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Mr. Redwood thought it should be understood, that although the Tinnivelly senna was recommended as being nearly as good as the Alexandrian, it would not be justifiable on any account to substitute for it the common East Indian, which, although originally the same species, was very inferior in quality a result probably depending on the mode of cultivation.

ON AN EXPLOSIVE COMPOUND FORMED DURING

THE DISTILLATION OF HYDROCYANIC ACID.

BY MR. ALSOP.

The late catastrophe at Apothecaries' Hall, on the preparation of fulminating mercury, has recalled to my recollection a circumstance which took place several years since, which may probably be interesting to the members of the PharmACEUTICAL Society.

At the time adverted to, I was residing at the house of John Bell and Co. and we were accustomed to prepare hydrocyanic acid, by distilling the bicyanide of mercury with hydrochloric acid; on one occasion the process was stopped before the whole of the prussic acid had been evolved from the materials in the retort, which were therefore reserved to be added to a future distillation. This liquid, retaining strongly the hydrocyanic odour, was transferred to a stoppered phial and kept in a dark closet for two or three months. It was subsequently submitted to distillation, together with fresh materials, in a retort capable of holding about four pints, and which was more than half full. The heat of a lamp had not long been applied to it, when an opalescent appearance was manifested, and a gradual formation of exceedingly minute and pearly crystals was observed to pervade the liquid. This was doubtless no other than fulminating mercury. At first it was supposed to be protochloride of mercury, arising from the decomposition of a protocyanide which appears sometimes to be formed by acting on Prussian blue, and therefore did not attract much attention, notwithstanding its suspicious appearance. This deposit continued to increase ; it was left for a few minutes, and happily no one was present, when the laboratory was shaken by a most alarming explosion. The contents of the retort were discharged on the ceiling, showing that the explosion had taken place from the bottom, to which the deposit had subsided. The fragments of the retort were also entirely dispersed—tradition says, they were no where to be found.” The laboratory man in alarm rushed into the apartment, and was in great danger from the hydrocyanic vapour, when he was hastily removed.

The circumstance is curious, as presenting the formation of this dangerous substance where it was quite unlooked for; and, although the fulminic acid appears to be isomeric with the cyanic, it is rather difficult to account for the formation of an oxygen acid united with an oxide, from the elements concerned, viz. bichloride of mercury, bicyanide of mercury, and hydrochloric and hydrocyanic acids, unless in some way water had been decomposed, and the hydrogen liberated or disposed of. The bicyanide was prepared by boiling red precipitate with Prussian blue, whether, in this instance, well crystallized salt only was employed, I cannot now say, but, on considering the subject, I strongly incline to the opinion, that nitric acid must have been present, probably from its not having been perfectly expelled in the preparation of the red precipitate.

While on this subject, I will advert to a remark common in early chemical works, that hydrocyanic acid has the property of expanding to five times its bulk any gas with which it may be mixed, and that many dangerous explosions have arisen from this cause, on which account capacious vessels are directed to be employed in its preparation. I have never observed any such mischievous expansibility in the ordinary form in which it comes over, and should explosions have arisen from the concentrated acid, I should rather apprehend it might have arisen from its passing into the gaseous state by change of temperature, in vessels not large enough to allow of its expansion, or not strong enough to bear it, rather than from any mysterious propensity of outriding any other gas with which it may come in contact. Another conjecture arises, whether these early operators may not have encountered unawares, some of these dangerous fulminates or nitrurets.

Professor Clark thought Mr. Alsop's paper valuable in a practical point of view, as it was desirable to know under what circumstances accidents of this kind were likely to take place, even although the cause could not be satisfactorily explained. He thought in the present case the explanation given by the author might be questioned, as he could not account for the formation of fulminating mercury under the circumstances. He might observe, however, that the muriatic acid, even that which is sold as pure, frequently contained arsenic; and it was well known that some of the compounds of arsenic were explosive. This was also the case with some of the salts of tin.

The Chairman hoped the information contained in Mr. Alsop's paper would prove a warning to young men who might be engaged in experiments. It might not, perhaps, be an unsuitable

time to make a passing allusion to the late melancholy event at Apothecaries' Hall. Mr. Hennell had been a fellow-student, and was always an enthusiast in pharmaceutical and chemical pursuits. During an interview which he had with him a short time before his death, he (Mr. Hennell) expressed great interest in the success of the PIARMACEUTICAL SOCIETY, and regretted that he had not yet been able to attend any of the meetings.

ON ANNUAL AND BIENNIAL HYOSCYAMUS.

BY JOSEPH HOULTON, M.D. I beg leave to direct the attention of the Puarmaceutical Society to the consideration of an annual cultivated hyoscyamus which is now in season, and which has so much of the appearance of the true hyoscyamus niger, that it may be easily taken for that plant; yet a practised botanical eye can readily detect the difference.

Observing in that excellent work of Dr. Pereira's on Materia Medica, that there is an annual variety cultivated at Mitcham, I wrote to Mr. Tipple, surgeon of that place, who politely furnished me with some of the seeds, which I sowed in my garden in March last, and the plants are now in flower.

The flowering period of the true indigenous hyoscyamus niger is now, I believe, past, yet I have some reason to think that we shall for some weeks to come be supplied with a fine fresh flowering hyoscyamus, that is the annual." I was yesterday in the Royal Botanical Gardens, Regent's Park, where I saw plenty of the annual but none of the biennial hyoscyamus. I am now not surprised that authors should disagree respecting the duration of this plant. Thus we see in Alston, the black (henbane) is always biennial; Bergius, biennis ; J. A. Murray, biennis. In Smith, Hooker, Duncan, &c., annual.

I am not at present able to determine the botanical relation of the annual to the true hyoscyamus niger in its degree of affinity, nor am I able to give any information respecting the difference in the medicinal properties of these two plants—these are two important points, and deserve to be carefully investigated; and I hope before next season we shall be in possession of that knowledge, ly the labours of some who are competent to carry on the enquiries in a proper manner.

The Chairman enquired whether any Member present had observed a difference in the medical properties between the cultivated and the wild hyoscyamus, and observed that cultivation

might convert the biennial plant into an annual, as was known to occur in some cases. He regretted that the author of the paper was not present, having understood that it was his intention to bring specimens.

Mr. Squire said, that although he gave a preference to the wild hyoscyamus, he did not consider the difference between that and the cultivated to be very great.

Mr. Davy had not been able to discover any difference between the wild and the cultivated hyoscyamus, either in the plant or extract.

ON THE OXYGENIZEMENT OF ADEPS FOR THE PURPOSE OF FACILITATING THE MANUFACTURE

OF UNGUENTUM HYDRARGYRI.

BY MR. J. WALTON.

Mr. James FISON (page 662, Ph. Journ.) states, that the rancid tallow obtained from candles which have been long kept (he particularizes London moulds) is identical with the prepared sævum. I have had extensive experience both of this and of a similar article “ Nash's Magnetic Adeps," and have met with signal success in reducing by their means the time and labour usually requisite in making mercurial ointment. I feel satisfied that Mr. F. has come to too hasty a conclusion. Rancid tallow, or indeed rancid fat of any kind, will expedite the manufacture of this ointment, and it is probably to this cause that we are to attribute the beneficial results mentioned by Phillips in his notes on Mercurial Ointment, in his translation of the London Pharmacopeia of 1836, and found by experience to be produced by using a portion of old ointment to rub down the mercury when making a new quantity. The increased facility in making the ointment experienced by using adeps which has become partially oxygenized by exposure to the air, renders it a desirable object to find out some mode of imparting the same qualities artificially. This

may be effected in the following manner :- To a pound of Jard melted in an earthen vessel, add an ounce of strong nitric acid, and stir briskly for five minutes with a bone spatula. Then set aside to cool. When solid, pour off the nitric acid which has separated, and melt the lard again with four or five parts of water. Repeat this process, till the acid is completely washed off, which may be known by the taste and usual tests. The lard will be found to have acquired a firmer consistence, a granular appearance, and a somewhat rancid smell. Though containing no acid whatever, it has the property of oxydizing mercury with very great rapidity. I have enclosed a sample for your inspection, as it is of importance to the adoption of the practice, that

no acid should be proved to exist in the lard, which on examination, you will find to be the case. By employing the oxygenized lard, it is possible to make ointment as perfectly in a quarter of an hour, as by the old process in a day. I conceive this to be the preparation, the sævum before alluded to, undergoes, as the similarity in appearance and effects is exact.

6, Broad Street, Bath.

Mr. Redwood said, that in connection with the consideration of Mr. Walton's paper he took the opportunity of bringing under the notice of the meeting some lard, prepared according to a process to which he had alluded on a previous occasion. The process adverted to is as follows :-The lard is melted in an earthen pipkin, and while in the fluid state, poured in a thin stream from some height, into a vessel containing a considerable quantity of cold water. The lard diffuses itself in a thin stratum over the surface of the water: it is now to be collected and placed in a coarse hair sieve, and the top of the sieve to be covered with paper, to preserve it from the dust. In this state it should be kept in a dry apartment, exposed to the action of the air, for two or three months; at the expiration of which time it will be found to have acquired the property of readily combining with a very large proportion of mercury. This process was first suggested by M. Dorly, a French Pharmacien; and a specimen of lard thus prepared was exhibited to the Society of Pharmacy at Paris, some years back, which was stated to possess the power of killing thirty-two times its weight of mercury in a few minutes. He (Mr. R) had prepared some lard according to this process about three months ago, being desirous, in conjunction with his friend Mr. Bell, to elucidate further the phenomena connected with the preparation of mercurial ointment; and he now laid it before the meeting in the sieve in which it had remained since the 22d of April last. He begged at the same time to observe, that he was merely induced to submit it to the meeting on that occasion, in consequence of the subject having been brought forward by Mr. Walton.

The experiments, of which this was intended to be one, were not yet completed, and this, therefore, must be considered only as one link of a chain of evidence intended to determine the question as to the oxidizement or merely mechanical division of mercury in some of its preparations. In order to exhibit the altered properties of the lard, he would put part of it, with thirty-two parts of mercury, into a mortar; into another mortar he would put the same proportions of ingredients, but substituting the lard prepared according to Mr. Walton's process, a portion of which

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