Chroma

“ Every color can be recognized, named, matched, imitated, and written by its HUE, VALUE, and CHROMA.
(40) The notation used in this system places Hue (expressed by an initial) at the left; Value (expressed by a number) at the right and above a line; and Chroma (also expressed by 26 a number) at the right, below the line. Thus R5/9 means
Hue, value, and chroma unite in every color sensation, but the child cannot grasp them all at once. ”

“ It is a degree rather than a quality, as appears in the expressions, intense heat, light, sound,—intensity of stimulus and reaction. Being a degree of many qualities, it should not be used to describe the quality itself. The word becomes especially unfit when used to describe two very different phases of a color,—as its intense illumination, where the chroma is greatly weakened, and the strongest chroma which is found in a much lower value. “Purity” is also to be avoided in speaking of pigments, for not one of our pigments represents a single pure ray of the spectrum. ”

“ Stains, as they occupy a comparatively limited area in the room color scheme, are of their full chroma value or reduced to three-fourths chroma. In only one instance (18) , Figure 463, do we find a reduction to one-fourth chroma, demanded by the nearly gray color scheme of the walls. We find it to be an established fact that small areas are capable of enrichment by colors of greater purity and higher chroma than larger surfaces. A silver pin may be designed to contain a stone of high brilliancy, but a wall surface has to be materially reduced in chroma to possess color harmony. ”

“ Chrō′mosphere, a layer of incandescent red gas surrounding the sun through which the light of the photosphere passes—also Chrōmat′osphere; Chrō′mo-typog′raphy, typography in colours; Chrō′mo-xy′lograph, a picture printed in colours from wooden blocks; Chrō′mo-xylog′raphy.—Chromatic scale, a scale proceeding by semitones; Chromic acid, an acid of chromium, of an orange-red colour, much used in dyeing and bleaching. [Gr. chrōmatikos—chrōma, colour.]
Chronic, -al, kron′ik, -al, adj. lasting a long time: of a disease, deep seated or long continued, as opposed to acute.—n. ”

“ Examples are constantly found of the mental blur caused by such unfortunate terms, and, since misunderstanding becomes impossible with measured degrees of hue, value, and chroma, it seems only a question of time when they will take the place of tint, tone, shade, purity and intensity. ”

“ The very name leads one to expect something different to the other metals—chroma, colour. The metal is procured from what is known as chrome-ironstone, a combination of protoxide of iron and sesqui-oxide of chromium (FeOCr2O3) . By ignition with potassium we get chromic acid and chromate of potassium, a yellow salt which is used to make the other compounds of chromium. The metal is by no means easy to fuse. ”

“ Visual estimates of color, without the help of any standard for comparison, are continually distorted by doubt, guess-work, and the fatigue of the eye. Hardly two persons can agree in the intelligible description of color. Not only do individuals differ, but the same eye will vary in its estimates from day to day. A frequent assumption that all strong pigments are equal in chroma, is 62 far from the truth, and involves beginners in many mishaps. Thus the strongest blue-green, chromium sesquioxide, is but half the chroma of its red complement, the sulphuret of mercury. ”

“ Previous work with measured scales, made by the tuned crayons and tested by reference to the color sphere, have so trained the color judgment that children may now be trusted with more flexible material. They have memorized the equable degrees of color on the equator of the sphere, and found how lighter colors may balance darker colors, how small areas of stronger chroma may be balanced by larger masses of weaker chroma, and in general gained a disciplined color sense. Definite impressions and clear thinking have taken the place of guess-work and blundering. ”

“ Children have made every example on this plate, with no other material than the five crayons of middle hue, tempered with gray and black. A Color Sphere is always kept in the room for reference, and five color balls to match the five middle hues are placed in the hands of the youngest pupils. Starting with these middle points in the scales of Value and Chroma, they learn to estimate rightly all lighter and darker values, all weaker and stronger chromas, and gradually build up a disciplined judgment of color. ”

“ Chrome yellows are chromates of lead, produced by mixing dilute solutions of acetate or nitrate of lead and bichromate of potash. This makes a medium tint known as middle chrome. The addition of sulphate of lead makes this paler, when it is known as lemon chrome, whereas the addition of caustic lime makes an orange chrome of a darker color. The chromes mix well with oil and with white lead either in oil or water. They stand the sun well, but like other lead salts, become dark in bad air. ”

“ The pigments are white, yellow ochre, chrome yellow light, chrome yellow medium, and chrome yellow dark, burnt and raw sienna, turkey and raw umber, ultramarine and ivory black. The greens are preferably mixed by adding ultramarine to one of the chromes. Shades are formed by the addition of the siennas, umbers, or black. Black and white, mixed to a gray, are useful in reducing the chroma of a hue. The stains should be mixed with hot water and a small amount of glue for a binder. White occasionally comes prepared with glue in its composition. ”

“ Chromatophores.—The chromatophores or plastids are protoplasmic structures, denser than the cytoplasm, and easily distinguishable from it by their colour or greater refractive power. They are spherical, oval, fusiform, or rod-like, and are always found in the cytoplasm, never in the cell-sap. They appear to be permanent organs of the cell, and are transmitted from one cell to another by division. In young cells the chromatophores are small, colourless, highly refractive bodies, principally located around the nucleus. ”

“ Chrōmatop′sia, coloured vision; Chrō′matrope, an arrangement in a magic-lantern by which effects like those of the kaleidoscope are produced; Chrō′matype, Chrō′motype, a photographic process by which a coloured impression of a picture is obtained.—adj. relating to the chromatype.—ns. Chrōme, Chrō′mium, a metal remarkable for the beautiful colours of its compounds.—adj. Chrōm′ic.—ns. Chrō′mite, a mineral consisting of oxide of chromium and iron; Chrō′mo-lith′ograph, or merely Chrō′mo, a lithograph printed in colours ”

“ In Greek music χρωματικὴ μουσική was one of three divisions—diatonic, chromatic and enharmonic—of the tetrachord. Like the Latin color, χρῶμα was often used of ornaments and embellishments, and particularly of the modification of the three genera of the tetrachord. The chromatic, being subject to three such modifications, was regarded as particularly “coloured.” To the Greeks chromatic music was sweet and plaintive. From a supposed resemblance to the notes of the chromatic tetrachord, the term is applied to a succession of notes outside the diatonic scale, and marked by accidentals. ”

“ Is chromate of zinc, a bright pale lemon-like yellow, slightly soluble in water. It is not affected by foul gas, but does not preserve its colour on exposure to light and air, or even when kept in a book. In contact with organic substances it is apt to turn green. Compounded, especially for foliage tints, this yellow is eligible; but if purity of hue be desired, it should certainly not be employed alone. In this chromate, as in many others, the affinity of the chromic acid to the base is small ”

“ Christophany, kris-tof′a-ni, n. an appearance of Christ to men. [Gr. Christos, and phainein, to appear.]
Chromatic, krō-mat′ik, adj. relating to colours: coloured: (mus.) relating to notes in a melodic progression, which are raised or lowered by accidentals, without changing the key of the passage, and also to chords in which such notes occur.—ns. Chrōm′ate, a salt of chromic acid; Chrōmat′ics, the science of colours.—v.t. Chrō′matise, to impregnate with a chromate.—ns. Chrōmatog′raphy, a treatise on colours; Chrōmatol′ogy, the science of colours, or a treatise thereon ”

“ CROCOITE, a mineral consisting of lead chromate, PbCrO4, and crystallizing in the monoclinic system. It is sometimes used as a paint, being identical in composition with the artificial product chrome-yellow; it is the only chromate of any importance found in nature. ”

“ A dark green pigment prepared from oxide of chromium; mixed with Prussian blue and chrome yellow it is called Green Cinnabar.
Chrome Ochre. Oxide of chromium of a fine yellowish green.
Chrome Red. A chromate of lead; a durable pigment used in oil painting. (See Red Lead.)
Chrome Yellow. A chromate of lead, which makes a bad pigment for oil painting. It is very poisonous and not durable; when mixed with white lead it turns to a dirty grey. As a water-colour pigment it is less objectionable. ”

“ From this standpoint these cells are true chromatophores. In an eye exposed to the light the pigment-granules occupy distal positions in these cells; in one in the dark they come to lie in proximal positions. The place occupied by the pigment in a given eye is entirely determined by the presence or absence of light in that eye, for the two eyes have no sympathetic relations. Moreover if a persistent shadow is cast on part of one eye, the condition characteristic for the dark is assumed by that part even though the pigment in the rest of the eye is in the position characteristic for light. ”

“ Ordinary light passes through transparent bodies without producing any very striking effects in its passage; but this extraordinary beam of light has the power of insinuating itself between the molecules of bodies, and by illuminating them, and giving them every variety of prismatic hue, of enabling the eye to detect something of the structure of the mass. The chromatic phenomena of polarized light are so striking, that no description can convey an adequate idea of their character. ”

“ This indicates the presence of a substance or substances that take stain more readily than the mass of the protoplasm. This peculiarity led to the naming of the deeply staining portion of the protoplasm chromatin, referring to the ease of staining. The part of the cell which contains chromatin is called the nucleus. In many kinds of cells the nucleus can be made out by an expert observer without resorting to stains, although the details of structure cannot be seen in that way. ”

“ Many of the chromacea live in hot springs, with a temperature of fifty to eighty degrees centigrade, in which no other organism is found. Other species may remain for a long time frozen in ice, and resume their vital activity as soon as it thaws. Many chromacea may be completely dried up, and then resume their life if put in water after several years. ”

“ A third method of producing a chromatic passage—this time, however, with the left hand, without any assistance from the bow for the division of the notes—seems to be a speciality of Servais. It is introduced both in slow portamento effects and rapid chromatic passages. ”

“ Such instances as the independent retinal chromatophores of Palæmonetes and the nervously dependent chromatophores of Chameleon and Anolis lead me to believe that chromatophores are effectors evolved independently of nervous control, but in some cases secondarily appropriated as nervous end-organs.
What has been said of chromatophores so far as their relation to nerves is concerned is probably also true of glands. The majority of glands are unquestionably independent of direct nervous control. ”

“ Chrome is mined in Asia Minor, Greece, Canada, New Caledonia and California. Its salts are prepared in chemical laboratories.
Chromite (oxide of chromium and iron) is the only ore.
Bichromate of potash is the most important compound. It, together with chromic acid, is used in tanning soft leather. A small percentage added to steel makes it very hard and suitable for burglar-proof safes, tools, etc. Salts of chrome are used for dyes and pigments, such as chrome yellow, chrome green, etc.
Coal is one of the most important of all rocks and first among fuels. ”

“ I am at present engaged on the theory of the achromatic object-glass, with regard to spherical chromatism — a subject upon which, I believe, nearly all our text-books are silent, but one nevertheless of vital importance to the optician. I can only proceed very slowly with it, on account of having to grind and figure lenses for every step of the theory, to keep myself in the right track; as mere theorizing is apt to lead one very much astray, unless it be checked by constant experiment. ”

“ In films which are properly stained with Wright's fluid the young organisms are small, round, ring-like or irregular, sky-blue bodies, each with a very small, sharply defined, reddish-purple chromatin mass. Many structures—deposits of stain, dirt, blood-plaques lying upon red cells, etc.—may simulate them, but should not deceive one who looks carefully for both the blue cytoplasm and the reddish-purple chromatin. ”

“ The glands contain coloring matter, and the changes of color in the frog's skin are due to the distribution of these pigment-cells, and the power they have of shrinking or contracting under nerve irritation. The pigment varies in individuals and in different parts of the body. Brown, black, yellow, green, and red are the colors most frequently observed. The color-cells are technically known as chromatophores. If the web of a frog's foot be placed on the stage of a microscope and examined with an achromatic lens, the chromatophores can readily be made out. ”