HELIOCHROMATYPE. Under the article Daguerreotype, notice has been taken of the attempts of Becquerel and Hill, to produce naturally colored impres sions on the silver plate. In March of this year (1851), M. Niepce de St. Victor communicated to the Paris Academy of Sciences, a memoir showing the manner of taking the natural colors. Having formed the idea that there might be some relation between the color that a sub stance communicates to flame, and the color that light produces on a plate of silver chloridized with the substance that colors the flame, he undertook the expe riments which he to his success. He found it necessary to expose the plate to chlorine, and then coat it with the chlo ride of the particular metal he was inves tigating; no other salts acted similarly to the chlorides. Dry chlorine does not produce any effect, but when the plate is immersed in the liquid chlorine, or ex posed to the aqueous vapor, the colors are all reproduced. The mode of operat ing is thus : The bath is made or chlo rine 1 part, and 3 parts of water. When hydrochloric acid, with a salt of copper, is used, it is diluted with 1-10 of water. The liquid chlorine should not be con centrated, as good yellows are. not then obtained. Clear solutions and stoppered bottles should be used. The purest sil ver plate is preferable for these experi ments 2 • this is cleaned with ammonia and tripoli, then plunged into the bath, and left there for some minutes in order to receive a sufficiently heavy the plate is then removed, rinsed with water, and dried by a spirit-lamp. In
the bath it takes on a dark color, almost black, and though it will take the colors, yet the ground will be black. In order to have a clearer ground and a quicker operation, the plate is changed by heat to a cherry red, when the dark plate is heated by a lamp placed below it. It passes through the tints, brownish red, cherry red, bright red, reddish, white, whitish. hi the last stage it has lost the power of producing images. The plate should only be brought to the cherry red condition. It is then to be exposed in the camera. To obtain a picture it requires two hours. This must be owing to IN iepee's not using any accelerator ; he mentions fluoride of soda, chl6ric acid, and the as worthy of trial for this purpose. These images disappear quickly, and Niepee has not been successful in fixing them ; exposing the plate to the flame of alcohol containing chloride of sodium or muriate of ammonia, partially succeeds. The chlorides which, when employed alone, act upon the dyer plate, so as to make it take all the several colors of the model, are the chlorides of copper of iron, of nickel, of potassium, and the hy pochlorites of soda and lime, as well as liquid chlorine.
It is evident from the foregoing, that Heliochromatype is yet but in its infancy, and cannot he practically applied as yet.