532 Intelligence and Miscellaneous Articles, 
almost invariably require to be touched up afterwards, and therefore 
absolute identity is destroyed. The cost of their manufacture would 
be trifling, being merely the value of the zinc*^ dissolved in the bat- 
tery, and a pound of zinc of the value of sixpence would produce a 
copper-plate weighing about two pounds ; and I trust that copper 
will again, from its beauty, take the place of steel engravings. 
So much for the precipitation of the copper ; and the next thing 
to which I have to direct your attention, is a mode of making a copper- 
plate engraving without an engraving in the first instance. This is 
done by drawing upon a smooth piece of copper (such as a plate 
used for engraving) with any thick varnish or pigment insoluble 
in water, and then exposing the plate in the usual way to the in- 
fluence of the current, when first copper will be thrown down upon 
the uncovered parts and will gradually grow over the drawing, and 
the electrotype when removed will be ready for printing. A practical 
difficulty, however, arises in the application of this in the arts, for un- 
less very thick oil paint is used, sufficient depth is not obtained to hold 
the ink. However, judging from the sharpness of the edges of the lines, 
I have but little doubt that this difficulty may be overcome by those 
who are accustomed to drawing ; and it possesses, as an additional 
advantage to its cheapness, the valuable property of not requiring 
the artist to reverse the design. An opposite effect to this may be 
produced by placing a piece of copper similarly drawn upon at the 
oxygen end of the battery, when the metal will be acted upon, lea- 
ving a drawing in basso relievo. 
Bank of England, April 21, 1840. 
ON THE REDUCTION OF CHROMATE OF LEAD. BY R. F. MAR- 
CHAND. 
The employment of chromate of lead, instead of oxide of copper, 
in organic analysis, is in many cases recommended by Richardson. 
It is preferable in the examination of substances containing chlorine, 
iodine, bromine, and sulphur, but particularly in the examination of 
the two latter. Erdman and I have frequently employed it with 
Hess’s apparatus, and observed that the reduced chromate of lead 
will again absorb oxygen and might be then again employed. This 
circumstance induced me to make various experiments upon the 
reduction of this salt. 
The chromate of lead used in these experiments was prepared by 
the precipitation of a solution of nitrate of lead with an excess of 
bichromate of potash, and afterwards carefully washing it : the salt 
was heated to dryness ; it became of a dark red colour approaching 
cinnabar red ; on cooling it returned to its former yellow colour 
provided it was not fused. If fused it turned to a dark brown co- 
lour, which on reducing to powder was of a brownish yellow colour. 
When the fused salt is quickly cooled by throwing it into cold water 
it becomes of a permanent red colour, giving also a red powder. 
* The zinc in the fluid might be precipitated as a carbonate, for which 
there is great demand in the arts, and thereby the expense of the electro- 
type would be furtlier diminished. 
