2699. Cremnitz White

2699.      Cremnitz White, a beautiful white, with less body than ordinary white lead; it is, doubtless, made by precipitation ; it, like ordinary white lead, decomposes sulphides, and is decomposed by sulphuretted hydrogen.

2700. Cadmium Yellow, Bed, etc

2700.     Cadmium Yellow, Bed, etc. These are sulphides of cadmium, and, when well prepared, are very stable; they can be used in fresco and silicious painting. It is mentioned elsewhere that cadmium sulphide decomposes emerald green. (See No. 2712 (Emerald Green).) It is not safe to use it with lead pigments, unless it has been most carefully prepared; and here, inasmuch as decomposition may take place, and lead sulphide, which is black, be formed, it is better to avoid the mixture; no such mixture can occur in fresco or silicious painting, and it would be well if there were no chance of its occurring in any other style of painting, by the banishment of white lead from the Est of artists' pigments. No other salts of cadmium are important as pigments.

2701. Green Oxide of Chromium

2701.      Green Oxide of Chromium. This oxide is perfectly stable, and, as so many tints of it can be obtained, including the beautiful vividian, it can be used in all vehicles, and is perfectly permanent in fresco and silicious painting. Other chromium compounds are used in painting; the chromates of lead have already been treated of. Chromate of barytes is a good, safe pigment; it is used under the name of lemon yellow. It is permanent in fresco and silicious painting. The chromates generally are unstable colors, and, as there are so many other good yellows, they should not be used as pigments.

2702. The Ochres are earths colored by oxide of iron

2702.    The Ochres are earths colored by oxide of iron. The natural color of these earths is yellow, but by burning they get darker, and some become red. Indian red, red ochre, light red, etc., are all earths with more or less of the oxide of iron in them. All the ochres are permanent and stable if they have been well prepared. They may be used safely in every style of painting.

2703. Colcothar

2703.    Colcothar is also an oxide of iron ; it is very permanent, and generally useful as a pigment. It can be obtained of different tints. It is, however, especially useful in fresco and silicious painting.

2704. Venetian Bed

2704.    Venetian Bed, as now prepared, is an iron red; but, whether from adulteration or not, it contains lime; and, as it is made from the sulphate of iron, sulphate of lime gets formed, and this prevents its employment in silicious painting, for with silicate of potash a silicate of lime is immediately formed, and it becomes hard and lumpy. It may be used in oil, water, and fresco.

2705. Chrome Yellow

2705.    Chrome Yellow. To a solution of bichromate of potash add a solution of nitrate of lead as long as a precipitate forms. Wash the precipitate, and dry it with a gentle heat. An inferior kind is said to be made by 4 pounds pure white lead, 1 pound bichromate of potash, and 20 pounds water, and boiling till the water becomes colorless. Or 75 parts of precipitated sulphate of lead may be acted on by 25 parts of a hot solution of neutral chromate of potash. A mixed product of chromate and sulphate of lead is thus obtained, which is said to cover as well as the pure chrome, and is much cheaper. (Riot.)