as occasioned by the mutual decomposition of the two salts by each other. (Ann. de Chim. et Phys. ix. 10.) XIV. Constituents of Saltpetre. In a late number of the Annals of Philosophy, I inserted a set of experiments on the analysis of this salt by Berthollet; and contrasted his results with those of Dr. Wollaston, and my own. These three sets of experiments were made in a different way. Dr. Wollaston saturated a given weight of bicarbonate of potash with nitric acid, and determined the weight of the nitre formed. Berthollet decomposed a given weight of saltpetre by heat, and measured the volume of oxygen and azotic gases evolved. I decomposed a given weight of nitre by sulphuric acid, and determined the weight of the sulphate of potash formed. It is probable that none of these methods is susceptible of absolute precision. But if each of them were performed with as much accuracy as the experiment would admit, the mean of the results obtained by the three methods would, in all likelihood, give us the true result. Dr. Wollaston's method has been recently repeated by M. Longchamp. He found nitre composed of Nitric acid (Ann. de Chim. et Phys. ix. 27.) 53.297 46.703 100.000 This result does not differ much from that obtained by Dr. Wollaston; namely, If an atom of nitric acid weigh 6.75, and an atom of potash 6, as I conceive them to do, then the true composition of nitre must be, Acid. 53.726 46.274 100.000 Dr. Wollaston's numbers approaching more nearly to these than the numbers given by Longchamp, I consider them as nearer the truth. Indeed Dr. Wollaston's results do not differ th part from the theoretical composition of nitre. Now I am afraid that it is scarcely possible to come nearer the truth than this by a single direct experiment. Chemical precision, like astronomical, can be looked for only from the mean of a great number of experiments so contrived that the errors must of necessity fall on different sides. XV. Morphia. An account of the original experiments of Sertürner on the infusion of opium, his method of extracting morphia and meconic acid from that infusion, and the subsequent trials of Robiquet and Vogel, have been already given in this journal. But no account has yet appeared in English of the results obtained by M. Franz Anton Choulant, though they have been published at least a year ago in Gilbert's Annalen (lvi. 342). As these experiments are the most minute, and probably the most precise that have been yet made, I shall in this and some of the following notices state the principal facts contained in his paper. 1. Method of procuring Morphia.-Four ounces of well-dried and pounded opium were digested in repeated quantities of cold distilled water till the liquid amounted to the quantity of about 16 English pints. This infusion was evaporated by a gentle heat on the sand-bath in a glass vessel till it was reduced to eight ounces. The whole was then poured into a porcelain evaporating dish. After standing at rest for eight hours in a temperature between 54° and 77°, six grains of small crystals were deposited, which possessed the properties of sulphate of lime. The whole, being evaporated to dryness, was redissolved in four ounces of distilled water, with the exception of a small quantity of brownish coloured resin. Oxalate of ammonia being dropped into the solution, it became muddy, and a precipitate fell, which weighed, when dry, 3 gr. After this precipitate had been separated, muriate of barytes was added, as long as it occasioned a precipitate. This last precipitate, being separated and dried, weighed two grains. The solution was now diluted with eight pints of distilled water, and caustic ammonia poured in as long as any precipitate continued to fall. The precipitate thus obtained was white and flocky. After standing two hours, it became granular and brown. It weighed six drams. It dissolved completely in eight ounces of distilled vinegar, and was precipitated by caustic ammonia without any alteration in its colour or its weight. Upon this precipitate, one ounce of sulphuric ether was poured; the mixture swelled up considerably. It was thrown upon a white paper filter. In the course of an hour and a half, a deep black liquid ran through, which weighed half an ounce. It had a strong ammoniacal smell, burned very readily, and left a bulky charcoal behind it. The matter remaining upon the filter had a frothy appearance; but, when dry, it was in the state of a very fine powder, and had lost much of its dark colour. It now weighed 4 drams. This powder was digested three times in caustic ammonia, and as often in alcohol. Both of these liquids acquired a dark-brown colour, and left the morphia in the state of a brownish-white powder, reduced to the weight of three drams. This powder was dissolved in 12 ounces of boiling alcohol. The filtered solution being set aside for 18 hours, deposited colourless, transparent crystals, consisting of double pyramids. These crystals weighed 75 gr. and consisted of morphia in a state of purity. The alcoholic solution being evaporated to two ounces, deposited one dram of morphia, similar to its state before its solution in the alcohol. When still further concentrated, 15 gr. of yellow-coloured morphia were obtained. The crystals of morphia thus obtained contained no traces of ammonia. 2. Properties of Morphia.-It crystallizes in double four-sided pyramids, whose bases are squares, or rectangles. Sometimes in prisms with trapedoizal bases. It dissolves in 82 times its weight of boiling water, and the solution on cooling deposits regular, colourless, transparent crystals. It is soluble in 36 times its weight of boiling alcohol, and in 42 times its weight of cold alcohol of 92°. It is soluble in eight times its weight of sulphuric ether. All these solutions change the infusion of Brazil wood to violet, and the tincture of rhubarb to brown. They have a bitter and peculiar astringent taste, and the saturated solutions of morphia in alcohol and ether, when rubbed upon the skin, leave a red mark. The following are the salts of morphia examined by Choulant. (1.) Sulphate of Morphia.-It crystallizes in prisms, dissolves in twice its weight of distilled water, and is composed of (2.) Nitrate of Morphia.-Needle-form crystals deposited in stars. Soluble in 14 times its weight of distilled water. Con (3.) Muriate of Morphia.-Feather-shaped crystals and needles. Soluble in 10 times its weight of distilled water. Constituents, (4.)-Acetate of Morphia.-Crystallizes in needles. Soluble in its own weight of water. Constituents, (5). Tartrate of Morphia.-Crystallizes in prisms. Soluble in thrice its weight of water. Constituents, (6.) Carbonate of Morphia.-Crystals short prisms. Soluble in four times its weight of water. Constituents, XVI. On the Equivalent Number for Morphia. From the numbers which I have annexed to the preceding analyses of Choulant, indicating the weight of the atoms of the acids, and the corresponding number for morphia, it is obvious that the analyses are very far from correct; for we obtain a peculiar number for morphia from each salt. These numbers are as follows : From the sulphate . nitrate. 9.009 12.150 5.132 The number from the carbonate differs so far from the rest that we must exclude it. It is obvious that the substance examined must either have been a mixture, or a subsalt. The mean deduced from the remaining five salts, gives us 8.268 for the weight of an atom of morphia. In the present state of the investigation, we may take 8-25 as an approximation to the weight of an atom of morphia; but in all probability it is not a very near one. Choulant's experiments must have been made upon too small a scale to expect accurate numerical results. ARTICLE XIII. Astronomical, Magnetical, and Meteorological Observations. By Col. Beaufoy, F.R.S. Bushey Heath, near Stanmore. Latitude 51° 37′ 42′′ North. Longitude West in time 1′ 20-7′′. Owing to the shortness of the days, evening observation discontinued. In taking the monthly mean of the observations, that on the morning of the 25th is rejected, being so much in excess, for which there was no apparent cause. |