It is also used by some for preparing the plate.
Acidulated Solution .-- This solution is used for cleaning the surface of the Daguerreotype plate.

It has the property of softening the silver, and bringing it to a state in which it is very susceptible of being either oxidized or iodized, hence it contributes to increase the sensibility of the plate.

The proportions are to one drop of acid add from 15 to 20 drops of water, or make the solution about like sharp vinegar to the taste.
Nitro-Muriatic Acid .-- Aqua Regia is a compound menstruum invented by the alchemists for dissolving gold.

It is composed of colorless nitric acid (aqua-fortis) and ordinary muriatic acid; the mixture is yellow, and acquires the power of dissolving gold and platinum.

These materials are not properly oxidized; it nearly causes their combination with chlorine, which is in the Muriatic acid.
Hydrochloric Acid (Muriatic Acid) .-- This acid forms a valuable addition to the chemicals employed by the practical Daguerreotypist.