SILVER. 



263 



than a grain. The theory of its detonation is con- 

 sidered as similar to that of fulminating gold; it 

 probably consists of oxide of silver and ammonia, 

 the elements being united by affinities so nicely 

 balanced, that the slightest external force subverts 

 them, and causes new combinations: the oxygen of 

 the oxide unites with the hydrogen of the ammonia, 

 and forms watery vapour; the nitrogen must assume 

 the elastic form, and the augmentation of elasticity i 

 in these products, by the caloric suddenly extri- 

 cated, may be the cause of the detonation. A ful- 

 minating silver totally different from that above 

 described, is frequently sold as an object of amuse- 

 ment: it is enclosed between the folds of a card 

 cut in two lengthways, the powder being placed at 

 one end, and the other being notched, that it may 

 be distinguished; if it be taken by the notched end, 

 and the other be held over the flame of a candle, 

 it soon detonates with a sharp sound and violent 

 dame ; the card is torn and changed brown, and the 

 part in contact with the composition is covered 

 with a slight metallic coating of a grayish-white 

 colour. This compound is formed in the following 

 manner: Into a pint tumbler, or other glass vessel, 

 is introduced 100 grains of dry nitrate of silver, 

 over which is poured one ounce of alcohol, and the 

 same quantity of smoking nitric acid. The mix- 

 ture of the alcohol and nitric acid occasions much 

 heat and effervescence in the liquid : if this is so 

 violent as to overflow the vessel, cold alcohol is 

 added in small portions to abate the ebullition : in 

 a few minutes the liquor becomes turbid, and a very 

 heavy, white, crystalline powder falls down, which 

 is separated by the filter, and thoroughly washed 

 with tepid water: before being fully dry, it should 

 be separated into parcels of ten or twenty grains, 

 which portions, when thoroughly dried at a distance 

 from the fire, present the following properties: 

 The substance is white and crystalline; the light 

 changes its colour to a dark brown; when heated, 

 it explodes with great violence. It explodes also 

 by percussion and friction, and the contact of sul, 

 phuric acid. When put into dry chlorine gas, it 

 explodes with a loud report. So powerful is this 

 powder in its explosion, that no person but chemists j 

 should venture upon its manufacture, or presume 

 to experiment with it. The most painful accidents 

 have repeatedly occurred with it, in the hands of 

 the inexperienced and the careless. It is composed 

 of oxide of silver 14-75, and of a peculiar acid, 

 called the fulminic, 5-25. For some account of 

 fulminic acid, see Prussic Acid. 



Silver Ores There are five important ores of 

 silver, viz. 1. Native silver; 2. vitreous silver 

 (or silver glance); 3. black silver; 4. red silver; 

 5. horn silver. 



Native silver is occasionally found crystallized in 



the following shapes, viz the cube, octahedron, 



tetrahedron, rhombic dodecahedron, trapezohedron, 

 ;md six-sided tables. The cube is the primitive 

 form; but it more often occurs in dentiform, fili- 

 form, and capillary shapes; also reticulated, arbo- 

 rescent, and in plates; likewise in plates, formed 

 in fissures, and in superficial coatings; cleavage 

 none; fracture hackly; lustre metallic; colour 

 silver-white, more or less subject to tarnish; 

 streak shining; ductile; hardness between gypsum 

 and calcareous spar; specific gravity, 10-47. Na- 

 tive silver has been distinguished into common and 

 auriferous native silver- the former consists of 

 silver alloyed with a small proportion of antimony, 

 irsenic, iron, &c. ; the latter frequently contains 



fifty per cent, of gold. Native silver occurs princi- 

 pally in veins, traversing gneiss, clay-slate, and 

 other primitive and transition rocks. There are 

 but few countries in which it is found in any con. 

 siderable quantity. Among these are the mining 

 districts of Saxony and Bohemia, also Norway and 

 Siberia, but particularly Mexico and Peru. 



Vitreous silver presents itself crystallized in 

 cubes, octahedrons, and rhombic dodecahedrons. 

 Its primitive form is the cube. It also occurs in 

 reticulated, arborescent, dentiform, and capillary 

 shapes ; also massive and impalpable ; fracture im- 

 perfect, and small conchoidal, uneven ; lustre 

 metallic, subject to tarnish; colour blackish lead- 

 gray; streak shining; malleable; hardness about 

 that of gypsum; specific gravity, 7'19. It consists 

 of silver 85-0, sulphur J5-0. It is easily fusible 

 before the blow-pipe, and intumesces; but it gives 

 a globule of silver by a continuation of the blast. 

 It has been hitherto found almost exclusively in 

 veins, along with ores of lead, antimony, and zinc. 

 It occurs in Saxony, Bohemia, Hungary, Mexico, 

 and Peru. It is an important species for the ex- 

 traction of silver. 



Slack silver has for its primitive form a right 

 rhombic prisrn of 100 0'. The crystals, however, 

 are not often observed; but it is more frequently 

 in granular masses; fracture imperfect conchoidal, 

 uneven ; lustre metallic ; colour iron-black ; streak 

 unchanged; sectile; hardness about that of gyp- 

 sum; specific gravity 6-2. It consists of 



Silver, 



Antimony . 



Iron. 



Sulphur, 



Copper and arsenic, 



65-50 

 Kill!) 

 SCO 

 1200 

 50 



93-00 



Before the blow-pipe, upon charcoal, it yields a 

 dark-coloured, metallic globule, which may be 

 reduced with saltpetre. It is found in silver veins 

 along with other ores of silver. It occurs chiefly 

 in Saxony, Bohemia, and Hungary, in Mexico and 

 Peru. It is a valuable ore for the extraction of 

 silver. 



Red silver. The primitive form of this species 

 is an obtuse rhomboid of 109 28'. Its secondary 

 forms are six-sided prisms, variously truncated and 

 acuminated, and an equiangular double six-sided 

 pyramid; cleavage parallel with the sides of the 

 primitive form, pretty distinct; fracture conchoidal ; 

 lustre adamantine; colour iron-black to cochineal 

 red ; semi-transparent to opaque ; sectile ; hardness 

 about that of gypsum ; specific gravity 5-84. The 

 crystals are very liable to occur twin-shaped. 

 Red silver is often found massive, granular, arid 

 even impalpable. It consists of 



Silver, . 



Antimony, 

 Sulphur, 



58-949 

 22-846 

 16-609 



It decrepitates before the blow-pipe upon charcoal, 

 melts, and emits fumes of sulphur and antimony, 

 after which it yields a globule of silver. Red 

 silver is confined to a small number of localities, 

 and occurs in veins along with other ores of silver, 

 galena, and blende. It is found in the metalic, 

 veins near Freiberg, also at Marienberg, Annaberg-. 

 Schneeberg, and Johanngeorgenstadt in Saxony; 

 likewise in Bohemia, Hungary, Dauphiny, and 

 Norway; but is much more abundant in Mexico 

 and Peru. It is a valuable ore for silver. 



Horn silver has the cube for its primitive form, 

 in w r hich shape it frequently emirs, as also iu 



