JJ26 Mr. Keales on the Anali/sis of Brass. [May, 



This probably arises from some mechanical combination pf^the 

 two oxides, and not from any chemical union. The following 

 experiment may, I think, be considered as sufticienl proof of the 

 fellacy of the above mode of analysis. 



(A.) ]00 grains of brass dissolved in diluted nitric acid ; the 

 solution vviis heated until it was nearly neutral, and diluted >\'ith 

 distilled water. 



(B.) 540 grains of caustic potash dissolved in six ounces qf 

 water, were added to the solution A in a flask capable of holding 

 36 fluid ounces, using agitation during the mixture. The flask 

 was placed on a sand-bath, and the contents boiled for an hour 

 and a half, precautions being taken to prevent the mixture being 

 tlirown out of the flask, to which it is very liable, from the great 

 weight of the precipitate preventing the regular escape of steam. 

 The whole v/as filtered while hot, and the precipitate, which was 

 of a dark-brown colour, after being well washed, dried,, and 

 heated to redness, weighed 111-5 grains. 



. (C.) The filtered fluid, which was extremely alkaline, was 

 reduced to a convenient bulk by evaporation, and supersaturated 

 with muriatic acid ; carbonate of soda was now added in excess, 

 which threw down carbonate of zinc, this was separated by the 

 filter, and healed to redness ; the oxide of zinc resulting weighed 

 34 grains, equal to 11*2 grains of zinc. 



■I (D.) 100 grains of the precipitate (B) dissolved in dilute siil- 

 phuric acid left a small quantity of sulphate of lead, which, being 

 separated, the solution was rendered very acid, and two polished 

 cylinders of iron immersed in it, which precipitated the copper, 

 this, when collected and dried, weighed rather more than 

 62-5 grains, which gives 70 grains of copper in the 111*5 of 

 precipitate. 



(E.) The solution from which the copper had been precipitated 

 was boiled with nitric acid to peroxidize the iron, and nearly 

 neutralized by carbonate of soda. iYmmonia was now added in 

 excess, and the oxide of iron thrown down by it separated by 

 filtering. 



(F.) The filtered ammoniacal solution was, with the addition 

 of muriatic acid, evaporated to dryness, and the dry mass heated. 

 in a silver crucible to drive ofl' the muriate of ammonia ; after 

 which the residue was dissolved in dilute muriatic acid, to which 

 -solution carbonate of soda was added in excess, and the precipi- 

 tate resulting, after being heated to redness, weighed 22*5 grains, 

 equal to 18 grains of zinc. 

 v/<Thus, then, the pVoducts of the analysis are : 



Copper at D 70-0 



Zinc at C and F . 29-2 



99-2 

 Loss 0-8 



100-0 



