A Practical Treatise on the Manufacture of Perfumery. C. Deite
for instance, oil of turpentine, they show exactly the same behavior as oils free from oxygen; the nitroprusside of copper is not decomposed and retains its gray-green color. If, for instance, oil of cloves is mixed with oil of turpentine, the red coloration by nitroprusside of copper does not appear.
III. Hager's alcohol and sulphuric acid test.—Bring into a test-tube of about 0.5 inch diameter, five to six drops of the oil to be tested and twenty-five to thirty drops of pure concentrated sulphuric acid, and mix the two fluids by shaking, whereby either no heating takes place or a scarcely perceptible one, or the heating is strong or very vigorous and in some cases increased to the evolution of vapors. The mixture is either clear or turbid. After complete cooling, add to the mixture eight to ten cubic centimeters of 90 per cent. alcohol, and after closing the tube with the finger, shake vigorously. The mixture now shows a different color, is clear or turbid, and the deposit formed after standing for one day is also differently colored and either soluble or insoluble in boiling alcohol.
The mixture of oil, sulphuric acid and alcohol is perfectly clear and transparent with oils of bitter almonds, fennel, clove and rose; with anise-seed oil and star anise-seed oil only the alcoholic layer over the mixture of sulphuric acid and oil is clear. The mixture of oil, acid and alcohol is slightly turbid or nearly clear with oils of valerian, peppermint and field thyme. With most of the other volatile oils occurring in commerce, the mixture is more or less milky turbid. Heating of the oil and acid mixtures does not take place with pyrogenous oils (petroleum, benzine) or only to a very slight degree, as with oils of peppermint and mustard.
IV. Hager's guaiacum reaction[3] serves for the detection of oil of turpentine in a volatile oil. By pouring upon as much guaiacum, freshly powdered, as will lie upon the point of a small knife, in a test-tube 1 cubic centimeter (25 drops) of spike oil, and heating nearly to boiling over a petroleum lamp, the oil after being removed from the flame and allowing the undissolved resin to settle, shows a yellow color. By now pouring upon an equal quantity of guaiacum in another test-tube 25 drops of spike oil and 5 drops of rectified oil of t from the flame shows a dark violet color. Various other oils behave in the same manner as spike oil, and hence a content of oil of turpentine can be readily detected in them. Other oils do not exhibit this behavior; but this can be remedied by adding, in testing for oil of turpentine, a few drops of an oil of the first class.
The guaiacum reaction is an ozone reaction and with reference to this, the volatile oils may be divided into three classes:—
a. Oils inclining to the formation of ozone.—Foremost of these is oil of turpentine, especially when rectified. Oils of tansy, rue, mint, juniper, zedoary, etc., show considerably less inclination.
b. Oils which, especially when heated, directly incite the oil of turpentine to form ozone, and to color guaiacum violet or blue.—Such oils are many kinds of oil of citronella, oils of spike, calamus, cedar, etc.
c. Oils with a content of oil of turpentine, which remain indifferent towards guaiacum.—To such oils, if to be tested for oil of turpentine, with the assistance of the guaiacum reaction, a few drops of an oil of the second class have to be added.
V. Hübl's iodine method.—Mr. C. Barenthin has applied Hübl's iodine method for fixed oils to the examination of volatile oils. He uses the following solutions:—
1. Fifty grammes iodine and 60 grammes of mercuric chloride in a liter of alcohol freed from fusel oil, and let stand for 12 hours.
2. Twenty-four grammes of hyposulphite of sodium in a liter of water.
3. A ten per cent. solution of iodide of potassium. Dissolve 0.1 to 0.2 gramme of the volatile oil in 10 cubic centimeters of chloroform, and add first 15 cubic centimeters of the iodine-mercuric chloride solution; let stand three or four hours, and, in case the mixture gets discolored, add a few more centimeters of solution. Now add 10 to 15 cubic centimeters iodide of potassium solution, dilute with 150 cubic centimeters of water, and titrate with hyposulphite till the mixture remains clear for about a minute. The iodide of potassium solution must be added before the water, and the relative proportions between this solution and the iodine-mercuric chloride solution must be 15 to 20 cubic centimeters. The quantity of iodine solution consumed is calculated to iodine for 100 parts and the figure thus obtained is designated as the "iodine number."
Barenthin has in this manner determined the iodine number of several volatile oils; other experimenters, however, for instance, Kremel and Davies,[4] have found different numbers for the same oils, so that this method requires further thorough examination before it can be classed as available.
VI. A. Kremel has endeavored to utilize titration or saponification with alcoholic potash lye for the examination of volatile oils. In his experiments he was guided by the following points: A series of volatile oils contains partially free organic acids, like oils of bitter almonds and cinnamon, and partially aldehydes or other combinations. Now it seems not impossible, that up to a certain limit, the quantities of these combinations in the separate volatile oils remain constant, thus presenting the opportunity of testing the respective oils as to their quality and purity by saponification. In some cases these combinations are the chief bearers of the specific odor, and hence the determination of the "saponification number" becomes of double value. It is, of course, self-evident that not every volatile oil can be saponified, and Kremel admits that, even where saponification takes place, it is not in every case a sure test.
The execution of the method is as follows: Dissolve 1 gramme of the oil to be examined in 2 to 3 cubic centimeters of 90 per cent. alcohol freed from acid, compound the solution with a few drops of phenol-phthalein solution, and titrate the free acid with ½ normal alcoholic potash lye. The milligrammes of caustic potash used are designated the "acid number." After having thus determined the content of acid, add to the same solution 10 cubic centimeters of the same potash lye, heat for ¼ hour upon the water bath, and then titrate back the excess of potash lye with ½ normal hydrochloric acid. In this manner the "saponification number" is obtained. (In some cases when the final reaction is not plainly perceptible, it is advisable to correspondingly dilute with water after heating the alcoholic fluid.) The saponification number, less the acid number, gives the "ether or ester number."
Kremel has in this manner examined a large number of volatile oils and partially obtained surprising results. Rose oil gives a saponification number of 12, and geranium oils one of 40 to 50. While lavender oils give very high saponification numbers, oil of lemons does not. Artificial oil of bitter almonds shows higher saponification numbers than the natural oil. By further compounding the saponified portions of the latter with acid, a crystalline precipitate of benzoin is formed, the quantity of which amounts to from 40 to 50 per cent. of the oil used. Such a precipitate, but only in very small quantities, is also formed in peach kernel oil, but not in other similar oils nor in artificial oil of bitter almonds.
VII. F. R. Williams has recently endeavored to utilize for testing volatile oils Maumené's test, which is based upon the increase in temperature produced in oils by concentrated sulphuric acid, and which gives valuable points for the examination of some fat oils. Of course, the large quantities of oil otherwise prescribed cannot be used. While for the examination of fat oils 50 grammes of oil are mixed with 10 cubic centimeters of concentrated sulphuric acid in a beaker glass wrapped around with cotton, Williams could use only six cubic centimeters of volatile oil. They were brought into a very small beaker glass enveloped in cotton. After reading off the temperature, twelve cubic centimeters of concentrated sulphuric acid were added and the whole stirred with the thermometer until the temperature no longer rose. Numbers were in this manner obtained which might in some cases, for instance, cassia oil, furnish guiding points for judging the purity of the oil.
Planchon proposes the following procedure in order to recognize a volatile oil:—
A. The oil is specifically lighter than water.
1. The substance is solid and only melts at 347° F.: Camphor.
2. The oil at a temperature of over 32° F. contains a crystalline stearoptene.
a. The oil is laevorotatory, the stearoptene melts at 77° F., and, on adding sulphuric acid, a clear solution remains