with flour of fulphur is fufficient to 

 give the furface a yellow colour. If the filver be in thin 

 plates, and ftratified in a crucible with the fame, at a red 

 heat the combination foon takes place, and ihe mafs fufcs, 

 forming a fulphuret of filver of a violet colour, fometimes 

 in cryftals of the (hape of a needle. 



This fubftance is brittle, but fufficiently foft to be cut 

 with a knife. It is decompofablc by heat. The fulphur 

 efcapes, leaving the metal in a ftatc of purity. This 

 compound is an atom of filver equal to 100, united to an 

 atom of (ulphur 15. 



Sulphurct of filver is alfo formed by expofing llie metal 

 to fulphuretted hydrogen gas. The fmall quantity of the 

 httcr exifting in the atmofphere is capable of foon com- 

 municiting a yellow, and ultimately a purple colour to 

 polifhcd filver. 



5 A Mr. . 



