CHLOR'OPHYLL (Neo-Lat. ehlorophylluni, from Gk. x2erp6c,chloros, greenish-yellow + 2.ov, , iihy(lun, leaf). The green coloring matter of ordinary foliage. This is not a single pigment, but it mixture of at least two, one a green pig ment, to which the name is sometimes restricted, and a yellow pigment, carotin (q.v.) or xantho phyll. Chlorophyll is also often associated with blue (phveocyanin). brown (phycophrein), or red (phycoPryhrin) pigments. especially in the algae showing these tints. Chlorophyll is only found associated with protoplasm, by which, indeed, it is produced. In some of the small plants it may color the whole protoplasm of the cell, but usu ally it is restricted to certain definite portions of the protoplasm called ehloroplasts (q.v.). It is restricted to plants, though it is not found in all, being wanting in the whole class of fungi, and in some of the seed-plants, especially those which live as parasites or saprophytes (q.v.). Chloroplasts have been said to occur in animals, but they turn out on examination to be minute green alga, which live associated with the ani mal (e.g. hydra, sponges, certain radiolaria. etc.). The amount of chlorophyll in leaves, according to Tsehireh, varies from 0.2 to 1 gram per square meter of surface. From the chloroplasts it may be extracted by various solvents, alcohol, ether, fatty and volatile oils, etc., but probably at once undergoes an alteration in Its composi tion. In alcoholic solution it exhibits the prop erty of fluorescence, being emerald-green by trans mitted light and deep blood-red by reflected light. .1Iolis•h's test for chlorophyll is as follows: If a bit of dry tissue to be tested be wetted with a saturated watery solution of potassium hydrate, it instantly turns brown, and after 15-30 minutes becomes again green. This change appears imme diately on heating or adding water.
The chemical nature of chlorophyll is not satis factorily known. It is a complex and exceedingly
unstable nitrogenous carbon compound, probably not containing iron, as once believed. Attempts to analyze it result in so complex a series of de composition products that it is difficult to draw any certain conclusions. All efforts to purify it or to crystallize it meet with the same difficulty, and all the so-Called 'pure chlorophyll' is one or another decomposition product. Chlorophyll is chemically related to haemoglobin, the red color ing matter of the blood, as shown by the fact that phylloporphyrin, a decomposition product of chlorophyll, is very nearly identical with htemato porphyrin, a decomposition product of Memo glohin.
The coloring matters in a live leaf absorb cer tain wave-lengths of light, notably A. 680-660 (between the B and C lines of the spectrum). There are also weaker absorption bands about 7. 015-600, R. 560-540, 2. 530-527 (nearly E line), and extensive absorption beyond A.490. These absorbed portions are utilized in part for the making of food (see ; though the greater portion of the energy is dissipated in evaporating water. In the absence of chlorophyll, however, no formation of carbohydrate foods can occur. To this there arc only unimportant exceptions.
Chlorophyll is formed usually only in the plas tids which lie near the surface of a plant exposed to light of certain intensity. It is produced in darkness in certain exceptional plants. e.g. em bryos of pines. It is only produced within cer tain limits of temperature and in the presence of oxygen. Probably under the normal conditions of life it is being continually formed and as con tinually destroyed. Intense light promotes its destruction, so that plants may become blanched thereby. Ordinary blanching (e.g. of celery) is accomplished by darkening, whereby the forma tion of chlorophyll is checked.