| Bichloride of Mercury | 30 | grains. |
| Distilled Water | 1 | fluid ounce. |
By a gentle application of heat the corrosive sublimate dissolves and forms a solution as nearly as possible saturated at common temperatures. The addition of a portion of Muriatic Acid enables the water to take up a larger quantity of Bichloride; but this concentrated solution, at the same time that it whitens more quickly than the other, is apt to act unequally upon different parts of the image.
Before applying the Bichloride, the image is to be fixed and the plate well washed. Either the Protosulphate of Iron or the Pyrogallic Acid with Acetic ([p. 223]) may be used for the development; but the whitening process is more rapid and uniform in the latter case.
SECTION II.
Formulæ, etc., for Negative Solutions.[34]
[34] The same Collodion and Nitrate Bath may be used both for Positives and Negatives if required; but there are a few minor points of difference which are included in the following remarks.
THE COLLODION.
FORMULA No. 1.
| Purified Ether, sp. gr. ·720 | 5 | fluid drachms. |
| Purified Alcohol, sp. gr. ·825 | 3 | fluid drachms. |
| Soluble Pyroxyline | 4 to 8 | grains. |
| Pure Iodide of Cadmium or Ammonium | 4 to 5 | grains. |