24 Color Standards and Nomenclature. 
or broken. The difficulty is increased by the additional 
fact that any black pigment mixed with almost any color 
falls short of even the color-wheel mixture in purity of 
hue in the resulting shades, owing to the very consider¬ 
able amount of gray in all black pigments. Chromo¬ 
lithography can be made to produce clearer and better 
shades of the pure colors, but is distinctly objectionable 
for the purpose of a work of this kind owing to eventual 
oxidation of the oil or varnish with which the pigments 
are combined in lithographic inks, causing a change of 
hue; reds becoming more orange, blues more greenish, 
etc., in course of time. 
While the absence (in large part) of pure chromatic 
shades is much to be regretted, the defect is not so seri¬ 
ous, from the standpoint of utility , as might appear at 
first sight; for while saturated or darkened pure colors 
are not uncommon in the animal, vegetable, and mineral 
kingdoms, more or less broken dark colors are infinitely 
more so; and since the latter are greatly increased in 
number by the defect mentioned the actual result is 
rather an advantage than otherwise. 
It will doubtless be noticed that there is a conspicu¬ 
ous difference in relative darkness between shades of 
yellow and contiguous hues on the one hand and corre¬ 
sponding ones of violet and adjacent hues on the other, 
as if the percentage of black in each were very different. 
This, however, is entirely the result of difference of 
luminosity of the two sets of colors, that of yellow being 
between 7000 and 8000 while that of violet is only about 
13;* for the percentage of black in corresponding tones 
of the vertical scales is precisely the same for each color 
throughout the chromatic scale of this work. 
*See Rood, Modern Chromatics, pages 34, 35. 
