B8 
Brass* 
ly weighed. The copper soon completely precipitates in 
the metallic form, and requires only to be well washed 
and weighed. The solution now contains only the zinc 
of the brassy together with the zinc lost from the piece 
immersed to precipitate the copper. By weighing the 
remainder of the stick of zinc, and precipitating the whofe 
by carbonated potash or soda, an easy calculation will de- 
termine how much of the oxyd of zinc is derived from the 
zinc contained at first in the brass. Or, more simply* 
this may be inferred from the copper obtained, and the 
quantity of brass originally employed. 
It remains on the subject of analysis to give the con- 
stituent parts of carbonat of zinc. Mi Dize dissolved 
100 parts of zinc in nitric acid, precipitated it by carbonat- 
ed soda, and this product well washed and dried now 
weighed 180 parts. Hence 100 parts of carbonat of zinc 
thus prepared would indicate 55.5 of metallic zinc. 
On the other hand Vauquelin found that carbonat of 
zinc obtained from the sulphat by carbonated potash* 
well washed* and calcined in a crucible to expel all the 
carbonic acid, contained 69 per cent, of metallic zinc. 
Hence the carbonat obtained by Dize must have been 
dried at a low temperature, probably that of boiling wa- 
ter, and from either of the above data the proportion of 
zinc may be estimated i or else the carbonated oxyd 
may be mixed with about a fourth of charcoal and strong- 
ly heated in an earthen retort with the beak dipping in 
water, by which the zinc will be reduced and will rise in- 
to the neck of the retort* or partly fall into the water be- 
yond. 
Analysis shews a vast variety in the proportions of the 
different species of brass used in commerce. In general 
the extremes of the highest and lowest proportions of zinc 
are from 12 to 25 per cent, of the brass. Even with so 
much as 25 per cent, of zinc, brass, if well manufactured*. 
