ON SOLUTION OF MAGNESIA. BY MR. JOSEPH LEAY. THE solution of bicarbonate of magnesia is a preparation which has been sanctioned and prescribed by medical men for several years past, and may now be considered an established article of our Materia Medica. The strength and purity of such a solution is so easily ascertained, that I am really surprised that any one should be bold enough to bring before the public, under the above name, a preparation that will not stand the test of examination; yet it will be found that much of the solution of magnesia of commerce is not only very deficient in strength, but that in some cases it contains other salts besides the carbonate of magnesia in solution. Many persons who have attempted the manufacture of this solution, have fallen into the error of using the common carbonate of magnesia of commerce, which, having been dried, is much less easily dissolved, through the agency of carbonic acid, than the recently precipitated but undried carbonate would be. This no doubt is one cause of the very deficient strength of much of the solution sold. There are, however, some makers in this and other towns through the country, who adopt a very easy, expeditious, and economical method of making what they call solution of magnesia. This consists in simply dissolving sulphate of magnesia and bicarbonate of soda, or bicarbonate of potash, in water. I need hardly say, that after separating the carbonate of magnesia from this by boiling it, sulphate of soda will remain in solution. It is said that some medical men approve of the preparation made in this simple manner, and do not object to the presence of the purgative salt which it contains. Be this as it may, it is surely desirable that there should be some other name applied to this solution, so as to distinguish it from the simple solution of bicarbonate of magnesia. The latter solution requires an expensive apparatus for its proper preparation, while the former may and ought to be made by every dispensing Chemist for himself. The subject is one which I think ought to be brought under the notice of the Pharmaceutical Society, as the best means of making the Chemists and Druggists and the Medical profession aware of the great discrepancy there is in the composition of the preparations sold under the name of "Solution of Magnesia." 137, Broad Street, Birmingham. A MEMBER present alluded to the deposition which takes place in the bottles containing the solution of magnesia, even that sold by the original makers, and thought this must materially affect the strength of the solution, as he sometimes found large crystals in the bottles. Mr. REDWOOD said he could confirm the statement of Mr. Leay with regard to the difference in the strength and composition of different specimens of solution of magnesia, and it was very important that Medical Men and Dispensing Chemists should be aware of this want of uniformity, as the preparation was frequently ordered in prescriptions. Mr. Dinneford and Sir James Murray were justly entitled to the credit of having introduced this very elegant and useful remedy to the notice of the public. They were the first makers, and, he believed, they continued to be among the best makers of it. No secret had ever been made of the composition of the solutions sold by these makers. Mr. Dinneford's solution was stated, on the authority of Professor Brande, Dr. Paris, Dr. Wilkinson, and Dr. O'Shaughnessey, to contain from seventeen to nineteen grains of carbonate of magnesia in every fluid ounce; and Sir James Murray's solution was stated, on equally good authority, to contain about thirteen grains in the fluid ounce. Now it was upon these preparations, being those first introduced to notice, that the reputation of the remedy had been founded. Mr. Dinneford's was probably as strong a solution as could be made, and might be fairly taken as a type of what the preparation ought to be. But Mr. Dinneford made no more secret of the method of making his solution than he did of the composition of it, and the manufacture was therefore open to free competition. There were, as Mr. Leay had stated, several manufacturers in different parts of the country, and he (Mr. R.) had examined the solutions produced by some of these makers, and found them to be very different from those of the original makers. Thus, for instance, in one case be found only as much magnesia present as was equivalent to about four grains of the hydrated carbonate of magnesia of commerce in the f3j., while the solution contained at the same time sulphate of soda and a small quantity of sulphate of potash, from which it was evident that it had been made by dissolving sulphate of magnesia with bicarbonate of soda and bicarbonate of potash, in water. These ingredients, in the proportion of fourteen grains of crystallized sulphate of magnesia, seven grains of bicarbonate of soda, and two-and-ahalf grains of crystallized bicarbonate of potash, to one ounce of distilled water, formed a solution identical with that to which he had alluded. Now, it was very evident that this formed a solution which could not be substituted for that originally introduced under the name of "Solution of Magnesia." Then, with regard to the statement of the last speaker, that the solution made by the original makers was liable to a deposition of magnesia on the inside of the bottles, he thought it much more important that the solution should be of uniform strength than that it should be in the most highly concentrated state when first prepared. He would advise the manufacturers of it not to attempt to make it of greater strength than that at which it could be kept unaltered for a reasonable length of time. Under all the circumstances which had been stated, it was obviously necessary that every Dispensing Chemist, before using any specimen of solution of magnesia in a prescription, should first ascertain the strength and composition of the solution. He recommended the following simple method of examining it: Evaporate a fluid ounce of the solution to dryness in a Wedgwood dish; calcine the residue at a red heat for about five or ten minutes, in a small Berlin crucible; then weigh the calcined residue. If this residue be pure calcined magnesia, every five grains of it will be equivalent to twelve grains of the hydrated carbonate of magnesia, or Magnesia alba of commerce. After weighing the calcined residue, treat it with distilled water, when, if there be any soluble salts present, they will be dissolved out, and may be tested, weighed, and the amount deducted from the weight of the magnesia. LIST OF MEMBERS, ASSOCIATES, AND APPRENTICES (CONTINUED). Walbran, Thomas F., Westgate BURY ST. EDMUNDS Chaplin, Alfred, Church Street *Davies, Elijah Knox, 1, Brunswick Place, Portway, John, Abbeygate Street Buck, William, 28, High Street LONDON Allen, Arthur, 22, Holles Street Crossley, John, 41, Bishopsgate Street MIDSOMER NORTON Dudden, Richard Mogg MILTON Sutton, George, High Street Kirkbride, William, Great Dockray Finemore, William Foot, 13, Union Street Kellett, Edwin, 2, Fylde Road WICKHAM MARKET Clarke, Thomas Meadows, George Street Wheeler, James Edward, High Street Goodridge, William, Broad Street MAJOR EXAMINATION. ORIGINAL AND EXTRACTED ARTICLES. ON GUTTA PERCHA, A VARIETY OF CAOUTCHOUC. BY E. SOLLY, F.R.S., F.L.S.* A VERY remarkable substance, bearing the name of Gutta percha, and in many respects closely resembling caoutchouc, or India-rubber, though in others evidently distinct, has during the last year been transmitted to this country from Singapore, and brought before the notice of practical men. It was first sent over by Dr. Montgomerie, who received the gold medal of the Society of Arts for its introduction into this country, as a new and hitherto unknown substance likely to be useful for various purposes in the arts. He was, however, it appears, unable to ascertain its history further than that it could be obtained in very large quantities, and at a moderate price, being used by the natives as a substitute for horn and wood for a variety of purposes, more especially to make the handles of knives and choppers, as from its peculiar nature, though easily softened by the application of heat, it remains firm and hard at ordinary temperatures, allows a very firm hold to the hand, is very lasting, and not subject to decay of any sort—hence it is even said to be preferred for these purposes to buffalo-horn. The tree which yields it, and the mode in which it is prepared, are unknown; it is, however, stated that it is procured by cutting down the trees, a most wasteful and unnecessary proceeding. It it probable that the sap or juice of the tree is rubbed over a smooth surface, and on drying leaves a coating of the substance of greater or less thickness, and that these films are subsequently joined or rolled together into solid masses. The first specimens brought to this country-both that sent to the Society of Arts, and also samples which I received at the same time from Dr. Royle, from the East India House-were in two forms, namely, thin scraps resembling in appearance clippings of white leather, and solid rolls, which, when cut across, exhibit the end section of the thin layer, by the junction of which the mass has been formed. These masses are far from being pure, a considerable quantity of sawdust and other vegetable and mineral impurities being entangled between the layers. As gutta percha is beginning to excite a good deal of interest, and appears likely to become an article of considerable importance in a commercial point of view, I have thought that a * Read June 23d, 1845, at the Cambridge meeting of the British Association.-Gutta percha was first brought before the Society of Arts in the autumn of 1843. It is mentioned in the Gardener's Chronicle, Dec. 9, 1843. |