SILVER. 



thefe frequently detonate with fuch violence, as to break tlie 

 vcflel in which they are contained. 



The theory of theie appearances is obvious ; the oxygen 

 of the filver combines with the hydrogen of the ammonia, 

 forming water, which, with the azotic gas of the fame, are 

 in an inilant rendered fo highly elaltic by the caloric fct 

 free, as to produce theexploiive efFeft fo confpicuous in this 

 fubftance. It is needlefs to fay that the filver is left in the 

 metallic form. 



Nitrate of filver is decompofed by all thofe metals having 

 a fuperior attraftion for oxygen. The oxygen of the filver 

 is given to the decompofing metal, which alfo combines with 

 the acid. Copper, fo employed, precipitates the filver in a 

 white metallic powder, the refult being nitrate of copper in 

 the place of nitrate of filver. The precipitate is not pure 

 filver, fome copper will always be deteftcd when the preci- 

 pitate is re-diilolved. 



Mercury has alfo the property of precipitating filver from 

 the nitrate, producing the appearance which has been termed 

 the arbor Diana. Lemery recommends one part of filver to 

 be dilfolvcd in nitric acid, and the folution to be then diluted 

 with twenty parts of dillilled water : to this add two parts 

 of mercury. The mercury gradually occupies the place 

 of the filver, and the latter is precipitated in the form of 

 vegetation, from which the name has been derived. 



The vegetative appearance is caufed by the growth of the 

 cryitals being from the extreme points ef that already formed, 

 as is the cafe with the grownh of vegetables. Tiie mercury, 

 and the fmallefl portion of precipitated filver, form a Gal- 

 vanic combination. The filver now in folution is reduced 

 upon that already formed, in confeqiience of its ilate of 

 eledricity being negative, that of the mercury being rela- 

 tively pofitive, by which it attraAs the acid. This procefs 

 would doubtlefs be facilitated by dropping a fmall bit of me- 

 tallic filver upon the mercury, added to nitrate of filver. This 

 would form a Galvanic combination, and the bit of filver 

 would become an immediate rallying point for the filver in 

 folution. If a little of a dilute folution of nitrate of filver 

 be Ipread upon a pane of glafs laid in an horizontal pofition, 

 and a common pirr be laid in the middle of the covered part, 

 in a few hours, beautiful ramifications of filver extend from 

 every fide of the pin ; fometimes to the diltanceof an inch. 

 This is alfo to be explained by Galvanifm. 



Muriate of Silver. — When muriatic acid, or any foluble 

 muriate, is added to nitrate of filver, a denfe and blueifli- 

 white precipitate is thrown down, which is muriate of filver. 

 Although white when it is juft precipitated, it foon affumes 

 a purple tint by expofure to the light, and the change is 

 quicker as the light is more intenfe : hence this fubltance has 

 been employed to meafure the degree of intenfity of light, 

 by the time in which the change of colour takes place. 



It may be faid to be infoluble in water : this property, and 

 its confpicuous appearance in other refpedls, renders the ni- 

 trate or hilphate ,1 filver fo valuable as a teil for nuiriatic 

 acid. The latter, on combining with the filver, forms the 

 fait in queftion. 



M''licn this fait isexpofed to heat, it eafily melts : on cool- 

 ing, it becomes folid. It is a femi-tranfparent mafs, of a 

 grey colour, and of a horny appearance, from which it has 

 been c: '''d luna cornea, or horn-filver. If fufed with a great 

 heat in a crucible, it becomes fo thin a fluid as to fink througli 

 the pores of the crucible. It is not decompofed by any of 

 the acids nor the alkalies, but when heated with the carbo- 

 nates of potadi or foda, the acid is difengaged. It diifolves 

 in caullic ammonia, forming a tranfparent lolution : this, by 

 expofure to the air, undergoes confiderable change. A pelli- 

 cle forms on the furface, wliich is firft of a blueidi colour, 



and ultimately black. This pellicle, on examination, is 

 found to be muriate of ammonia and reduced filver. Thofe 

 who with fir Humphrey Davy hold oxymuriatic acid to be 

 a fimple body under the name of clilorine, confider this fub- 

 ltance as a compound of the latter fubltance with metallic 

 filver. Sir Humphrey gives it the name of argeniane, and 

 Dr. Thomfon, more confiltently, chloride of fiher. 

 Tlie compofition of this fait, according to Prouft, i: 



Muriatic acid - i8 



Oxyd of filver - 82 



100 



By the atonic theory it ihould be conflituted by loc 

 + 7.5 = 107.5 °f oxyd of filver, and 24 muriatic acid, 

 which would give 



Oxyd of filver - 81.7 



Muriatic acid - 18.3 



100 



Sir Humphrey confiders it as a compound of one propor-* 

 tion of chlorine, 67, and one proportion of filver, 205, 

 which will give 



Silver - - - 75.3 



Chlorine - - 24.7 



100 



Confidcnng the 24.7 of chlorine as oxymuriatic acid, which 

 would be 18.8 muriatic acid, and 5.9 oxygen ; then giving 

 this oxygen to 75.3 of filver, would give 81.2 of oxyd of 

 filver, and 18.8 of muriatic acid in the 100, which nearly 

 agrees with the above. The property which this fait has of 

 becoming black by the adlion of light, has rendered it ufeful 

 for marking linen. Very improper ingredients have been 

 fold for this purpofe. The nitrate of filver is employed to 

 write with upon the linen, which is very proper ; but the 

 part is often prepared by a folution of loda or potafli, in- 

 itead of a folution of muriate of foda (common fait). The 

 following will be a recipe which caiuiot fail of luccefs : dif- 

 folve 30 grains of lunar caullic in one ounce of diftilled 

 water ; this will be for the writing liquid. For the pre- 

 paring liquor, diifolve half . an ounce of common fait in four 

 ounces of water ; and in the lame dillolve half an ounce of 

 gum arabic. Moiiten the part to be marked with the latter, 

 and dry it till the writing will not run. The letters will firll 

 appear of a blueifii-white, but become perfeftly black by cx- 

 polurc to light. 



The fluate, borate, phofphate, carbonate, and arfeniate of 

 filver, are infoluble powders, having no ilriking properties, or 

 but little known. The arfeniate is formed by adding arfeniate 

 of potalh to any foluble fait of filver. It falls down in the 

 form of powder of a yellow colour. Its iiifolubility, and it^ 

 confpicuous colour, have been taken advantage of by employ- 

 ing nitrate of filver a« a tell for arfenic. 



The ciiromate of filver is an infoluble fait, of a red colour ; 

 it is formed by adding chroniate of potaHi to nitrate ot 

 filver. It, however, becomes purple by expofure to air and 

 light. 



Acetate of filver is a foluble fait, formed by adding the 

 acetic acid to oxyd of filver. The folution affords prilinatis 

 cry Hals. 



The rcll of the falts are but little known. 

 SiLvtn, in Medicine, is called liimi, the moOn ; and has 

 been much extolled for its virtues by chemical writers. But 

 5 A 2 crude 



