BRA 



if 50 grains of pure copper are dilTolved in nitric aciJ to 

 fxccfs, and then precipilated by metallic lead, of which 

 about 220 grains are requifite, the cupreous precipitate 

 weiglis I 3S grains inllead of the original 50 grains, and 

 therefore is not pure copper, but an alloy of this metal, 

 with a very lar^^e proportion of lead. This method, there- 

 fore, of analyfing brafs n hijjhly erroneous, unlcfs the fup- 

 pofcd copper precipitate be feparatcly treated, in order to 

 free it from the large proportion of lead with which it mull 

 be alloyed. 



The following methoJs are given by Vauqnelin : 



3. DilTolve a given quantity of brafs in nitric acid, p\it 

 it in a well-clofed bottle, and add cnuilic pop-ath to excefs, 

 To that there fliall be a fenfible alkaline talte in the liquor ; 

 (hake the mixture well, and keep it a -fliort time in dig-ef- 

 lion. By this fnn[ne procefs the oxyd of copper is preci- 

 pitated by the alkali, but the oxyd of zinc is re-dilTolved in 

 k ; and if the liquor be now tiltcnd, the alkaline iolution 

 of zinc pafFes through clear, and the oxyd of copper is left 

 behind. This oxyd is brown, and nearly metallic in ap- 

 pearance. When thorou;^'hly wafhed, and gently dried, it 

 contains rtj per cent, of metallic copper. It one is afTurtd 

 by a previous affay, that the brafs only contained copper and 

 zinc, when the quantity of copper is thus obtained, th.at of 

 the zinc may be inferred from the ditTerence between the 

 copper, and the weight of the brafs employed ; or elfe the 

 alkaline folution of zinc may be fuperi:ituratcd with ful- 

 phuric acid, fo as at firft to precipitate, and afterwards to 

 rc-diflblve the zinc, after which this metal may be precipi- 

 tated as a carbonat, by adding carbonat of pot-afh or foda. 

 A very trifling quantity of copper paffas into the alkaline 

 folution of the zinc, occafioned by a fmall portion of am- 

 monia formed by the nitrated metals when the cauftic alkali 

 is added, which takes up this atom of copper. If necef- 

 fary, the copper might be again precipitated by heating the 

 alkaline folution, fo as to expel the ammoniac ; but not to 

 boiling, otherwife fome of the zinc would feparate from the 

 alkali, and caufe a greater error. 



4. Diffolve brafs in fulphuric acid, dilute with 20 times 

 as much water, and immei fe a Itick of zinc exactly weighed. 

 The copper foon precipitates completely in the metallic 

 ftate, which is to be well wafr.ed and weighed. The folu- 

 tion now contains only the zinc of the brafs, and the zinc 

 diflblved out of the ftick of metal immerfed. By weighing 

 the undilTolved ftick of zinc, and precipitating the whole 

 by carbonat of pot-a(h or fcda, an cafy calculation will give 

 the portion of zinc belonging to the brafs : or, more fimply, 

 this may be inferred from the copper obtained, and the 

 quantity of brafs originally employed. 



It only remains, on the fubjedl of analyfis, to give the 

 metallic contents of carbonat of zinc. Dize diflblved 100 

 parts of zinc in nitric acid, precipitated it by carbonated foda, 

 and this produdt, well wafhed and dried, now weighed 180 

 parts. Hence 100 parts of carbonat of zinc thus obtained, 

 contain 55.5 of metalliczinc. 



On the other hand, Vauquelin found that carbonat of 

 zinc obtained from the fulphat by carbonated pot-a(h, well 

 •wafhed and calcined in a crucible to expel all the carbonic 

 acid, contained 69 per cent, of metallic zinc. Hence the 

 carbonat obtained by Dize, it is obvious, muft only have 

 been dried at a low temperature, probably that of boiling 

 water ; and from either of the above data the quantity of 

 zinc msy be eftimated : or elfe the carbonat or oxyd may 

 be mixed with charcoal, and ftrongly heated in an earthen 

 retort, without the accefs of external air, by which the zinc 

 will be reduced, and will diftil over, and condenfe in the 

 «aol neck of the retort in the metallic ftate. 



BRA 



Analyfis fliews a vaft variety in the proportions of the 

 different fpecies of brafs ufed in commerce ; nor is it eafy 

 to determine whether the perfeAion of this alloy depends 

 on any certain proportion of the two metals, or the mode 

 of manufafture. In general, the extremes of the highell 

 and loweft proportion of zinc are from 12 to 25 parts in the 

 hundred. Even with fo great a quantity of zinc as 23 per 

 cent., the dudility of brafs is not injured, provided it be 

 manufaftured with care, though zinc itftlf is fcarcely mal- 

 leable. In proof of this, Dize analyzed a fpecimen of a 

 remarkably line brafs, which is made at Geneva forefcape- 

 ment wheels, and otlrer nicer parts of watch-making. This 

 metal unites great beauty of colour to a high degree of 

 duSility ; and the bars that are perfed; fetch a very high 

 price with the watch-makers of this town, fo celebrated for 

 this delicate manufadlure. This brafs was found to conliil 

 of y^ of copper, and 25 of zinc. Probably, too, the copper 

 was Swedifli, or of iomc other very fuperior kind. The 

 common brafs of Paris appears to contain no more thau 

 about 13 per cent, of zinc. The Englilh, probably, con- 

 tains more /.inc. 



The ufe of brafs is of very confiderable antiquity ; but 

 from the inacnracy of the ancient defcriptions, and their 

 ignorance of the tine nature of zinc and its ores, much un- 

 certainty prevails on this fubjedt. Moll of the genuine 

 relics of antiquity of this kind are compofed of various mix- 

 tures of brals, with tin and other metals, and are rather to 

 be termed bronzes. Por this and the other yellow alloys of 

 copper, fee Copper. 



Keir, in a note to the article brafs in Macquer's dic- 

 tionary ; Watfon's EfTays ; Sage in J. Phyf. vol. xxxviiii. ; 

 Dize in ditto, vol. xlviii. ; Repertory, vol. xiv. ; Vauquelin 

 in An. Ch. vol. xxviii. ; Encycl. Melh. ; Original, S:c» . 



Brass, in Antiquily. See jEs. 



Brass, in a more extenlive fenfe, includes copper, and 

 all the mixtures or allovs of Cf>ppcr with other minerals. In 

 which fenfe, brafs amounts nearly to the fame with the Ro- 

 man x.%, and the French ahain. 



huASs-Zumps, or Brasses, in Mineralogy, a conwion nam* 

 among the colliers for the maffes of pyrites that are found, 

 to accompany, more or Icfs, the different kinds of coal. 



Brass d'Or, in Geography. See Cape Breton. 



Brass, St. Bay of, lies eall by north from cape d'Aguillas, 

 on the eall fide of the cape of Good Hope. S. lat. 34°. 



IE) A AS s i/Jciti J, one of the fmallcr Virgin illands, iituate near 

 the N. W. end of St. Thomas's ifland, on which it is dcr- 

 pendent. 



Brass town, a town of America, in the flate of TenefTee, 

 fituate on the head waters of Hiwaffee river, about 100 miles, 

 fouth from Knoxville. Two milei S. from this town is the 

 " Enchanted mountain." 



Brass -wire. See Wire. 



BRASS.Jl. See Bressay. 



BRA8SAC, a town of France, in the department of Puy 

 de Dome, and chief place of a canton in the dillritl of" 

 Iflbire, feated on the AUier ; 3 leagues S, of IlToire. 



Brassac (le Belfourtas, a town of France, in the de-- 

 partment of the Tarn, and chief place of a canton in the 

 dillria of Caftres ; 4 leagues E. of Callres. The town 

 contains 1149, and the canton 4190, inhabitants ; the terri- 

 tory includes 195 kiliometres and 5 communes. 



BRASSAU. See Cronstadt. 



BRASSAVOLA, Antonio-Musa, in B'wgrnphy, pro- 

 feffor in medicine and philofophy at Ferrara in Italy, who 

 flourifhed in the early part of the 16th century, was a dili- 

 gent invefligator into the properties of medicines, both fimple 

 and compounded. Hs was educated luider Manardi and 



X.eonicini, 



