Show silvering glass the tho following is an extract from a lecture by prof faraday recently delivered before the tiie royal society in which lie he explained with experiments BI Petit jeans silvering process al process consists essentially in the preparation of a solution containing ooyd of silver am m 0 illa tila nitric ana and tartaric acids able to deposit metallic silver either at common or somo what elevated temperatures 1540 grains of nitrate of silver being tre cited with 95 grains os of strong solution of ammonia and afterwards with grains of water yields a solution to which when clear grains of tartaric acid dissolved in grains of water is to be added and then 15 cubic inches more of water with good agitation when tilo tile liquid has settled the clear part is to be poured off cubic inches of water to be added to the rema remaining inin slid solid matter that as much may be dissolved us ps possible sible sibie and the tha clear didds to ba bo put together and aud increased by the tho further addition of 61 cubic inches of water this is the tile severing isI vering su lution solution ko no 1 1 A second fluid no sis ais to be prepared in like manner with this difference that the tartaric acid is to be doubled in quan quart city the tho apparatus employed for the ills silvering of glass plate consists of a casu casi iron table box containing water within aud a set of gas burners beneath bereath to heat it the upper surface of tho table is planed aud and set truly horizontal by a level heat is applied until the tha temperature is deg fall fah tile tiie glass is we well weil 11 cleaned first with a cioth cloth after wh cli eh a plug of cotton dipped in the silvering fluid and a little powder is carefully passed over the surface to be silvered and when catlon callon is dry it is removed by another plug of cotton and th the plate obtained is perfectly clean the glass is then laid on the table a portion of the silvering il vering fuld poured on to the surface and this spread carefully over every part by a cylinder of india rubber sti sli etched stretched upon wood ich has previously been cleaned aud wetted with a solution in this manner mantler a perfect wetting of the surface is chained and find bil bli air bubble bubbled 4 scare removed then more fluid is poured oil oll the glass until it is covered with a layer about 1 iio ilo 10 of hii hit an inch in ja depth which easily stands upon it and in i that state its temperature is allowed to rise in about ten minutes by the heat of warm water in the hollow bollow box odthe of tile tabie table silver sliver bagi begins us to deposit on the glass and in fifteen or twenty minutes a uniform opaque coat having a greyish grayish tint thit on the upper surface is deposited after a certa centa certain in time tile the glass employed in the illustration was pushed to tho the edge of the table tible was tilted that the fluid might be poured off then washed with water and examined the under presented a perfectly brull brUli brilliant ant metallic plate of high reflective power as high as 1113 an any that silver can attain to and the coat 0 or f silver though thin was so strom strong as to sustain handling aud and so firm as us to bear p polishing on the he back to any degree by rubbing with the tile hand and polishing polis liing powder the atthe usual course in practise ilowe however er is when the first stream of fluid is exhausted so remove it and apply a layer of no absolution and when that has been removed and the glass washed and dried to cover the back surface with a protective coat of black var varnish when the form of the he glass varies simple expedients expedient is arb aro employed and either concave convex or corrugated surfaces are silvered slivered and bottles and vases are coated coaled internally it is easy to mend an injury in the silvering of a plate and two or three cases of repair performed on the table |