run into a tared beaker, evaporated and dried at 110°C. to constant weight. The residue was thus treated for nine consecutive times, with the following results: No. 1. Amount of resin dissolved 5. : Amount of resin dissolved This series of experiments shows that, at least with dry ether, the solvent action does not go on indefinitely, as it certainly does when alcoholic ether is employed, and this fact is a strong point in favour of the employment of a dry ether in the ether solubility limit if this test is to be of any practical value what ever. Another series of experiments was made to find out whether there is any real difference in the solubility of a jalap resin in ethers of different strengths, (a) in the anhydrous state, and (b) in the ordinary condition as found in stock containing the usual amount of moisture. One Gm. of anhydrous resin and the same quantity of a resin containing 4.5 per cent. of moisture were treated separately and consecutively with 40 mils of 0.720, 0·730, 0-735 ethers respectively, and gave the following results : This shows that at least this amount (4.5 per cent.) of moisture has no retarding influence upon the solubility of the resin so long as dry ethers are employed as the solvents and in all probability this amount of moisture is completely absorbed by the dry ethers, so that no retardation of solubility takes effect until a weak ether is employed. Unfortunately time would not permit further work in this direction, but it is a point well worth investigating, as in all probability by using resins with gradually increasing percentages of moisture a point would be reached which even dry ethers would lose in solvent action, hence the necessity of always working with anhydrous resin. The acid value indicates the number of milligrammes of potassium hydroxide required to neutralize the free acids in 1 Gm. of resin. It is therefore merely a measure of the free acids in the resin, and it is of considerable importance in the valuation of a resin, as it acts as a check on the manufacturer's method of purification, and also upon any acid resins which might inadvertently or otherwise become incorporated with the genuine article. In carrying out this part of the work it was particularly noticeable that the acid values of the pure resins were uniformly 2-8, corresponding to 0.1 mil, N/2 KOH, and from this fact-that the amount of acidity was found to be so constant in the pure resins—it was considered to be in all probability natural acidity, and 0·1 mil N/2 KOH per Gm. was therefore carried over to the saponification equivalent, but all higher amounts were deducted as being due to want of purification or the presence of foreign acid resins. In the case of the brown resins, which are much less pure than the white, the acid values are all much higher, one requiring as much as 0.5 mil N/2 KOH per Gm. of resin (limit of acidity in the U.S.P.) and the other 0.4 mil; in these cases 0.4 and 0.3 were respectively allowed for in order to obtain a fair saponification equivalent, as the excess of free acids would in all probability be due to acid substances, which would be removed in the further purification of the resin. The U.S.P. acid limit of 0.5 mil N/2 KOH is not required for white resins, but it is too low for brown resins. I would suggest for white resins an acid value limit of 8.4 and for brown an acid value limit of 20. The figures for the acid values and saponification equivalents are the means of four determinations each, and it will give some idea of the concordance of these results when it is stated that in the majority of these individual figures are identical with the mean. This is merely pointed out to emphasize the fact that with ordinary care very concordant results are easily attainable, and this is due in a great measure to the fact that the blank is carried out under precisely the same conditions as the actual experiment, so that by using prepared reagents from the same stock for a series of operations the unavoidable alcoholic impurities and carbon dioxide use up the same amount of alkali in each operation, and the results are thereby brought with very fine limits. This is one of the points at which the U.S.P. so manifestly falls short of the logical mark in an otherwise excellently initiated method, giving as it does a method for determining the limit of saponifiable substances without sufficient details to make it sufficiently accurate for the purpose intended. The saponification equivalent is the number of grammes of resin saponified by the equivalent of potassium hydroxide in grammes; that is, by 56.1 Gm. KOH, or by one litre of a normal solution of any caustic alkali. The detailed particulars have already been given for obtaining the figure, and it only remains for me to discuss the variation in the saponification equivalents of the different jalap resins. It will have been noticed that pure jalapin gave a saponification equivalent of 408, whilst two samples of pure white jalap resin gave 417 and other two samples of brown jalap resin gave respectively 333 and 338. These figures will at first glance appear to be paradoxical, but on closer examination it will be seen that they are correct. The pure jalapin is the highest standard of a jalap resin, and the standard figure is 408. The question then arises, Why do the samples of white jalap give a higher saponification equivalent than the jalapin? The answer is because the impurity in the white jalap resin increases the saponification equivalent figure for the same amount of alkali required; that is, 56-1 KOH. Again, it might be asked, why do the samples of brown jalap resin give a lower figure than the standard? The answer is because the chief impurity in these samples is scammonin, which possesses a much lower saponification than jalap resin, hence the lowering of the figure. The respective tests for colophony, guaiacum, aloes, and starch gave no indication of any of those substances, but all these tests should be given in an authoritative work such as the B.P. SO as to afford means of detecting the more early-added adulterants, as well as the natural impurities. The physical constants of jalapin and white jalap resin were determined with the following results: These figures indicate that pure white jalap resin as found commercially, after removal of moisture and ash, is, for all practical purposes, jalapin. Before the relative values of these resins can be judged they require to be placed in two distinct classes: (a) White jalap resins (almost free from scammonin). (b) Brown jalap resins containing varying amounts of scammonin). The relative values of the white resins may approximately be arrived at in terms of percentage purity by employing the following formula, which is based upon the fact that the purest obtainable jalapin has the approximate saponification equivalent of 240: Relative Value = 408 × 100 Sapon. equivalent of resin of which percentage purity is required For example, a white jalap resin has a saponification equivalent of 420, the approximate percentage purity would therefore be: The relative values of the brown resins cannot be judged in such a simple manner on account of the greater number of impurities, and I intend to continue my investigations further in this direction. The PRESIDENT felt sure that all present were indebted to Mr. Cowie for bringing the subject forward in this manner, and for working it out so thoroughly. The matter might not seem to be one of supreme importance at first sight, but everything connected with the valuation of medicinal substances was of importance, and it was very desirable that they should know exactly how to test products like these. He thought they should be very careful not to fix too high a standard for natural products, which should not be treated as though they were pure chemical substances. In jalap resins there were many things which he should be disposed to look for even in products which might have been prepared in the proper way. For instance, he should certainly look for sugar in jalap resin, as he had even found 6 per cent. of sugar in aconite root. If they wanted a pure product let them have it by the use of proper methods of preparation, but if they wanted the natural product the test should not be too rigid. Mr. W. A. H. NAYLOR asked whether the constant "acid value" of the resins had any specific value apart from its relative value, because if it had it must be of considerable value, and if not he took it it was of small value. He was rather surprised to hear Mr. Cowie remark that scammony and jalapin could be distinguished by colour; he did not think that was so with the commercial article. Mr. D. B. DOTT said some years ago he called attention to the importance of using absolute ether in testing for resins. Successive pharmacopoeias described as ether what was really a mixture of ether and alcohol. In regard to the drying of these resins and other substances, sometimes it was an advantage to get rid of the last traces of water and spirit by drying in a vacuum. The PRESIDENT remarked that the solubility of many resins diminished the longer they were kept. Mr. F. H. ALCOCK said with reference to the difficulty of removing the last traces of water from such substances as the resins of scammony, jalap and other drugs, advantage might be taken of the process suggested by Professor Young in a paper read before the Conference at its last Bristol meeting for the removal of water from alcohol. He (the speaker) recalled the process, which consisted in adding benzene, when on distillation the water came over first, then the benzene with alcohol, and finally alcohol, which was anhydrous. He also said that it should not always be concluded that all loss at 110°C., or even 100°C., which was driven off from such substances as drugs, was water, and thought that oftentimes volatile products, probably of decomposition, might also pass away, as was the case with saffron and some other drugs, especially when in powder. In this connexion he stated that it might be worth while to try and find out the amount of loss by weight which drugs suffered at 100°C., and compared this with the gain which followed when they were exposed to air again. Mr. WILLIAM DUNCAN inquired what Mr. Cowie meant by jalap |