This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Chlorophyll is a suitable agent for coloring liquid perfumes green. Care must be taken to procure an article freely soluble in the menstruum. As found in the market it is prepared (in form of solutions) for use in liquids strongly alcoholic; in water or weak alcohol; and in oils. Aniline greens of various kinds will answer the same purpose, but in a trial of any one of these it must be noted that very small quantities should be used, as their tinctorial power is so great that liquids in which they are incautiously used may stain the handkerchief.
Color imparted by chlorophyll will be found fairly permanent; this term is a relative one, and not too much must be expected. Colors which may suffer but. little change by long exposure to diffused light may fade perceptibly by short exposure to the direct light of the sun.
Chlorophyll may be purchased or it may be prepared as follows: Digest leaves of grass, nettles, spinach, or other green herb in warm water until soft; pour off the water and crush the herb to a pulp. Boil the pulp for a short time with a half per cent solution of caustic soda, and afterwards precipitate the chlorophyll by means of dilute hydrochloric acid; wash the precipitate thoroughly with water, press and dry it, and use as much for the solution as may be necessary. Or a tincture made from grass as follows may be employed:
Lawn grass, cut fine.. 2 ounces
Alcohol............. 16 ounces
Put the grass in a wide-mouthed bottle> and pour the alcohol upon it. After standing a few days, agitating occasionally, pour off the liquid. The tincture may be used with both alcoholic and aqueous preparations.
Among the anilines, spirit soluble malachite green has been recommended. A purple or violet tint may be produced by using tincture of litmus or ammoniated cochineal coloring. The former is made as follows:
Litmus............. 2.5 ounces
Boiling water........ 16 ounces
Alcohol............. 3 ounces
Pour the water upon the litmus, stir well, allow to stand for about an hour, stirring occasionally, filter, and to the filtrate add the alcohol.
The aniline colors "Paris violet" or methyl violet B may be similarly employed. The amount necessary to produce a desired tint must be worked out by experiment. Yellow tints may best be imparted by the use of tincture of turmeric or saffron, fustic, quercitron, etc.
If a perfumed spirit, as, for instance, a mouth wash, is poured into a wine-glassful of water, the oils will separate at once and spread over the surface of the water. This liquid being allowed to stand uncovered, one oil after another will evaporate, according to the degree of its volatility, until at last the least volatile remains behind.
This process sometimes requires weeks, and in order to be able to watch the separate phases of this evaporation correctly, it is necessary to use several glasses and to conduct the mixtures at certain intervals. The glasses must be numbered according to the day when set up, so that they may be readily identified.
If we assume, for example, that a mouth wash is to be examined, we may probably prepare every day for one week a mixture of about 100 grams of water and 10 drops of the respective liquid. Hence, after a lapse of 7 days we will have before us 7 bouquets, of different odor, according to the volatility of the oils contained in them. From these different bouquets the qualitative composition of the liquid may be readily recognized, provided that one is familiar enough with the character of the different oils to be able to tell them by their odors. The predominance of peppermint oil— to continue with the above example— will soon be lost and other oils will rise one after the other, to disappear again after a short time, so that the 7 glasses afford an entire scale of characteristic odors, until at last only the most lasting are perceptible. Thus it is possible with some practice to tell a bouquet pretty accurately in its separate odors.
In this manner interesting results are often reached, and with some perseverance even complicated mixtures can be analyzed and recognized in their distinctiveness. Naturally the difficulty in recognizing each oil is increased in the case of oils whose volatility is approximately the same. But even in this case changes, though not quite so marked, can be determined in the bouquet.
In a quantitative respect this method also furnishes a certain result as far as the comparison of perfumed liquids is concerned.
According to the quantity of the oils present the dim zone on the water is broader or narrower, and although the size of this layer may be changed by the admixture of other substances, one gains an idea regarding the quantity of the oils by mere smelling. It is necessary, of course, to choose glasses with equally large openings and to count out the drops of the essence carefully by means of a dropper.
When it is thought that all the odors have been placed, a test is made by preparing a mixture according to the recipe resulting from the trial.
Not pure oils, always alcoholic dilutions in a certain ratio should be used, in order not to disturb the task by a surplus of the different varieties, since it is easy to add more, but impossible to take away.
It is true this method requires patience, perseverance, and a fine sense of smell. One smelling test should not be considered sufficient, but the glasses should be carried to the nose as often as possible.