Brass . 
85 
Jy be obtained separate from those of the sulphat of cop- 
per. But though this separation takes place to a consi- 
derable degree it is not complete, for at the last the crys- 
tals of each salt are somewhat alloyed with the other, and 
the trouble of picking out the crystals when very small is 
extreme. 
M. Dize^ proposes the following methods. 1. Dis- 
solve the brass in nitric acid, which takes up the copper 
and zinc and leaves any tin with which it is often alloyed. 
Decompose the clear nitrated solution by potash, redis- 
solve the precipitate in sulphuric acid, and add a piece of 
clean bright iron to the solution, previously diluted with 
six times as much water. The copper is by this means 
precipitated in a metallic state, and the solution now 
holds sulphat of iron and sulphat of zinc. Add gallic acid, 
which will slowly separate the iron and leave the zinc. 
Lastly, decompose the sulphat of zinc by a carbonated 
alkali, and estimate the quantity of zinc contained in the 
carbonated oxyd of zinc thus obtained, by proportions 
which will be presently mentioned. The above method 
is useful, but the separation of the iron by the acid of 
galls is excessively tedious. 
2. Dissolve the brass in nitric acid. Dilute with six 
parts of water, and immerse in the solution a cylinder of 
bright clean lead. The copper speedily separates in the 
metallic form round the lead, which last takes its place in 
the solution. As this process advances, the liquor loses 
its blue colour, and when all the copper is separated it is 
slightly yellow. To be certain that no copper remains in 
the solution, add a fresh clean piece of lead and boil for 
some time. The liquor now contains nitrat of lead and 
rntrat of zinc, * Sulphuric acid will now precipitate the 
Jour, de Phvs. tom. 48, 
