von Stamm eines Ulme; that is, Chemical experiments on a gummy juice from the stem of an Elm. The substance on which his experiments were made was sent him from Palermo in 1802; and lie conjectures that the species of elm from which it exuded was the ulmus nigra. What species he refers to, by the name of ulmus nigra, it is difficult to guess; as I am not aware that any such name was ever given by botanists to any species of elm whatever. This substance, according to Klaproth, possessed the following properties. It was solid, hard, of a black colour, and had considerable lustre. Its powder was brown. It dissolved readily in the mouth, and was insipid. It dissolved speedily in a small quantity of water. The solution was transparent, of a blackish brown colour; and even when very much concentrated by evaporation, was not the least mucilaginous or ropy; nor could it be employed, like mucilage of gum, to paste substances together. It was completely insoluble both in alcohol and ether. When alcohol was poured into the aqueous solution, the greatest part of the substance precipitated in light brown flocks. The remainder was obtained by evaporation, and was not sensibly soluble in alcohol. The alcohol, by this treatment, acquired a sharpish taste. When a few drops of nitric acid were added to the aqueous solution, it became gelatinous, lost its blackish brown colour, and a light brown substance precipitated. The whole solution was slowly evaporated to dryness, and the reddish brown powder which remained was heated with alcohol. The alcohol assumed a golden yellow colour; and when evaporated left a light brown, bitter, and sharp resinous substance. Chlorine was found to produce precisely the same effect as nitric acid. When the exudation from the elm was burnt, it emitted little smoke or flame, and left a spongy, but firm, charcoal; which, when heated sufficiently in the open air, burnt all away, except a little carbonate of potash. In the third edition of my System of Chemistry, I inserted this substance as a peculiar vegetable principle, under the name of ulmin. Though I had some suspicion that it might be the same with the peculiar substance previously discovered by Vauquelin in the diseased exudation from the common elm (ulmus campestris); yet, as I had no means of verifying this suspicion, and had no hopes of being able to procure any of the exudation described by Klaproth, I did not venture to hint my suspicion, heing apprehensive that it might contribute to increase the confusion of a branch of chemistry by no means remarkable for its precision. Fortunately, Mr. Walter Coulson, on reading the account of Gehlen's Journal, vol. iv. p. 329. ulmin in my work, recollected having seen a similar exudation from an old elm in the neighbourhood of Plymouth. Conceiving that this exudation might be ulmin, he collected a quantity of it, and was so obliging as to send it to me. I seized with avidity an opportunity, quite unlooked for, of putting my conjectures to the test of experiment, and of witnessing the very peculiar properties of ulmin described by Klaproth. The substance which I examined agrees in so many particulars with the properties noticed by Klaproth, that there can be little doubt of its belonging to the same species. The few differences which I observed were probably owing to the different length of time that the substance in question had been exposed to the atmosphere. The substance which I examined being an exudation from the common elm, and agreeing in every particular with the properties noticed by Vauquelin, there can be no hesitation in considering them as similar. Hence it follows, that the vegetable substance first described by Vauquelin, and the ulmin of Klaproth, are one and the same. The following are the properties of the ulmin from Plymouth, as far as I observed them. 1. It was of a black colour, possessed considerable lustre, and broke with a vitreous fracture. It was nearly tasteless, leaving in the mouth only a very slight impression of astringency. When heated it did not melt, but swelled very much, as is the case with gum. It readily burnt away at the flame of a candle, leaving a white matter, which melted into an opake white bead, and was carbonate of potash. The proportion of this alkali was considerable, agreeing exactly with the exudation examined by Vauquelin. It contained also lime: 20 grains of the ulmin when burnt in a platinum crucible left 5 grains of residue. Of this 4.8 grains dissolved in nitric acid. The 0-2 grain of residue was insoluble, and possessed the properties of silica, tinged a little with iron. The nitric acid solution being saturated with carbonate of potash, one grain of carbonate of lime precipitated. 'Hence 20 grains of ulmin contained the following substances: Subcarbonate of potash Carbonate of lime Silica and oxide of iron ... 3.8 10 0.2 5.0 The silica and iron were probably accidentally present, and might have made their way to the ulmin while moist upon the tree; for it is probable that the dust of the road would consist chiefly of silica; or at least would be insoluble in nitric acid, the only criterion by which the O2 grains of residue were judged to be silica. 2. It dissolved readily in water. The solution was dark brown, and possessed exactly the characters described by Klaproth. It produced no effect upon litmus paper, either in its usual blue state, or when reddened by vinegar. Hence the carbonate of potash, which the ulmin contained, must have been in a state of combination. 3. No effect was produced on the solution by isinglass dissolved in water, by tincture of nutgalls, or by prussiate of potash. 4. Green sulphate of iron occasioned a very copious muddy brown precipitate. 5. Muriate of tin occasioned a copious light brown precipitate. The same effect was produced by nitrate of mercury, and superacetate of lead. 6. Nitrate of silver, caustic potash, and carbonate of potash, occasion no precipitate. 7. No precipitate was produced by alcohol, how much soever the solution of ulmin was concentrated. In this respect, my experiments differ from those of Klaproth. It is possible, that if I had employed a stronger alcohol than any I was possessed of when these experiments were made, my result might have corresponded with that of Klaproth. I had not the means of determining its specific gravity. But, as it was procured from an apothecary's shop in London, it was probably not less than 0.837. 8. Nitric acid dropped into the aqueous solution of ulmin occasious a reddish brown precipitate. The liquid being cautiously evaporated to dryness, a reddish matter remains, which is soluble in alcohol, and has a bitter taste. When heated to a temperature between 300° and 400° Fahrenheit, it takes fire even in a close vessel, and burns instantaneously like gunpowder, producing a quantity of gaseous fluid, and leaving a black spongy charcoal behind. This is owing to the nitrate of potash formed by means of the potash contained in the vegetable matter. when the precipitate is separated by the filter, washed and dried, it loses the property of exploding. When the liquid is gradually evaporated to dryness, prismatic crystals of nitrate of potash shoot at the bottom of the vessel. For 9. Sulphuric acid occasions a very copious yellowish brown precipitate when dropped into the aqueous solution of ulmin. Muriatic acid produces the same effect. When this precipitate is well washed and dried, it is a buff-coloured powder, nearly insipid, and not sensibly soluble either in water or alcohol. From these properties it is obvious, that the characters ascribed to ulmin, by Klaproth, do not apply to the substance which I examined. Ulmin might be compared to extractive; but its insolubility in alcohol seems to make it necessary to constitute it a new genus of vegetable matter. ARTICLE IV. Experiments on the Urine discharged in Diabetes Mellitus, with Remarks on that Disease.* By William Henry, M.D. F.R.S. In the analysis of the urine voided in diabètes, a few circumstances appear not to have been determined with the degree of precision which the subject admits, and which it is desirable to attain; though calculated, perhaps, rather to have an influence on the pathology of the disease, than on its medical treatment. In consequence of the recent occurrence of two cases of diabetes mellitus under my own care, and of other opportunities for which I am indebted to my colleaguest in the Manchester Infirmary, I have lately been enabled to examine several specimens of this variety of morbid urine. The results, I am well aware, do not present any facts of great novelty or importance. Yet they may, perhaps, not be unworthy of being laid before the Society; since they contribute to furnish tests of the existence of the disease, and of the degree in which it is affected by diet or remedies, which are more easily applicable than those hitherto employed. Without entering, therefore, at large into the chemical history of diabetic urine, I shall limit myself to the description of a few of its properties, to which I have particularly directed my attention. 1. Of the Specific Gravity of Diabetic Urine, and the Proportion of its solid Contents. The specific gravity of the urine, discharged in diabetes mellitus, has been left unnoticed by some of the best writers on its chemical history, as Cruickshank, Nicholas and Gueudeville, and Thenard. In about ten cases where I have had an opportunity of determining this property, it has never fallen short of 1028, nor exceeded 1040; 1000 parts of water at 60 Farh. being taken as the standard. This appears to agree very nearly with the experience of the few writers who have noticed its relative weight, and especially of Dr. Bostock, Mr. Dalton, § and Dr. Watt. || The circumstance of specific gravity I consider as a most useful test of the existence of diabetes in doubtful cases; and, when the disease is unequivocal, taken along with the actual quantity discharged, it furnishes a good criterion of the degree of morbid action. Healthy urine I have never found, * Read before the Medical and Chirurgical Society, March 12, 1811. + Drs. Ferriar, Bardsley, Holme, and Mitchell. Med. Memoirs, vi. 241. Cases of Diabetes, &c. p. 79. Dr. Bardsley's Med. Reports, p. 161. even in its most concocted state (viz. when voided on first rising in the morning), and when an average has been taken of that of several different persons, to have a higher specific gravity than 1020. In the course of the day, also, it falls greatly below that number; while the specific gravity of diabetic urine, though subject to a little variation, never changes during the same day to any thing near the same amount. It may be objected, perhaps, to the employment of this test, that it requires, more familiarity with the method of taking specific gravities, than falls to the lot of the greater part of medical practitioners. By means, however, of an hydrometer, which is well known to practical chemists, and which may readily be procured at a small expense, the specific gravity of the urine may be taken in a few moments, and with the greatest accuracy, by a person wholly unaccustomed to experiments of this kind.* Respecting the proportion of solid contents, obtainable from diabetic urine, little agreement, as might be expected, is to be found among authors; for besides that the amount actually varies, it must necessarily depend greatly on the degree to which the evaporation is carried. In Captain Meredith's case, described by Mr. Cruickshank,† it appears, at the maximum, to have constituted rather more than of the urine; Dr. Bostock, in a case which he has related in the Memoirs of the Medical Society of London, obtained of a thick syrup; Nicolas and Gueudeville of a mass resembling coarse sugar§; and Thenard from to By this process, it will always be found difficult to obtain an exact comparison between the urine of different persons, or of the same patient at different stages of the disease. It appeared to me, therefore, desirable to connect, by a set of careful experiments, the quantity of extractive matter with the more certain character of specific gravity. From such a series of experiments, I have constructed the following Table, which exhibits, at one view, the quantity of solid matter in diabetic urine of different specific gravities between 1050 and 1020. It will be easy, however, to extend the scale, by the rule of pro portion, to any case in which the urine may be found to have a specific gravity above the former, or below the latter, of those two numbers. In the experiments, which furnished the data of the Table, the urine was evaporated by a steam heat, till it *The hydrometer best adapted to this purpose is made by Mr. W. Twaddell, of Glasgow. To avoid the inconvenient length of the stem, it is divided into four parts; but it is No. 1 only of the series that is required for determining the specific gravity of urine. To reduce the degrees of this instrument to the common standard, the rule is, to multiply by 5, and then to add 1000. Thus 69 of the hydrometer denote a specific gravity of 1030; for 6 x 5+ 1000=1030; + In Rollo on Diabetes, 2d edit. p. 19. Aun. de Chim. xliv. 59. Vol. vi. p. 240. |