announced
by M. Neipce, and his experiments have proved highly successful.

The following is submitted as worthy of trial:

"The proper preparation of the chloridated plate, to enable it to
receive colored impressions is an object of the first importance to
those wishing to experiment on it, and consequently requires particular
notice. The plate may be prepared by making it the positive pole of a
battery, and letting it at the same time be immersed in chlorine water.
The negative pole should be a slip of platinum. All the colors may be
produced from a plate so prepared if the chlorine and water are in the
right proportions; but generally one color or the other predominates,
according to the amount of chlorine in the liquid. By adding the
chlorides of strontian, uranium, potassium, sodium, iron, or copper to
the liquid, various effects may be produced, and these bodies will be
found to produce the same color on the plate that their flame gives to
alcohol.

"The honor of this discovery is due to M. Neipce. Copper gives a
variegated flame; hence many colors may be impressed on a plate
prepared with a solution of its chloride.

"M. Neipce recommends a solution of the mixed chlorides of copper and
iron, and it is with these, that I have been most successful. As the
chlorides of copper and iron are not much used in the arts, they are
not generally found for sale in the shops; and it may be well to
furnish those not much versed in chemistry with an easy method of
preparing them.

"They may be made directly from either metal by dissolving it in
hydrochloric acid; but they may be formed by a cheaper method, and by
which also the acid fumes are avoided.

"Sulphate of iron or copper, or both together, may be dissolved in
water and then neutralized with common crude potash, or its carbonate
or bicarbonate--known commonly as pearl ash and saleratus. If either
of the latter be used, there will be formed sulphate of potash and a
carbonate of the metal used, and there will also be a considerable
effervescence of carbonic acid, which will, if care is not taken, cause
the mixture to run over the vessel. After the copper or iron salt is
neutralized, which is known by its ceasing to effervesce, the carbonate
of the metal will settle slowly, and will at first nearly fill the
vessel. The supernatant fluid, which is sulphate of potash in
solution, may now be carefully poured off, and its place filled with
water; this operation