CHLOROPHYLL The largest use of oil-soluble chlorophyll is undoubtedly for im- parting a green colour to soaps. For this purpose it has advantages which are unique. It readily blends with the soap to give uniform colouring without "mottling," and the colour is reasonably light-fast. Most import- ant of all, in use it has no tendency to act as a substantive dye on fabrics washed with soap. Attempts to usc much cheaper synthetic dyestuffs as soap colours have generally been un- successful, owing to such dyes• fail- ing to comply with one or all of these requirements. Oil-soluble chloro- phylis intended as soap colours are treated with copper salts to develop the maximum green colour of greatest light-fastness. Normally they contain between 5,000 and 15,000 p.p.m. of copper. The cop- per salt is added at an appropriate stage during the manufacturing process. Naturally, such material is offered in various standard strengths to suit particular purposes. The diluent in chlorophylis for soap colouring is usually a fatty oil such as palm oil or castor oil. For other uses•, such as the colouring of oils, or ointments, other suitable diluents may be used and grades to meet special purposes are available. Whether copper-treated or not, the oil-soluble grades of chlorophyll have similar solubility characteris- tics. When properly prepared they should be completely soluble in fixed oils and fats, in hydrocarbons such as benzene, and in chlorinated hy- drocarbons such as chloroform. The oil-soluble chlorophylIs are not gen- erally satisfactorily soluble in alco- hols. In ethanol or methanol of 90 per cent, v/v strength or over they dissolve in part but the greater part of the actual green colouring matter remains undissolved. In weaker alcohols they are, for practical pur- poses, insoluble. In water they are entirely insoluble. Most essential oils and essential oil isolates readily dis- solve oil-soluble chlorophylis. How- ever, if such coloured oils are then dissolved in alcohol, even strong alcohol, turbid solutions are obtained from which most of the chlorophyll precipitates on s{tanding. Of course, the nature of the diluent, if any, can modify these solubilities somewhat. Hence it is always wise to investi- gate the solubility characteristics of a given chlorophyll sample in order to ensure its sui.tability for the par- ticular purpose in view. WaTER-SOLUBLE CI-ILOROPI-IYLLS. The so-called water-soluble chloro- phylis are, as already mentioned, sodium or potassium salts of chloro- phyllin. In other words, they are not true chlorophylis, but are really chlorophyll derivatives. When they are prepared by hydrolysis of medi- cinal oil-soluble chlorophyll they consist of the sodium or potassium salt of the dibasic acid chlorophyllin (IV), with possibly a proportion of the corresponding salt of the mono- basic acid from which the methyl group has not been split off. If the hydrolysis has been very vigorously conducted they may also contain some of the corresponding salt of the 189

JOURNAL OF THE SOCIETY tribasic acid, isochlorophyllin (V). Further, since commercial oil- soluble medicinal chlorophylis have usually lost part, often the greater part, of their magnesium, water- soluble chlorophylIs l•repared from such materials will also contain a corresponding amount of "mag- nesium-free chlorophyllins" corre- sponding to the mono- and tri-basic acids mentioned above. If, on the other hand, the water- soluble chlorophylis are prepared from copper-treated, oil-soluble chlorophyll, the green component of which is copper phaeophytin, the chlorophyllins obtained are sodium or potassium copper chlorophyllins. They contain copper in place of magnesium. These compounds are intensely blue-green in colour, and are very fast to light--much more m than the oil-soluble, copper- treated chlorophylIs from which they are made. The water-soluble chloro- phylis made from non-copper- treated, oil~so}uble chlorophyll have a dull green to brown colour, the green tint diminishing with the mag- nesium content. Such material is of relatively small value as a colouring agent. Whether or not the water-soluble chlorophylis contain magnesium, are magnesium-free, or contain copper, their solubility characteristics are similar. They dismlve quite readily in water, giving faintly alkaline solutions. If such a solution is acidi- fied, the water-insoluble acidic chlorophyllins are thrown' down as a flocculent precipitate, the super- natant liquid being left practically OF COSMETIC CHEMISTS colourless. Hence the chlorophyllins cannot be used to colour acidic aqueous solutions, but only those ,which are neutral or moderately alk- aline. They will not readily dissolve in strongly alkaline solutions, and tend to be precipitated unchanged from aqueous solution by the addi- tion of too much alkali this is due to a "salting out" effect. However, despite these limitations, the chloro- phyllins, especially those containing copper, are very useful for colouring aqueous solutions. They are also particularly suitable for colouring alcoholic solutions some grades are only soluble in solutions containing up to about 60 per cent v/v. alco- hol, but others will dissolve com- pletely in 90 per cent v/v. alcohol. Such alcoholic solutions, when made strongly acid or alkaline, tend to throw down a precipitate contain- ing some or all of their original green colour. Apart from alcohol, the chlorophyllins are insoluble in most organic solvents, including the hydrocarbons and acetone. The chlorophyllins are insoluble in fixed and essential oils. Those grades which are soluble in strong alcohol can, however, be used to colour alcoholic solutions of essential oils such as perfume formulations. This is worth remembering, especially since the oil-soluble grades, though soluble in essential .oils, are only poorly soluble in alcohol. The water-soluble chlorophyllins are available in various forms and strengths. Liquid or semi-liquid forms usually contain water, in which case they must also contain 190