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diffufed in the mafs. By making the experi-ment in a glafs retort, and a proper apparatus,the fait will be found to give out nitrous gas,oxygen, a little azot, and at laft nothing re-mains but the filver, very pure, white, andductile. If a piece of this fait be laid on redhot charcoal it deflagrates like common nitre,and when this is over, the charcoal is coveredwith a ftrongly adhering coat of filver, whichby a little rubbing appears of its natural co-lour.

The compofition of nitrat of filver is givenby Prouft, as follows: ioo parts of the fufednitrat decompofed by heat leave 64 of purefilver, whence too parts of filver would form140 of the nitrat. On the other hand 100parts of filver unite with 9.5 of oxygen whenoxydatcd in the degree in which the metal exiltsin the nitrat, whence 100 parts of the nitratwould be compofed of about,

Silver 64 \

Oxygen 6 j '

Nitric acid - 30

100

The a&ual quantity of lapis infernalis ufu-ally obtained from filver is about 13 drachmsfrom 8 drachms of pure filver, but only 10 or11 drachms from the fame quantity of ftandardfilver. q

Nitrat of filver detonates mod violently withphofphorus. If a fmall cryftal of nitrat of filveris laid on an iron anvil, and about half a grainof phofphorus is put upon it and itruck fmartlywith a hammer it explodes with a very violentreport. A greater quantity of thefe materialsmight be dangerous to the operator. The ironis found after the explofion covered with minuteparticles of metallic filver.

Phofphorus will alfo reduce the nitrat offilver in the moift way. Put a ftick of newlymelted phofphorus into a very dilute folutionof nitrat of filver, and in half a day it will befilvered on its furface, and gradually the wholeof the filver precipitates on the phofphorus infine dendritic cryltals.

Hydrogen alfo rapidly reduces the nitrat offilver, and during its reduCiion it pafl'es throughvarious fhades of brown, till it acquires themetallic luftre. A coating of filver may bethus fixed on filk, as Mrs. Fulham has obiervedin her ingenious experiments/ by moiftemngthe filk and expofing it while wet to a currentof hydrogen gas. Thus placed, the filk be-1 Beanmc. ' Etuy on Corobuilio

comes gradually brown, and as the mlu&iooadvances the furface is covered with an irides-cent pellicle of various colours whilft a firmcoating of filver fixes to the threads. It wasfound impracticable however to produce anuniform perfect filvering by this method, forthough many particles of bright white metalmay be obferved, the general appearance istarnifhed and void of luftre.'

Nitrat of filver is alfo reduced very readilyupon charcoal by the fun’s rays, or by expofureto a heat of boiling water without the affift-ance of light. This reduction forms fomebeautiful experiments, which are given byCount Rumford. 5 Some charcoal was fivftboiled for fome time in diftilled water, till ithad become fo much wetted as to fink in thisfluid. A piece of it was then introduced intoa phial containing a moderately dilute folutionof nitrat of filver in diftilled water (this faithaving been previoufly fufed and reduced tothe ftate of lapis infernalis to drive off whatlittle excefs of acid the cryftailized fait mightcontain) and it was fet in a ftrong fun-Ihine.In lefs than an hour fmall fpecks of revivedfilver appeared on the charcoal, and this depofi-tion of filver continued till the charcoal wascovered with fpangles of reduced filver per-fectly white and refplendent. The fame expe-riment was repeated with the difference thatthe phial was inclofed in a tin box and expofedfor an hour to the heat of boiling water in acommon fteamer ufed for boiling potatoes.When examined, the furface of the charcoalwas covered with a raoft beautiful metallic ve-getation, fmall filaments of revived filver re-fembling fine flatted wire pufhing out from thefurface in all directions, and extending to thediftance of a tenth of an inch.

Silver is precipitated from its nitric folutionby mercury. If the folution contains both fil-ver and mercury, and the precipitating metalbe alfo a compound of mercury and filver, acurious and beautiful precipitation of a brilliantalloy of thefe two metals is depofited in anarborefcent form which has been called theArbor Diana or Silver Tree. Lemery was thefirft who obferved this curious metallic vegeta-tion, and various proportions of the ingredientshave been given by different chemifts, all ofwhich fucceed to a certain degree. The modeffential point feems to be, that in the folutionthe filver fhould much exceed the mercury,but in the precipitant the mercury ftiould ex-ceed the filver. The proportions given by

- * Phil. Tram", vol, 88, p. 460*