1053 



CHLOROPAL. 



CHLOKOPHYLE. 



1051 



CHLOROPAL is a Mineral of a greenish-yellow or pistachio-green 

 colour. It is a Silicate of Iron. 



CHLOROPH.<EITE, a Mineral found by Dr. Macculloch in the 

 Isle of Rum. It occus in small masses imbedded in basalt or a black 

 indurated ironstone. Its colour when fresh broken is green, which 

 becomes black by exposure to the air. It is brittle and soft enough 

 to be scratched with a quill. Its specific gravity is 2 - 02. Some 

 specimens are transparent, others are opaque. The lustre is vitreous ; 

 the fracture of the transparent sort is conchoidal, of the opaque inter- 

 mediate as to conchoidal and granular. (Phillips's Mineralogy.) 



CHLOROPHANE. [FLUOR-1 



CHLOROPHYLE. (Endochrome, Pkytocldore, Ckromule.) The 

 green colouring-matter of plants. It is obtained by bruising, press- 

 ing, and then washing leaves with water, and afterwards treating them 

 with alcohol, which dissolves the green colour and wax ; when water 

 is added to this solution, and the alcohol distilled, the green substance, 

 which contains wax, floats on the surface of the water ; when this is 

 heated with ether, the wax is dissolved, and Chlorophyle remains 

 nearly pure. When exposed to light, or the action of chlorine, it is 

 bleached. Acids produce a similar effect, and by the alkalis it is con- 

 verted into soap. The red tint which leaves assume in autumn appears 

 to be owing to the formation and action of an acid ; the green colour 

 is restored by an alkali. 



This substance has been recently investigated with great care by 

 Mulder, and the following account of it is chiefly derived from his 

 researches as given in his ' Chemistry of Animal and Vegetable 

 Physiology.' : 



It is a striking fact that young leaves have a much lighter green 

 colour than those which are older, showing that the quantity of 

 Chlorophyle increases with the age of the leaves. If Chlorophyle were 

 a substance poor in oxygen, and were derived from substances rich in 

 oxygen, this fact alone would be sufficient to explain the power which 

 the green parts possess of separating oxygen. This however is not 

 the case : Chlorophyle is rich in oxygen. Nevertheless the leaves give 

 off oxygen not because they are green, but whilst they are becoming 

 green. 



When green leaves are digested with ether the liquid becomes 

 green. On evaporating the etherial solution, and treating the residue 

 with hot alcohol, a considerable amount of white fatty matter (wax) 

 separates on cooling, while the green colouring-matter remains in 

 solution. Before proceeding to the consideration of the green 

 colouring-matter, it will be expedient to say a few words respecting 

 the mixture it forms with the wax. 



In a physiological or botanical sense this mixture has the name of 

 Chlorophyle ; in a chemical sense the term is restricted to the actual 

 green pigment. To prevent confusion, the former is designated as 

 B. Chlorophyle, and the latter as C. Chlorophyle ; B. indicating the 

 botanical, and C. the chemical signification of the word. 



We find similar mixtures of a waxy fat and colouring-matter in 

 other external parts besides the leaves, namely, in the skins of fruits, 

 especially of such as are coloured ; and on digesting them in ether 

 we obtain a large quantity of waxy matter in solution, varying in tint 

 according to the colour of the skin ; being gray when obtained from 

 apples, and of a beautiful orange-colour when obtained from the berries 

 of the Mountain-Ash. 



The degree in which the action of light contributes to the change 

 of colour in the C. Chlorophyle which exists in the perisperms, and 

 to the production from it of the colouring-matter of the skin of ripe 

 fruits, may be obviously inferred from the green colour which such 

 fruits retain if they do not receive a sufficient supply of solar light, 

 or from the difference of colour exliibited by the opposite side of the 

 same fniit, as well as from the fact that leaves when deprived of the 

 action of light become colourless, while if completely exposed to its 

 action they secrete a considerable amount of B. Chlorophyle. 



This apparently anomalous difference in the action of light on the 

 skins of fruits and on leaves is dependent on the same cause as the 

 change of colour in the leaves during autumn ; namely, that light can 

 only produce B. Chlorophyle when there is a sufficient supply of 

 materials for its renewed formation as often as the existing quantity 

 is decomposed by the influence of the light ; and that as soon as this 

 supply is exhausted the green colouring-matter is itself decomposed, 

 and other compounds are formed from it. 



Light acts powerfully in keeping plants green, and likewise exerts 

 a powerful decomposing action upon all colouring-matters, the C. 

 Chlorophyle not excepted ; thus asparagus, potatoes, young leaves, 

 Ac., become green whenever they are exposed to light, and hence 

 there must be a substance widely diffused through plants, which 

 causes the production of Chlorophyle. The change takes place not 

 merely on the surface, but beneath it as far as light can penetrate 

 through the semi-transparent parts. All plants however are not 

 coloured green ; some have no colour at all, while others are speckled 

 or spotted, or of a colour entirely different from green. Hence we 

 conclude that in these plants or parts of plants, the materials yielding 

 Chlorophyle are absent. We may sometimes observe in summer one 

 single spot of a green leaf coloured red by the action of insects or by 

 being injured by hail ; the green colouring-matter is at the spot decom- 

 l>Mrti-d bv the light ; no new portion is formed, and the spot acquires 

 the same colour which the whole leaf would have assumed in autumn. 



From this we infer that the change of colour in the leaves during 

 autumn is simply dependent on a chemical alteration of the green 

 colouring-matter by light. 



Mulder, after showing from a large number of facts that wax along 

 with a green colouring-matter exists in leaves and unripe fruits, 

 wax, with a red colouring-matter, in the red leaves which appear in 

 autumn, and in the red fruits, and wax with a yellow colouring- 

 matter, in the yellow leaves of autumn, and in the yellow fruits gives 

 a lengthened chemical description of Chlorophyle, for an account of 

 which we must refer to the original work. 



From Mulder's experiments, and those previously instituted by 

 Berzelius, it appears that the green colouring-matter of the leaves is 

 readily decomposed into three different substances, one yellow, another 

 blue, and a third black ; and that according to the proportion of these 

 three mixed with the green, a different kind of green must be produced. 

 Hence the difference in the green colour of different leaves depends 

 not only on the presence of more or less Chlorophyle, but also on the 

 different mutual proportions of these three colouring-matters. 



The quantity of pure C. Chlorophyle contained in the leaves is 

 exceedingly small ; according to Berzelius it is not more than the 

 amount of pigment in dyed cotton. 



If a tincture of pure Chlorophyle be exposed to the action of the 

 sun the green colour becomes in a few hours converted into a yellow. 

 When a solution of pure Chlorophyle in ether and hydrochloric acid 

 was kept for five months in a bottle half full, the green was entirely 

 changed into a yellow. From these experiments we learn, first, that 

 the green colouring-matter is decomposed and a yellow one left, both 

 with and independently of the influence of light ; and secondly, that 

 in all probability a similar decomposition (accompanied by a repro- 

 duction) of green colouring-matter and green leaves is constantly 

 going on under the influence of light. Mulder conceives that the 

 continual decomposition of the green colouring-matter may be in part 

 the origin of the wax, since the quantity of the latter is found to have 

 increased when the same leaves are analysed later in summer. In 

 consequence of the continuance of this reproduction, the leaves remain 

 green ; when it stops, the leaves become yellow as in autumn. 



It is worthy of notice that decomposed Chlorophyle yields a blue 

 colouring-matter ; it is this which is no doubt present in the skins of 

 many fruits, as for instance those of the grape ; the exact nature of 

 the chemical change is not clearly understood. 



It is very obvious that the influence of light will convert starch 

 into Chlorophyle. Every part of an amylaceous root becomes green 

 on exposure to light. The parts of plants which become green (all 

 without exception) contain starch ; nnd in autumn as this green 

 colour decreases the starch also decreases, and finally cannot be 

 detected by the iodine-test. Hence starch ceases to form B. Chloro- 

 phyle under the influence of light, the B. Chlorophyle being a complex 

 substance consisting chiefly of wax. The change of starch into 

 B. Chlorophyle may be explained in much the same manner as its 

 conversion into fat. 



The wax contained in the leaves and other parts of plants may be 

 chemically represented by the formula C 15 H 13 0. Now if no other 

 products be simultaneously produced we may suppose the wax 

 obtained from the starch in the following manner : 



6 equiv. of starch .... C uo H, 0,,, 

 With 10 of water .... H 10 0,J 



Make C^H^O,,, 



And 4 of wax C.,, H..., O. 



Leaving to be given off . . . 5B 



That is to say, 5 equivalents of starch yield 4 equivalents of wax, and 

 give off 56 equivalents of oxygen. This fully explains the phenomenon 

 why plants, while becoming green, evolve oxygen, and further indicates 

 the use of starch in the leaves. 



Mulder has, as far as we are aware, made only one \iltimate analysis 

 of pure C. Chlorophyle that from poplar leaves; from this analysis 

 he calculated the formula C,, H B N O e . 



"Properly speaking," Mulder observes, " the green colouring-matter 

 in the leaves has nothing to do with the evolution of oxygen ; on the 

 contrary, the colourless C. Chlorophyle, which seems to be every 

 where present, becomes green by the absorption of oxygen. Hence a 

 small portion of the oxygen produced from the conversion of starch 

 into wax is employed for this purpose, and is not mixed with the 

 atmosphere. But this is just the reason why C. Chlorophyle is not 

 formed by the exhalation of oxygen ; it only becomes green instead 

 of white, as it previously was. This can only happen when there is 

 an abundance of oxygen, and this we have seen to be the case when 

 starch is converted into wax. We may therefore assume as proved 

 that white Chlorophyle diffused throughout the whole plant, will 

 become green in proportion as starch is converted into wax ; because 

 it is enabled, in such proportion, to take up oxygen to become 

 oxidised, just like white indigo. 



"Now, the probable composition of green Chlorophyle, C,, H 8 

 N 0, shows that pure white Chlorophyle is not produced from starch. 

 It is necessary that an axotised body in a liquid state shoiild penetrate 

 into the globule of starch, which during tins transformation into wax 

 ia converted into C,, H a N O 8 . We do not know yet what that 



