Balsam Copaiba vs. Gurjun Balsam.

By Lyman F. Kebler.

For some time considerable unrest has been displayed by several dealers concerning the questionable purity of some of the balsam copaiba in our markets. On comparing the statistics [From Messrs. Stallman and Fulton.] of importations for the past few years, this anxiety is not without foundation. The arrivals from direct sources of this commodity during 1891 amounted to 205,480 pounds; during 1892, amounted to 185,280 pounds; during 1893, amounted to 80,000 pounds; during 1894, amounted to 82,000 pounds; while the annual sales for consumption are estimated at 122,000 pounds. During the latter part of 1894 about 30,000 pounds of gurjun balsam arrived. At the request of Mr. French, of Smith, Kline & French Company, I have investigated the questionable possibility of detecting gurjun balsam in balsam copaiba by the present methods.

Owing to the natural variable composition of balsam copaiba, its purity cannot always be ascertained with absolute certainty. If the variable composition of balsam copaiba was the only obstacle to surmount, our task would not be so difficult, but when we remember that it is practically impossible to secure this article from first hands (in this country only from third hands) we see how uncertain the genuineness of even a sample becomes from which reliable data can be secured. The tests, until recently, at our command, for detecting gurjun balsam in balsam copaiba, frequently made it impossible for the analyst to render an absolute decision as to its presence or absence when less than 25 per cent. was present.

Balsam copaiba is described as varying in color from a pale yellow to a brownish-yellow, is usually quite transparent, but there are varieties that always remain opalescent. Some kinds are occasionally slightly fluorescent. Samples have come into my hand, guaranteed genuine, and an examination proved them so, that were of a dark amber color and highly fluorescent. Balsam copaiba is insoluble in water, but soluble in absolute alcohol, ether, chloroform, benzine, carbon disulphide and fixed and volatile oils. It varies in specific gravity from 0.940 to 0.993 at 15° C.

In order to obtain the most reliable material possible, samples were obtained from several well-known dealers of this article; some were guaranteed pure, while others were represented to be of questionable purity.

Several samples of gurjun balsam were also secured. The dealers appeared somewhat reluctant to furnish this article, either because they were not in possession of it, or did not desire it to become known that they handled it.

The samples were all examined by the most approved methods, which are briefly reviewed below;

Turpentine.—When a sample of balsam is heated the odor of turpentine should not be emitted.

Fixed Oils.—The residue left after driving off the volatile oil should be transparent, friable and amorphous.

Paraffin Oil can be detected by introducing 1 c.c. of the balsam into a test tube containing 4 c.c. of 95 per cent. alcohol, agitating the mixture well, then suspending the test tube in boiling water until the contents begin to boil; paraffin oil, if present, will separate from the mixture and sink to the bottom, while the balsam is held in solution or in suspension by the alcohol.

Gurjun Balsam.—Hager's test is as follows: To 3 c.c. of a mixture of 1 part of sulphuric acid and 25 parts of pure acetic ether, add 6 drops of the balsam; after a few minutes the mixture will assume a violet hue, if a large per cent. of gurjun balsam is present, and on standing twelve hours it will change to a dark brown or black color.

A second test is as follows: Dissolve 1 drop of the balsam, to be tested, in 20 drops of carbon disulphide; to this mixture add 1 drop of a cooled mixture of equal parts of sulphuric and nitric acids; mix well. If gurjun balsam is present a red or violet tinge will appear.

Glacial Acetic Acid Test, due to Messrs. Dodge and Olcott, is executed thus: Place 1 c.c. of glacial acetic acid (99.5 per cent.) into a test tube; to this add 4 drops of pure, concentrated nitric acid (1.42), mix well; then add to this mixture, carefully, 4 drops of the balsam in question; if gurjun balsam is present, a reddish zone will be formed between the layer of balsam and the acid mixture in a few minutes. On mixing the contents of the test tube well, the whole will assume a reddish or purple color. The degree of color varies with the amount of gurjun balsam present.

Acid Number.—A weighed portion of the balsam is dissolved in alcohol, a few drops of phenolphthalein solution added, and titrated with as eminormal solution of caustic potash. The number of mgms. of potassium hydroxide required to neutralize 1 gramme of the balsam is called the acid number.

The Ammonia Tests.—All varieties of balsam copaiba, except para, when mixed with an equal volume of 10 per cent. ammonia water, will form a clear, transparent solution, more readily when warmed. Again, when 1 part of the balsam is mixed with 10 parts of 10 per cent. ammonia water, the resulting mixture should neither gelatinize nor separate a gelatinous substance, even after standing a day.

The accompanying table contains the results of the examination of the samples secured, as well as a few samples of pure balsam copaiba, adulterated by myself with gurjun balsam.

[1] Equal parts of ammonia water and balsam.
[2] Ten parts ammonia water, and one part of the balsam.
E = ether. C = chloroform. B = Benzine. AA. = absolute alcohol. Ma. = methyl acetate. CS₂ = carbon disulphide. F. and V. = fixed and volatile oils.

The conclusions from the above and other data may be summarized as follows:

(1) The color and the fluorescence or non-fluorescence are of no value.
(2) The wide range of the specific gravity of balsam copaiba makes that factor practically valueless.
(3) The solubility or the insolubility of balsam copaiba are uncertain factors and cannot be relied on. One sample of pure substance is soluble in absolute alcohol, another is not. One sample of benzine will indicate the presence of gurjun balsam, another will not; hence, is valueless as a specific test.
(4) The specific tests for turpentine, fixed oils and paraffin oils are reliable.
(5) The ammonia tests are misleading and are consequently unreliable.
(6) The acid number cannot be relied on. At first the author anticipated valuable results from this source, but was utterly disappointed.
(7) Hager's test is not reliable, especially with less than 25 per cent. of gurjun balsam present.
(8) The carbon disulphide test is fairly reliable with a moderately large per cent. of gurjun balsam. Some varieties of balsam copaiba turn reddish-brown with this test, and it sometimes becomes very difficult to discriminate.
(9) The glacial acetic acid (99.5 per cent.) is perfectly reliable, even when not more than 5 per cent. is present, at least so far as the above results indicate.

The writer has found that gurjun balsam is even more variable im composition than balsam copaiba, consequently an absolute decision is reserved until a thorough test has been made with a fair number of samples. This will be done as soon as sufficient material can be collected.

The U. S. P. instructs us to detect gurjun balsam in balsam copaiba by heating a sample to 130° C, when it will gelatinize if the former is present. Some samples may gelatinize, but a trial proved that the material employed in these experiments increased only slightly in viscosity, not even assuming a semi-gelatinous state. The test is unreliable in toto.

Unless otherwise specified, the dealer will always supply a nonsolidifiable product which will comply with every test in the U. S. P., and yet it is to be used only for mass copaiba. It seems almost absurd to prescribe a series of tests for a substance intended for a special purpose, and yet cautiously omit the test leading to its identification. A balsam copaiba designed especially for mass copaiba should be subjected to the solidification test.

305 Cherry Street,
Philadelphia, Pa.

The American Journal of Pharmacy, Vol. 67, 1895, was edited by Henry Trimble.