attended with considerable difficulty. Of the impurities most commonly occurring, arsenic, lead, copper and silver are the most important. The bismuth may be freed from the first two of these, if present, with comparative ease, by a simple metallurgical operation which consists in fusing it with nitre, as directed in the Pharmacopoeia. This is the process usually adopted, and which answers best for removing the more oxidizable metals. It may be conveniently and successfully applied to quantities of the metal varying from four ounces to a pound by means of a gas furnace. The process, however, is insufficient for the removal of copper and silver; and it is with reference especially to the former of these that the principal difficulty is experienced in purifying some of the crude bismuth and bismuth ores of commerce. At the present time large quantities of Australian ore, rich in copper, are waiting the discovery of a method by which the bismuth it contains may be economically separated in a state of sufficient purity to admit of its being used for pharmaceutical purposes. When this question has been satisfactorily solved, there is every reason to believe that a great reduction in the price of the metal will take place. In the meantime we shall have much impure bismuth, containing copper, which, although applicable for one of the purposes for which bismuth is required, -namely, the preparation of fusible metal,-is not well suited for the production of the compounds of bismuth used in medicine. Already the attention of metallurgists has been directed to the importance of providing a supply of purified bismuth for pharmaceutists, and I am assured by houses extensively engaged in this branch of metallurgy that bismuth, free from arsenic, copper, or any material impurity, may now be obtained by those who are willing to pay the price for it.* As this purified bismuth is prepared by men accustomed to such operations from the ores which yield it most readily, it will be found the most economical and best course for those who require pure bismuth to buy the metal in the purified state, or otherwise it will be necessary, in applying the process of the Pharmacopoeia, to use crude bismuth which is free from copper and silver. * I have recently purchased such at 20s. a pound, the price of crude bismuth being at the same time 18s. a pound. With reference to Liquor Bismuthi et Ammonia Citratis, on which there has been some correspondence in this Journal, it may be stated that, if the conditions specified in the Pharmacopoeia be fulfilled, that is to say, if the bismuth employed has been purified in the manner described, and if the purified metal, and also the solution prepared from it, answer to the tests as given, the latter will be free from arsenic, lead, copper and silver. These are the impurities most likely to occur, and to the removal or detection of which the process of purification and the tests of the Pharmacopoeia are directed; but if it were the object of a manufacturer to introduce other impurities which would elude detection by the tests as given, it would no doubt be possible to do so. I have recently inet with two instances of such adulteration in subnitrate of bismuth, an account of which will be found in the following article.-Lond. Pharm. Journ., August, 1868. NOTE ON A NEW ADULTERATION OF SUBNITRATE OF BISMUTH. BY DR. REDwood. I have recently had occasion to examine two samples of subnitrate of bismuth, which have proved to be adulterated to a great extent, by the admixture of a substance which none of the tests usually applied would detect. These samples were sent for examination by wholesale druggists who had been led to suspect. that they were not genuine, but who were greatly surprised to learn the extent and nature of the adulteration. The first of the samples was sent me last May. It presented the usual appearance of the variety of subnitrate of bismuth generally met with in commerce in the form of powder, without any crystalline character. It dissolved in nitric acid with a slight evolution of carbonic acid gas, and this had caused it to be condemned as impure, by a customer to whom it had been sent. The quantity of carbonate present in it was, however, extremely small. In other respects it answered to the Pharmacopoeia tests, excepting that the solution in nitric acid gave a precipitate with nitrate of silver, indicating the presence of oxy chloride. This is so frequently met with in commercial subnitrate of bismuth that its detection would not have excited much surprise. Its presence is excused by manufacturers on the ground of its making the powder more suitable for some of the purposes to which it is applied, so that for such purposes the powder would be unsaleable if it did not contain any chloride. The chlorine having been estimated, and the equivalent quantity of oxychloride calculated therefrom, a further examination rendered it evident that there was something else present besides subnitrate of bismuth. The residue left, after calcination, was in excess of that which theory indicated; and this residue dissolved in nitric acid, mixed with dilute acetic acid, and precipitated with sulphuretted hydrogen, gave an amount of sulphide much below the theoretical quantity. The cause of these discrepancies was found in the filtrate, which yielded an abundant precipitate of phosphate of lime. While I was engaged in this investigation, my attention was directed to a paper in the " Journal de Pharmacie et de Chimie" for last March, by Mr. Roussin, in which he alludes to the adulteration of subnitrate of bismuth with phosphate of lime, and describes a very simple method of detecting it. Mr. Roussin says that in one case he found as much as 28 per cent. of phosphate of lime in a sample which presented the usual appearance, and answered to the ordinary tests of subnitrate of bismuth. His process for its detection and estimation is as follows: Dissolve equal quantities of the subnitrate and of tartaric acid in nitric acid slightly diluted with water, and add to this a strong solution of carbonate of potash until all effervescence has ceased, and the liquid is rendered strongly alkaline. "If the subnitrate of bismuth be pure the liquid will be clear, and will remain so even after it has been boiled; but if the sample of subnitrate submitted to the test should contain phosphate of lime, even to the extent of 1 or 2 per cent., this will form a white precipitate, which will not dissolve with long-continued boiling." In applying this test, it is important to observe that the phosphate of lime, even when present in large quantity, is not precipitated in the first instance after the addition of the carbonate of potash, but its precipitation is immediately effected by boiling the solution. From the sample to which I have already referred, I obtained in this way 11 per cent. of phosphate of lime; and from another sample, which came from a different source, I have more recently obtained no less than 40 per cent. of the same adulterant. I have reason to believe that both these samples were of foreign manufacture.-Lond. Pharm. Journ., August, 1868. ON NITRATE OF AMMONIA AND NITROUS OXIDE. [From White's Dental Materia Medica, Phila., 1868.] Nitrous oxide for anæsthetical purposes has come into such general use, that information is constantly asked in reference to its properties; the materials used in its manufacture; the process of generating it; how to determine the purity of the nitrate, and of the gas when made, etc. As found in commerce, nitrate of ammonia is crystallized, granulated, and fused. The fused salt is made by melting down the crystals, and allowing them to solidify into a compact mass on cooling. The granulated is made by evaporating the solution to such a density that it would solidify on cooling, then reducing the heat and stirring the mass until it cools. The three varieties are all more or less deliquescent, and should be kept in a dry place, excluded from the air. The fused is generally preferred, because the amount of gas given off by equal weight of the three varieties is somewhat in favor of the fused and granulated, and the latter is objected to by some on account of its greater liability to absorb moisture and gain weight by exposure to the air. If pure, when heated on platinum foil the nitrate should volatilize completely. A residue of any considerable amount would indicate the presence of some non-volatile salt-probably nitrate of potash or soda. A solution of nitrate of ammonia should not afford a precipitate on addition of a few drops of chloride of barium, which would indicate sulphuric acid; nor on the addition of a few drops of a solution of nitrate of silver, which would indicate the presence of chlorine. Sulphates and chlorides are almost always present in commer cial nitrate of ammonia; but if the solution is rendered only turbid, without affording an immediate precipitate with the above reagents, it is sufficiently pure. The various effects of increasing heat upon nitrate of ammonia are shown by the following table: At 226° F. fuses perfectly. At 302° F. emits white fumes, condensing in drops. At 347° F. effervesces slightly. At 356° F. boils without decomposition. At 437° F. effervesces rapidly. At 460° F. begins to evolve gas. To determine the temperature, thermometers have been prepared which may be passed through the cork and into the retort, marking the following degrees: 226°, 356°, 460°, 482°, 500° F. To obtain the largest amount of gas, the nitrate should first be melted in the retort at a temperature just sufficient (226° to 250° F.) When melted, the heat may be at once carried up to the point of decomposition, 460° F. If a gradually increasing heat is used after the salt is melted, a portion of it will sublime unchanged until the temperature reaches 460° F. The heat should never be allowed to rise above 482° F., for beyond that noxious products are generated. After the gas has begun to come over briskly, the appearance of copious white fumes in the retort is an indication that the heat is too great. The nearer the heat can be kept at the point necessary to generate nitrous oxide, the purer will be the gas. After the decomposition has fairly commenced, the heat must be lowered rather than increased, as by that time the sand, retort, and the salt itself have accumulated enough heat to carry on the generation of gas for some time, even if the flame were entirely withdrawn. A sand-bath should always be used to protect the retort from the direct heat, which may be supplied by means of a suitable gas-burner, or by an alcohol or kerosene lamp. The retort must be of glass; no other practical material has yet been found to answer the purpose. The retort is usually |