OF THF LYCEUM OF NATURAL HISTORY. CHEMICAL EXAMINATION of some Minerals, chiefly from America.* By THOMAS THOMSON, M. D. F. R. S. L. & E. &c. Professor of Chemistry, Glasgow. With Notes by JOHN TORREY, M. D. Professor of Chem. and Bot. in the University of the State of New-York. Read November 5, 1827. THE following analyses were made in my laboratory during the course of the years 1826 and 1827. A considerable number of them were conducted by myself; but a still greater number were entrusted to my practical pupils. Their analyses may be considered as precisely the same with my own, because the methods employed are mine, the reagents and apparatus are mine, and because I carefully superintend every step of the process, till the pupil has acquired sufficient practical skill to conduct an analysis with accuracy. The number of analyses was so great, that if I were to give a detailed account of each, I should have to write a treatise instead of a paper. It will shorten this essay very materially, if I premise a few observations on my methods of * A large proportion of these minerals was sent to Dr. Thomson by Mr. Nuttall and myself. At the request of Dr. Thomson, I have added a few notes of explanation respecting the localities, history, &c. of some of the specimens. J. T. analysis in the first place, and then satisfy myself with stating the general results of each particular analysis, without entering into any details. My methods were originally founded on a careful study of the analytical papers of Klaproth and Vauquelin. Their methods were a good deal improved, by repeating many of the excellent analyses given more lately to the public by Stromeyer and Berzelius. A careful examination of the properties of the various bodies usually found in minerals, naturally suggested new, or at least improved processes. But it is the perfection to which the atomic theory has been lately brought, which has conduced more than any thing else, to the accuracy introduced into the modern analyses of minerals. In choosing a specimen for analysis great attention is requisite; for unless the mineral be pure, or nearly so, the labour is thrown away. If possible, it should be in crystals, and every portion exhibiting the least trace of foreign matter should be rigidly excluded. Even with every attention to the purity of the specimen selected, the results obtained are frequently such, as to lead to the suspicion that foreign matter had existed in our mineral. In such cases it is of great importance to repeat the analysis upon a specimen from a different locality, and, if possible, from a different species of rock; for it is not likely that the same kind of foreign matter should exist in two minerals extracted from rocks of different species. Thus, if we were to analyse two amphiboles, the one from a calcareous rock, the other from a greenstone rock, though both might be impure, yet the particular impu rity would probably be different in each. We might expect a contamination of calcareous matter in the former, and of silica and alumina in the latter case. Stony minerals, as far as their chemical analysis is concerned, may be divided into three sets. 1. Those which are soluble in nitric or muriatic acid. 2. Those which, in order to dissolve in muriatic acid, must be heated to redness, with a mixture of thrice their weight of dry carbonate of soda. 3. Those which require to be heated with caustic potash, in order to render them soluble in muriatic acid. 1. The greater number of the minerals formerly confounded under the general name of zeolites, are readily soluble (if in sufficiently fine powder) in muriatic acid. These consist of various hydrous silicates, united together in very different proportions. Silicates of alumina, of lime, of iron, of potash, or of soda, are the most common of these bodies. a. I usually operate on 25 grs. or 30 grs. when the mineral contains much water. The mineral, previously reduced to a fine powder, is put into a flask, and digested on the sand bath with diluted muriatic acid till a solution is obtained. Great care must be taken to prevent any of the silica contained in the mineral from adhering to the inside of the flask. This is best done by agitation, which should be almost constant. And as soon as the mineral is dissolved, the whole contents of the flask should be poured into an open evaporating dish, before the silica begins to gelatinize. Should the silica from inadvertence be allowed to adhere to the inside of the flask, it cannot be washed out by water or acids. A little potashley, assisted by a gentle heat, will readily dissolve it. But great care must be taken not to act upon the glass flask. The acid solution is evaporated to dryness, and water acidulated with muriatic acid, is digested on the dry residue, till every thing is taken up except the silica; the whole is then carefully washed into a filter. The filtering paper which I use, is unsized printing paper, procured from the papermaker. Our paper, from the great diversity of materials employed in its manufacture, and from the process of bleaching the rags by means of chloride of |