45. Green, which, in the general scale of colors and in relation to light and shade, occupies the middle station, is second among the secondary colors. Composed of the extreme primaries, yellow and blue, it is in hue most perfect, constituted in proportions of three of yellow to eight of blue of equal intensities. Such a green will, indeed, perfectly neutralize a perfect red in the proportions of eleven to five, either of space or power.

Of all compound colors, green is the most effective, distinct, and striking. So attractive in its constituents does it appear to the untutored eye, that, when first produced by the mixture of blue and yellow, green impresses the mind with surprise and delight. Mixed with orange, green converts it into the extreme tertiary, citrine. Mixed with purple, it produces the other extreme tertiary, olive. Hence its relations and accordances are more general, and its contrasts with other colors more agreeable, than those of any other. The beautiful verdure that it bestows throughout all nature affords the most welcome repose to the eye, for it emphasizes the beauties in harmonizing with the colors of the flowers for which it forms a background. Greens produced directly of copper, arsenic, etc. are more durable than those composed of blue and yellow.

46. Chrome greens are compound pigments of which chrome yellow is the principal coloring substance. They are also called Brunswick green, etc., which are compounds of chromate of lead with Prussian and other blue colors, beautiful to look upon, suitable, too, for certain mechanical purposes, but unfit for fine art. There is, however, one true chrome, or native green, the coloring matter of which, being the pure oxide of chromium, free from lead, is enduring against the action of sunlight and of impure air. Of various degrees of transparency and opacity, and of several hues more or less warm or cool, it affords pure, natural, and durable tints. True chrome greens neither inflict upon nor receive injury from other pigments, and are eligible for either water or oil painting, in the latter case, drying well as a rule. They likewise afford valuable colors in enamel painting.

47. Brunswick green is one of a large class of pigments, grouped under the name of copper greens, and comprehending verdigris, verdite, malachite, mineral green, Schweinfurt or Vienna green, green bice, Scheele's green, emerald green, green lake, mountain green, African green, French green, marine green, Olympian green, etc., some of which call for special mention.

48. Verdigris, or viride aeris, is of two kinds, common or impure, and crystallized or, more properly, refined verdigris. Both are acetates of copper of bright color, inclining to blue, and are the least permanent of the copper greens, soon fading and becoming white by the action of light, particularly in water colors, and ultimately, through dampness and foul air, turning black.

49. Emerald green is the name of a copper green of an earthy hue. The most vivid of this class of colors being rather opaque and powerfully reflective of light, it appears to be the most durable pigment of its class. Not common in nature, its hue is well suited for brilliant works. The only true emerald green is that of chromium with which nature gives the green color to the emerald. Emerald green is, for purposes of commerce, made of verdigris mixed with a solution of arsenious acid. It is brilliant in color, very poisonous, and difficult to grind.

50. Scheele's green is a compound oxide of copper and arsenic, or arsenite of copper, named after the justly celebrated chemist who discovered it. Of a beautiful, light, warm green color, opaque, permanent in itself and in tint-when mixed with white lead, it is to be cautiously used with Naples yellow, which soon destroys it. Schweinfurt green and Vienna green are the names of pigments similar to that just given. Less affected by damp and impure air, these pigments are, therefore, more eligible than simple copper greens. All these greens are, however, very poisonous.

51. Several other greens are made from copper, such as Brighton green, malachite, mountain green, marine green, Saxon, African, French, patent green, etc. Mineral green is the commercial name of green lakes, prepared from sulphate of copper. It is a good, durable color for house painting, made from bibasic carbonate of copper.