BRASS

Syn. Æs , Æ′′ris metal′lum , L.; Airain , Laiton , Cuivre jaune , Fr.; Erz , Me ing , Ger.; Bræs , Sax. A well-known alloy of copper and zinc. Prep. Bra is now generally manufactured by plunging copper, in slips, into zinc melted in the usual manner. The former metal rapidly combines with the fluid ma , and the addition is continued until an alloy somewhat difficult of fusion is formed, when the remainder of the copper is at once added. The bra thus obtained is broken into pieces, and remelted under charcoal, and a proper addition of either zinc or copper made, to bring it up to the colour and quality desired. It is next poured into moulds of granite. Before being submitted to the rolling-pre for reduction to thin plates it undergoes the operation of annealing. The proportions of the metals forming this alloy are varied according to the desired colour, and the purposes to which it is to be applied. The following formulæ are founded chiefly on analyses of standard bra es and yellow metals, made expre ly for this work. Small fractions are omitted; the nearest whole numbers being generally taken:— a. Fine Bra :—1. Copper, 2 parts; zinc, 1 part; either combined, as explained above, or the two metals separately melted, suddenly poured together, and united by vigorous stirring. 2. Copper, 7 parts; zinc, 3 parts. Bright yellow; malleable. 3. Fine copper, 4 parts; zinc, 1 part. Deeper coloured than the last; an excellent and very useful alloy. b. Malleable Bra :—1. Copper, 33 parts; zinc, 25 parts; as before. 2. Copper, 3 parts; zinc, 2 parts. These alloys are malleable whilst hot. c. Red Bra . This name is commonly applied to all those alloys which do not contain more than 18 to 20% of zinc. In the deeper-coloured foreign varieties ( RED TOM′BAC ) the per-centage of copper occasionally amounts to 88, 90, or even 92%. d. Yellow Bra . See Fine Bra ( above ). e. Button-bra :—1. Copper, 8 parts; zinc, 5 parts. This is the ‘ PLATIN ’ of the Birmingham makers. 2. Yellow bra , 16 parts; zinc, 2 parts; tin, 1 part. Paler than the last. 3. Copper, 25 parts; zinc, 20 parts; lead, 3 parts; tin, 2 parts. Pale; used for common buttons. f. For fine Castings :—1. As fine bra , according to the colour desired. (See above .) 2. Copper, 62 parts; zinc, 35 parts; lead, 2 parts; tin, 1 part. 3. Copper, 60 parts; zinc, 36 parts; tin, 4 parts. Both the last two are rather pale and brittle. 4. Copper, 90 parts; zinc, 7 parts; tin, 2 parts; lead, 1 part. Rich deep colour. 5. Copper, 91 parts; zinc, 5 parts; tin, 3 parts; lead, 1 part; as the last. g. For Gilding :—1. As fine bra ( above ). 2. Copper, 64 parts; zinc, 32 parts; lead, 3 parts; tin, 1 part. 3. Copper, 82 parts; zinc, 18 parts; tin, 3 parts; lead, 1 part. h. For Solder :—1. Fine bra , 12 parts; zinc, 6 parts; tin, 1 part; melted together. 2. Bra , 2 parts; zinc, 1 part; as before. 3. Bra , 3 parts; zinc, 1 part. Very strong. Used for soldering tubes and other like purposes requiring great strength. The above alloys form the ‘ HARD SOLDER ’ of the braziers. For certain purposes a little silver is added to them, when the compound receives the name of ‘ SILVER-SOLDER ,’ i. For Turning :—1. Fine bra , 98 parts; lead, 2 parts; melted together. 2. Copper, 61 parts; zinc, 36 parts; lead, 3 parts. 3. Copper, 65 parts; zinc, 33 parts; lead, 2 parts. j. For Wire :—1. Copper, 72 parts; zinc, 28 parts; the resulting alloy being subsequently properly annealed. 2. Copper, 64 parts; zinc, 34 parts; as before. 3. To the last add of lead, 2 parts. Anal. This may be briefly described as follows:— a. 100 gr. of the alloy is digested in nitric acid. The insoluble portion is peroxide of tin, every 74 gr. of which, when washed and dried, contain 58 gr. of metallic tin. b. Sulphuric acid is added to the nitric solution as long as a white precipitate falls; after a time the precipitate is collected on a filter, washed with a mixture of water and alcohol, and ignited in a porcelain crucible. Every 152 gr. of the residuum represents 104 gr. of metallic lead. c. The liquid filtered from the precipitate of sulphate of lead is treated with a stream of sulphuretted hydrogen; the precipitate is collected on a filter, washed with water mixed with a little sulphuretted hydrogen, dried, and digested in pure nitric acid until the sulphur which separates acquires its natural full yellow colour; the resulting solution is next diluted with water, and rep rec i pita ted with pota a, the whole being boiled until the precipitated oxide of copper becomes of a deep brown or black; it is then collected on a filter, washed, dried, ignited in a platinum crucible, and weighed therein immediately after it becomes cold. Every 40 gr. of oxide of copper thus obtained represents 32 gr. of pure copper. d. The liquid poured from the precipitate of sulphide of copper is boiled for about a minute, when it is precipitated with a solution of carbonate of sodium; the whole is then boiled for a few minutes, and the precipitated oxide of zinc collected, washed, dried, and ignited. Every 40 gr. of this oxide contains 32 gr. of metallic zinc. Concluding Remarks. In the adoption of his formula the operator should be entirely led by the object he has in view. The larger the proportion of copper, the deeper will be the colour, and the greater the density, and, within certain limits, the toughne of the alloy. Zinc le ens the specific gravity and colour. Tin gives it hardne and grain; whilst lead toughens it, and renders it fitter for turning. These facts are known to every experienced bra -founder. See Alloys , Copper , Mosaic Gold , Prince’s Metal , Tombac , .