G I. A S 





herd of fi-fio'.i } for, in thh cafe, tlii llroii;^ fire will J;.>IV. oy of a tranfparent red colour, hardly to be equalled by thai of 



th'- colour:'-."- fiibftaiicc before the 'i-lafs uAls, and he has rubies. Sje Porofity of Bodies, in Shaw's Abridgment of 



found taVfollowiug compolillous to be nearly the bell j I'/s. Boyle's Works, vol. i. p. 459 j and Appendix to the Scep- 



laiid tu-o parts, aKiidi three paj-ts ; or find two, alka- tic:il ChemiH. 



li tluve calcined borax one; or fand two, alkali two. About the fame time Caflius is faid to have difcovered the 



calcined borax one: and though fak-petre is hardly precipitation of gold by tin, and that glafs might be tinged 



ufed at all or very fparin<Tly, for yellow glafles, as of a ruby colour by melting it with this precipitate : thougii 



It too much volatilizes the colouring fiibftance ; yet here he does not ajipcar, fays Dr. Lewis, from his treatife De 



for the molt part a certain proportion of it, eafdy determined Auro, to have been the difcoverer of either. He defcribes 



by trial, is very necelTary ; for without it, the couceul rated the preparation of the precipitate and its ufe, but gives no 



colourin'"- matter is apt to make the glafs too dark, and even aecount of the manner of employing it ; only that he fays, 



gf an opaque pitchy blicknefs. It doe:! not certainly appear one dram of gold, duly prepared, will tinge ten pounds of 



that tilt re is any material diverfity in the effetls of different glafs. _ &ie Q,oi.-d pr.-riphnte iv'tlh tin. 



ciKils • the difference belu'; probably owir.g to the different This pruCL-i's was foon after brought to perfcftion by 



quantities of the inflammable matter which they contain; ■"' ' ' -i- /•--- -.-. c.^ :.:._._-.rm _•_. 

 fo that a little more ihall be required of one kind than of an 

 other, for producing the fame degree of colour in the glafs 

 Nor does the f .ftneis or fufibility of the frit appear to be v. 

 anv refpeCt neccffary. 



Gold-coloured fp'angles may bediffufed throng 



Kunckel ; who fays, that one part of the precipitate is fiifficient 



to give a ruby colour to 1280 parts of glafs, and a fenlible 



rednefs to upwards of 1900 parts ; but that the fucccfs is 



bv no means cor.Ilant. Kunckel alfo mentions a purple-gold 



powder, refembling that of Neri, which he obtained by in- 



_ the fub- fpiffatiiig foiutiou of gold to drynef-i, abftracting from it 



ftniTrp' of n-lafs. bv n-uxintr the yellow talcs witli powdered frelli aqua regia three or four times, till the matter appeari 

 ' .0 .'.-'■ 'I . ' ■ . r .- ^ e. !.,..,;,■„ 1:1.., ,.:i . .i.». :.,u-,-... ...:.i. a „ii- .i;..» 1.... 1 



glafs, and bringing the mi.xture i.ito fiifion. See Lewis's 

 Com. Phd. Techn. p. 223. 626, See. 



Gh.\S'. for counttrf/ilins n'p'S hizuli. See Lnph l.Azut.r. 



Glaus rcft-niMiTi^r opal. See Oi'.\J. and Ge.ms. 



Glass, Jin/')-. The way to give the true line red cf the 

 ruby, with a fa'ir tranfparence, to glaff, is as follows. Cal- 



like oil ; then precipitating with llrong alivaline ley, and 

 v.'afliingthe precipitate v.'ith water, jjy diffolving this pow- 

 der in Ipirit of fait, and precipitating it again, it becomes, he 

 fays, extremely fair ; and in this Hate he directs it to be mij;- 

 ed with a due proportion of Venice glafs. 



Orfchal hi his treatife entitled Sol fine Veile, gives the 



fine ruby. 



cine' in earthen veffels gold dilTolved in aqua regin, the men- follot\-iiig procefs for producing a very fine ruby. He di 

 ftruum being evaporated by dillillation, more aqua regia added, refts the purple prccipiUite, made by tin, to be ground with 

 and the abftraction repeated five or fix times, till it becomes 

 ■ ' will require many dayS in 



a red pou der. This operation wdl require many dayS m a 

 hot furnace ; «hcu the powder is of a proper colour, take 

 it out ; and when it is to be ufed, melt the fiuell cryilal glafs, 

 and purify it, by often calling it into water ; ar.d thcnadd, 

 by fmall quantities, enough of diis red powder to give it 

 jlour of a ruby, with an elegant and perfeft tranf- 



the true col 

 parence. Neri. 



The 

 cf gold 

 century 



See Gem.'*. 



procefs of tinging glafs and enamels by preparations 

 , were f.rft attempte-d about the beginning ot the 17th 



.. I.,ibavius, in one of his trafts, entitled Alehyniia, 



printed in 1606, conieftures that the colour of tlie ruby pro- 

 ceeds from fold, and that gold diffolved, and brought to red- 



fix times Its qiLanti' y of Venice glals into a very line powder, 

 and this compour.d to be very carefully mingled with the frit 

 or vitreous compofition to be tinged. His frit confifts of 

 eOjUal parts of borax, nitre, and fixed alkaline lalt, and four 

 times as much calcined flint as of each of the falts ; but he 

 gives no directions as to the proportion cf the gold precipi- 

 tate, or mode of fufioi;. Hellot delcribes a preparation, 

 which mi::cd with Venice glafs, was found to give a beau- 

 tiful purple enamel. This preparation confiiis of equal 

 parts of iulution of gold, and of folution of zinc in aqua 

 regia, mixed together with the addition of a volatile fait pre- 

 pared from fal ammoniac, in quicklime, in fufficient quantity 

 to precipitate the two metals. The precipitate is then gra- 

 nefs mi^'-ht be made to communicate a like colour to faftitious dually heated, till it acquires a violet colour. However, 

 o-em's and glafs. On this principal Neri, in his '• Art of though a purple or red colour, approaching to that of ruby, 

 Glafs" dated 161 I. gives the procefs above recited. Glau- may, by the ir.ct!;ods above recited, be baked on glafs or 

 ber in 16+8 publilhed a method of producing a red colour enamels, and introduced into the mafs by fufion, tlie way of 

 bv ffold in a matter which is of the vitreous kind, though not equally diffufing fuch a colour through a quantity of fluid 

 perfect o-lafs. For this purpofe he ground powdered Hint or glafs is ftill, fays Dr. Lewis, a fccrct. The following pro- 

 fand wiUi four times its weight of fixed alkaline fdt ; this cefs for making the ruby glafs was communicated to Dr. 

 mixture melts in a moderately llrong fire, and '.vhen cold Lev/is by an artill, wl'.o afcribed it to Kunckel. The gold 

 looks like srlafs, but expofed to the air runs into a liquid is directed to be diffulvcd in a mixture of one part of fpirit 

 ftate. On adding this liquor to folution of gold in aqua regia, of fait, and three of aqua-fertis, and the tin in a mixture of 

 the eold and flint precipitate together in form of a yellow one part of the former of thefe acids with two of tht^ latter, 

 powder, which by calcination becomes purple ; by mix- The folution of gold being properly diluted v.ith water (fee 

 'm<r this powder with three or four times its weight of the Colb preclpilalf, iic.) tlie folution of tin is added, and the 

 alkaline folution of flint, drying the mixture, and melting it mixture left to Hand till the purple matter has fettled to the 

 in a llrom- fire for an hour, a malsisobtained, of a tranfparent bottom. The colourlefs lio^uor is then poured oif, and the 

 rubv colour, and of a vitreous appearance, which neverthe- purple fediment, while moilV and not very thick, is thorouglv 

 lefs'is foluble in vviater, or by the moifture of the air, on ac- ly mixed with powdered f.int or land. This mixture is well 

 count of the redundance of the fait. The honourable Mr. ground with powdered nitre, tartar, bora,-., and arfenic, and 

 Boyle in a work publi(h'.'d in 1680, mentions an experiment, the compound melted with a fuitable fire. The proportions 

 in which a like colour was introduced into glafs without of the ingredients are 1560 parts of fand, 384 of nitre, 240 

 fufion- for, liavinc"- kept a mixture of gold and mercury in of tartar, 240 of bora.x, 28 of arfenic, 5 of tin, and 5 of 

 digeftion for fome'^months, the fire was at lall immoderately gold. Lewis's Com. Phil. Techn. p. 171. 621, &c. 

 increafed fo that the n-lafs burll with a violent exploi'.on ; Gl-As.s, iwhtts-opaque, Rr.i/iwi-tranjpurttit, may be made of 



and the lower part of the glafs was found ting?d tliroughout ten pounds <rf cither of the compofilioas for hard glafs, and 



uiie 



