3. The small fraction collected at 250-275° C., afforded after repeated rectification over metallic sodium a colourless, limpid liquid, boiling at 255-260° C. It was analysed with the following

The molecular formula of this fraction in view of its high boiling point is undoubtedly a multiple of the simple formula C10 H16, and would be more correctly expressed by the formula C1, H, in accordance with the molecular formula of those terpenes having similar boiling points. Its specific gravity is 0.912 at 21° C.; its rotation in sodium light, in a tube of 100 mm., at 25° C., is 9° 2′ to the right.

The liquid portion of Mitcham peppermint oil is thus seen to consist simply of isomeric and polymeric terpenes, containing no menthene, as might be supposed from the dehydration of the menthol, and the absence of compound ethers in the oil is also herewith established.

According to Beckett and Wright, the liquid portion of Japanese peppermint oil contains a small amount of a substance isomeric with borneol, an inference drawn from analytical numbers obtained from a fraction boiling at 210-215°, and which by treatment with zinc chloride yielded principally menthene.

That no body of the formula C10H18 O is present in the liquid portion of Mitcham peppermint oil is conclusively established by the analysis of the oil itself, previously freed as completely as possible from menthol, and before treatment with metallic sodium. As has been pointed out in "Pharmacographia," some specimens of peppermint oil are capable of yielding a small amount of a crystalline compound with alkaline bisulphites. This observation we have now confirmed with the crude Mitcham oil; the body in question appearing, however, to be principally contained in the so-called "extra strong oil," and has, therefore, probably a boiling point approxima ting closely to that of menthol. It is furthermore contained in the oil in such exceedingly small amounts that its isolation for the present must remain uneffected.

It would also seem possible that to this body the remarkable colour reaction and fluorescence is due, which is displayed by fresh peppermint oil, when allowed to remain a short time in contact with a few drops of nitric acid, sp. gr. 1.20, as the reaction is not displayed by the terpenes, nor by the menthol. Peppermint oil by age gradually loses the faculty of assuming this coloration with nitric acid, which would also point to a substance easily undergoing chemical change. We have had as yet no opportunity of submitting the terpenes of peppermint oil to oxidation, which should form a subject for a special study, although it is probable that the lower boiling fractions would furnish the same products as turpentine oil, and terpenes having similar boiling points, viz.: acetic, terebinic, terpenylic, and terephthalic acids; while menthol, according to the observations of Oppenheim, † is converted by oxydizing agents chiefly into what he calls "resinous bodies."

The PRESIDENT said the Conference was much indebted to the authors for this paper, which had a considerable bearing on the question of the adulteration of these oils.

Dr. POWER regretted that he was not able to present specimens of these products. It was a remarkable fact that the liquid portion of peppermint oil when entirely free from menthol had an odour entirely distinct from peppermint, but somewhat reminding one of lemon oil, though corresponding more nearly to that of freshly distilled turpentine oil.

Professor ATTFIELD remarked that one paragraph in the paper illustrated very well the risks run by experimenters who depended upon certain commercial articles. The presence of the alcohol in one of the samples examined showed that when essential oils were to be investigated, for purposes of original research, they should be either carefully isolated by the experimenter himself, or obtained from a manufacturer who would guarantee their purity.

Mr. MASON said he believed the specimen referred to was manufactured on the continent. It was quite unusual for oil of peppermint to be adulterated with alcohol in this country.

Mr. GREENISH thought the results showed that adulteration varied over a large number of specimens, and it was difficult to determine what could be relied upon unless the experimenter were present, and saw the oil made, or made it himself. It seemed as difficult to

* See "Pharmacographia."
t Comptes Rendus, lvii., p. 360

obtain pure peppermint oil as genuine port wine, which, it was said, could only be secured by going to Portugal and buying a cask, and sitting on it all the way home. In many of these experiments the results could not be relied upon simply because the article was not genuine.

Dr. SYMES thought some of the results obtained would be due to the presence of a resinous matter, and this would vary with the age of the oil. Probably some of the resinous matter would be produced in the distillation, and there would be some oxidation which would also vary in different samples. He should like to know if the experiments had been conducted with oil of a known age or with specimens of different ages, and whether the amount of resin was found to be constant in different samples.

Mr. UMNEY said the Mitcham oil of peppermint would always contain a large amount of this resinous principle, and its presence was owing to the crude way in which the essential oil is manufactured. If any one visited the fields at Mitcham, Carshalton, or the neighbourhood, he would see the herb cut with a sickle and thrown bodily into a still, not heated by steam but by direct fire, and very often some portions get actually charred; thus the empyreumatic matter was driven over, and a large quantity of resinous matter would be present in the oil. He considered that no specimen of English manufacture could be considered pure unless it had been rectified the second time with water, and then a very small quantity of resinous principle would be present.

Mr. REYNOLDS said it was quite necessary to go beyond the mere fact that an article was called "best," because unless there was something added to the superlative, the mere market name carried no guarantee of purity. He had just lit upon a quotation from Southey, in which he said that there was an ingenious tradesman who sold gloves, and whose worst gloves were distinctly known as "best. He had, however, four other kinds, which he called "better than best,' ""better than better than best,' 99 66 'best of all," and "the

THE RESTORATION OF DISCOLOURED SYRUP OF IODIDE OF IRON.

BY THOMAS B. GROVES, F.C.S.

Numberless articles by accredited writers in the Pharmaceutical Journal and elsewhere have shown that the preparation of a nearly colourless syrup of iodide of iron is not a difficult matter, and there has been a pretty general concurrence in the belief that the process of the British Pharmacopoeia leaves little to be desired. As to its keeping properties, there has been and probably there still is a good deal of difference of opinion; some going so far as to say that it keeps perfectly well, and needs no special precaution for its preservation, whilst others have devised elaborate ways of bottling and storing or chemical treatment intended to enable the pharmacist to dispense a creditable article when called upon by the prescriber. It is doubtless true that when made with pure sugar, a substance by the bye difficult at all times to procure, the syrup, when in reasonable demand, does keep fairly well, so well in fact that well accustomed dispensing establishments fail to see any difficulty in the matter. Such, however, is not the case with those who perhaps are not called upon to dispense the article once in a month, or even less frequently. Then, on searching the cupboard, it is often found that the syrup without some treatment is not presentable, and frequently it happens that for want of knowing what to do in the case the syrup is sacrificed and the patient incommoded. With the view of assisting my brother pharmacists when in this dilemma, I venture to offer a few observations. I must, however, confess that instances have to my knowledge occurred where the pharmacist has not been too scrupulous, and ignoring the refinements of pharmacy has not hesitated to supply his customer with a discoloured syrup. I have myself been hauled over the coals for supplying a colourless and comparatively flavourless article, "apparently not so strong as Mr. Dash's"; in fact have suffered for a time, as did George the First's cooks, who supplied his majesty's table with fresh oysters, "not so 'igh in flaviour" as those to which his Hanoverian Highness had been accustomed.

The discoloration of syrup of iodide of iron is doubtless due mainly to the presence of free iodine; when turbidity is present there is probably also a basic persalt of iron in suspension, which adds to the effect. To get rid of both of these it is only necessary to dilute the syrup with say a third of its volume of water, to boil

briskly for a few minutes, then filter through paper, and finally reduce by evaporation to its original bulk. The syrup will then have resumed its original appearance.

The strength of the preparation will not have been materially altered by this treatment, for it takes a wonderfully small quantity of iodine in the free state to colour a large amount of liquid. Thus it will be found that one drop of liquor ferri perchloridi added to half a fluid ounce of freshly prepared syrup of iodide of iron will produce in it the tint of golden sherry, to be completely dissipated by a few minutes' boiling. There is, I am aware, nothing new in this treatment by boiling, etc.; it has, I know, been mentioned already by some writer whose name I have unhappily forgotten, but whose useful though often unused suggestion has not escaped me.

I will now refer to some experiments I have recently made in the same direction, and haxing for their object the avoidance of the delay attendant on the process already mentioned.

The text-books tell us that when a persalt of iron is brought in contact with a soluble iodide, the salt is reduced to the proto condition, and free iodine is eliminated. It was at one time thought that under these circumstances a per-iodide was formed, but Mr. Squire, junr., some years since proved conclusively that such was not the case by showing that the colour could be removed from such a liquid by simply shaking it with an ordinary solvent for iodine, such as benzine or chloroform. If to such a liquid containing iodine in solution, caustic potash or soda be added, precipitation of ferric oxide will result, and the iodine will combine with the base of the precipitant. Applied to a discoloured syrup of iodide of iron the process does not answer, and that in consequence of the sugar, as it appears to me, exercising a solvent action on the precipitated oxides. In fact it is after filtration more discoloured than ever.

In a paper published in the ninth volume, second series, of the Pharmaceutical Journal ("Preservation of Syrup of Iodide of Iron "), I pointed out the effect produced by the presence in the syrup of a trace of phosphoric acid, how that by seizing at the moment of its formation the peroxide of iron and rendering it insoluble, it effectually prevented the reaction ending in the elimination of free iodide that would otherwise have resulted. Syrup, even dilute, will keep for years after being so treated, but of course one gets instead of the discoloration the slight turbidity occasioned by the deposit of perphosphate of iron; this however, being colourless and easy of removal by deposit or filtration, is of but little moment. Addition of phosphoric acid to syrup already discoloured