Part 3

=Green.=—_Auramin_ (very dilute) washed with _light green_. (The auramin should be applied first, because it "sets" or becomes fast quickly, while the light green does not, but is largely removed by overwashes of the yellow, thus rendering it very difficult to get the desired hue.)

=Hues between green and blue.=—_Methyl green_; the same washed with _light blue_ (Diamond Dye); for the hues nearer blue, _light blue_ washed with Winsor and Newton's _permanent blue_ or _new blue_ (the least violet-hued of the artificial ultramarines).

=Blue.=—_Light blue_ washed with _permanent blue_ or _new blue_. (Although the color is nearer that of the artificial ultramarines named, it is useless to apply the latter first, for overwashes of the light blue merely sink through and darken the color without improving the hue. A moderately saturated solution of the light blue should be applied first, and when this is dry covered with one or more rather thin washes of the permanent blue or new blue).

=Hues between blue and violet.=—Winsor and Newton's _permanent blue_ and some of the more violet-hued artificial ultramarines, the hues nearer violet washed with _crystal violet_ or _gentian violet_.

=Violet.=—_Crystal violet._

=Hues between violet and red.=—_Methyl violet 1b._ washed with _rhodamin b._; for hues nearer red, _rhodamin b._ with Devoe's _geranium red_ (dry) or _crocein scarlet b._

While more or less similar in hue to rhodamin b., several other aniline dyes, as _acid fuchsin_, _rubin s._, _rosein_, _magenta_, etc., do not combine satisfactorily with the violets, the mixture soon becoming dark or dull and none of them are quite as pure a purple or red-violet.

It is most important to remember that disks thus colored must be carefully protected from light when not in actual use and _never_ exposed to direct sunlight. The artificial ultramarines are, of course, permanent, and so, practically, are crocein scarlet, gold orange, orange g., and auramin—that is to say, are not materially affected by the action of light except after very prolonged exposure, though the last named undergoes a change of hue; but the green and violet aniline dyes are all very evanescent, rapidly fading and eventually disappearing; light blue and rhodamin, while sensitive to light, are far less so than the greens and violets.

ALPHABETICAL LIST OF COLORS REPRESENTED ON PLATES OF THIS WORK