NOTES ON THE ANALYTICAL EXAMINATION OF TINCTURES. BY ALFRED H. ALLEN, F.C.S. Read before the Society of Public Analysts, 01% 30th &d, 1879. I HAVE had occasion lately to make some experiments on the L 6 Tinctures ” of the British Pharmrccopceia, and as Borne of my experiences are of a rather novel character they appear worth recording. spirits ” of pharmacy, are of two distinct alcoholic strengths.‘‘ Rectified Spirit, B.P.” ( ~ p . gr. 0838 = 84 per cent. by weight of absolute alcohol = 1554 per cent. of proof spirit), is directed to be employed iu the preparation of the tinctures and spirits of chloroform, ether, aconite, ferric chloride, ferric acetate, iodine, myrrh, nux vomica, camphor, ginger, &c. On the other hand, “Proof Spirit, B.P.” (sp. gr. *920 = 49 per cent.by weight of absolute alcohol), is directed to be used in making the tinctures of orange-peel, belladonna, cantharides, crttechu, digitalis, ergot, opium, rhubarb, squills, &c. In many instances, the alcohol is the chief element of cost in the preparation of tinctures, and there is consequently a Btroug inducement to economise it as much as possible. Hence, it is not unusual to find proof spirit substituted for rectified spirit, and a mixture of equal measures of rectified spirit and water for proof spirit.Of course, alcohol so deficient in strength is apt not to dissolve the sctivc oonstituenta of the drugs employed. I may premise that the so-called tinctures ” or102 THE ANALYST. On the other hand, some of the leading h e prepare their tinctures with alcohol of 60° O.P., and yet use it in the same proportion as if it were merely 5 5 O O.P., as required by the Phermacopaia.In many of the official tinctures, the determination of the alcohol presents no mculty. Mere distillation will’suffice to separate it in a state of approximate purity from the tinctures of aconite, arnica, belladonna, calumbs, capsicum, catechu, jalap, nux vomica, opium, quinia, &c.; and the same is true of the tinctures of iodine, ferric acetate, &c., if they be first rendered distinctly alkaline with caustic soda. On the other hand, the tinctures of benzoin, myrrh, ginger, camphor, rhubarb, &c., give a distillate contaminated with essentid oils or similar volatile matters in quantity sufficient to affect, more or less seriously, the determination of alcohol by the density.The same is true of the d 6 aromatic spirit of ammonia,’’ and tinctures prepared with it, With the additional objection that the distillate will contain ammonia, unless the rtlkacline reaction of the spirit be previously carefully neutralized by hydrochloric aoid. If any of the tinctures to which the distillation process is not directly applicable be diluted considerably with water, the essential oil is precipitated more or less completely, but usually in so fine a state of division that filtration is compIetely useless.I find, however, that this difficulty may be got over very simply by operating in the following manner :-50 C.C. of the sample are taken and diluted with water to about 350 C.C.This causes the precipitation of the greater part of the essential oil or resinous matter. A few drops of a strong solution of calcium chloride are next added, and this is followed by some solution of sodium phosphate, the liquid being vigorously stirred. The flocculent precipitate of calcium phosphate effectually entangles the finely divided essential oil and clarifies the liquid.The liquid is next diluted to a definite volume, 400 C.C. being sufficient if the tincture were prepared with proof spirit, but 500 is preferable if rectified spirit should have been originally employed. The solution is then thoroughly agitated and passed through a dry filter. A known measure is then carefully distilled at 8 low temperature, and the distillate made up exactly to the volume occupied by the liquid before distillation. The density of the distilled spirit is then taken, and the corresponding percentage of proof spirit learnt by reference to a table.Evidently the proportion of proof spirit in the original tincture will be either 8 or 10 times the amount found in the distillate, according to the extent of dilution practised.It is convenient to state the strength of the tincture in percentages of proof spirit, as any deficiency in strength is then at once apparent, and the extent of dilution is readily calculated. With a view of testing the accuracy of this mode of assaying tinctures, I have made various experiments, The following; data, indicate the extent to whioh the process may be relied on, A sample of thcture of myrrh ww prepared according to the directions of the Phamruoopcleia, ma on examination gave the following results :- 8p.Uravity = Proof spirit = Absolute Ahohol by volume. by weight. Spirit used for prepsring tincture.. . . . . . . -8378 166.7 841 Tincture.. . . . . . . . . . . , . . . . . . . . . . . . . . . . 146.0 77.3 16087 80.8 Bpirit in tinoture odoulated from results *8649 I 181.0 80.9 of distillationTHE ANALYST.103 It would appear from these results, that about 6 per cent. less of proof spirit was obtrtined than was present ~JI the dcohol used in prepaxing the tincture, and, therefore, that the method is in error to this extent. This conclusion is not justified, for in the above calculation it is tuisumed that no increase in the bulk of the spirit occurs on saturating it with myrrh; but the following data show that this assumption is not warranted :-5 grammes of myrrh previously dried at looo C.were added to 40 C.C. of rectified spirit of *a280 specific gravity. After standing 48 hours, the tincture waB filtered, the residue washed with a little spirit, dried, and weighed. Its weight was 3.142 grammes, so that 1.858 grammes had dissolved in the spirit.The density of the tincture was found to be -8432. The weight of alcohol used was 0828 x 40 = 33.120 grammes, which, added to the weight of the dissolved myrrh, gives 34-978 as the weight of the tincture. This, divided by the observed density, gives 41.4 c.c., as the measure of the tincture. Hence 100 C.C. would have increased to 103-5 C.C.In another experiment the volume was found to be 103 c.c., and in a third experiment, on double quantities, it came to 104*6. The mean of these estimations is 10387, Thus the percentage of alcoholfound in tincture of myrrh ought to be multiplied by 1.037 to get the true strength of that employed in its preparation. Applying this correction to the alcohol found by distillation of the tincture of myrrh, we obtain 156-3 and 156.6 per cent.of proof spir8, against 156.7 employed in preparing the tincture, a result which leaves nothing to be desired. A very striking example of expansion of the fluid occurs in the preparation of the ‘6 Spirit of Camphor, B.P.” In one experiment I pIaced 10 grammes of camphor in a graduated cylinder, and added 90 C.C.of rectified spirit of 0830 specific gravity, The tincture produced measured exactly 100 c.c., so that, as camphor has a density of 0996, 10 grammes would measure 9.96 c.c., and hence camphor dissolves in alcohol without sensible change of volume. The tincture was found by experiment to have a density of -8446, the theoretical density, assuming no change of volume, being 08466.Therefore the action of alcohol on camphor appears not to be strictly that of a solvent. It seems to act rather by causing liquefaction of the camphor, subsequently mixing with the resultant liquid without notable change of volume. Its action may be compared to that of chloral hydrate on camphor. In consequence of this peculiarity, the proportion by volume of proof spirit oontained in spirit of camphor will be ianths of that present in the alcohol used in its preparation, and there is no doubt that a similar correction ought to be applied in certain other cases.When the modified distillation process already described is applied to spirit of camphor, the determination of the alcohol can only be affected approximately. Even when the spirit is previously diluted with 9 times its volume of water, the distillate has a distinct smell and taste of camphor.This is doubtless a consequence of the solubility of camphor in water, for the distillate obtainelt from tincture of myrrh retains no trace of its. origin. It is very probable that Monell’s colorimetric method* might be advantageously utilized for the estimation of alcohol in spirit of camphor, but I have not been able to try the experiment.* Journ., Chem. Soc,, 1878, II., 246. .104 THE ANALYST. I have not made any attempt to determine the camphor in a spirit or tincture containing it, but may suggest that its action on polarized light would probably afford a fairly accurate means of estimating it. The specific rotatory power of common or dextro-camphor, in alcoholic r3olution, is + 47.4 for the transition tint.My attention has been recently called to the analysis of the offioial ‘‘ Compound Tincture of Camphor,” owing to the following circumstances. A medicd practitioner in Sheffield had reason to aupect some compound tincture of camphor supplied him by R well-known local pharmacist, and so submitted it to a wholesale firm in London, whose ohemist reported it to be deficient in alcohol anit some other constituents.The medical man thereupon, through the agency of n brother practitioner, called the attention of the inspector to the matter and supplied him with a signed written order (in Latin) for 8 oz. of the fiincture, In due course, the sample was procured and stlbmitted to me, and I certified that it contained only about 54 per cent.of absolute alcohol (=71*4 per. cent. of proof spirit), instead of being made with proof spirit, and was nearly destitute of benzoic acid itnd oil of anise. The proportion of opium was not found to be deficient, and I expressed 110 opinion on the proportion of camphor. In the sequel, the vendor was prosecuted and fined $5 and costs. From a consideration of the facts, it seems probable that the proportion of alcohol was cut down from motives of economy.The deficiency of alcohol oompels a considerable reduction in the proportion of the oil of anise, as the weaker spirit used will not dissolve the half-drachm to the pint prescribed by the Pharmacopceia. In devising a method for examining such a complex preparation as the compound tincture of camphor, it appeared desirable to analyse a number of samples of known purity. In this I have been assisted by Mr.L. Siebold, of Manchester, to whom I am indebted for the analytical results obtained by the examination of three samplw of the tinoture, and for a check-analysis of the adulterated sample. In the following description, A and B are specimens of the tincture purcharred br Mr. Siebold in Manchester, and probably prepared with spirit at 600 O.P.C ie a sample prepared by Mr. Siebold himself. C 1 S and C 1 A are the adulterated sample as examined by Mr. Siebold and myself respectively; and C 2, C 3, C 4, and C 5 we samples purchased from well-known Sheffield pharmacists ; C 5 being prepared specially for me. The following are the densities of the original samples, without distillation or my other manipulation :- A B C C 1 S C 1 A C 2 C S C 4 C6; -9147 *9150 *9206; *9608 09633 09231 *9321 *9212 09240 From these figures it is evident that the small proportions of solid constituents present in compound tincture of camphor do not very materially affect the density, and hence that the specific gravity dords a very good approximate indication of the strength of the alcohol with which it was prepared.However, the modified distillation process already described admits of the deter- mination of the alcohol with all desirable accuracy, provided that a slight exeess of alkali be added prior to distillation to prevent volatilization af Irenmic wid. By * The quantity of tincture at Mr. Siebold’s disposal ww very small, and the density wa8 determined by nowg the weight of 10 0.0.THE ANALYST.105 proceeding in this manner, the alcohol is obtained unmixed with anything except the 19 grains per ounce of camphor, an amount which I have proved experimentally has no appreciable influence on the density. The clarification of the liquid with chloride of aalcium and phosphate of sodium is really superfluous in the case of the compound tincture of camphor, for the small proportion of the oil of anise does not affect the densi€y of the distillate, though it renders it milky.A useful modification of the process is to employ chloride of calcium, but to precipitate it with carbonate of sodium instead of the phosphate, aid thus clarify the diluted tincture and render it dkaline at the same time.The experiments made on the samples of compound tincture of camphor already mentioned have shown that the true percentage of proof spirit, as determined by distillation, is never more than two degrees in excess of that deduced from the density of the original tincture. The alkaline liquid which remains in the retort after distilling off the spirit is of service for the determination of the benzoic acid. If concentrated to one-half of the volume of the original tincture employed, it should give an immediate and copious precipitate of benzoic acid on being strongly acidified by concentrated hydrochloric acid.If the acid liquid be then shaken with ether, and the upper layer of liquid removed with w pipette, the benzoic acid is readily obtained in a state of approximate purity.If the etherial layer be transferred to a small beaker, and the ether evaporated spontaneously by a current of dry air from an aspirator or bellows, the benzoic acid remains as a crystahe r e d u e , which may be further examined. If the shaking with ether be repeated the extraction of the benzoic acid is perfect, a very fair approximate determination of its quantity may be obtained, even on as small a quantity as 6 C.C.of the tincture. Chloroform may be substituted for the ether with some little advantage. In the adulterated sample, neither Mr. Siebold nor I could detect any traoe of benzoio acid; the etherial extract was but faintly acid, a re-action which proved to be due to the presence of a trace of meconic acid.A very fair idea of the proportion of opium present in compound tincture of camphor may be obtained by diluting the sample with proof spirit and adding ferric chloride. By comparing the depth of red colour produced with that given by a standard tinuture, in a manner similar to Eggertz’ colorimetric method of determining carbon in steel, a good approximation to the proportion of opium can be obtained.Of course the percentage of meconic acid contained in different samples of opium is somewhat variable, snd hence the determination is but approximate. A useful check is obtained by drying up a known measure of the tincture until the residue ceases to lose weight ; but such a process is quite invalid if the tincture has been artificially cohred by caramel or similar material, a practice which is extremely common, I have recently examined several ssmples of ‘( Paregoric Elixir ” which were found to be wholly destitute of opium.As the name “Paregoric Elixir” was formerly official, and has never been applied to any other preparation than that now represented by the compound tincture of camphor, this omission appears to be a distinct infringement of the Sale of Food and Drugs Act.* a Since this paper was read, two convictions have taken place at Dewsbury for selling k k Paregorio Elixir ” which W ~ S destitute of opium.106 THE ANALYST.The proportion of oil of anise present in a sample of compound tincture of camphor may be judged of by the readiness with which the liquid is precipitated on dilution with water. With a, proper proportion of oil, hardly any dilution can be dected without a milky precipitate being formed. In the case of the adulterated sample already described no precipitation occurred, no matter how much water WRS added. It was also proved by experiment that the proportion of oil of anise which could be dissolved in spirit of 30° 0.P. was but a mere fraction of that taken up by proof spirit. Mr. Siebold found that samples A, B and C were precipitated by water even when mixed with seven volumes of proof sph-it, and from this fact he estimated the proportion of oil of anise in C 1 S at less than one-eighth of the normal amount. In addition to assistance afforded me by Mr. 8iebold, I have to acknowledge my indebtedness to Mr. W, F. Cocker, mho has made most of the test experiments in trial of the processes described in this paper.