XLIII. Description of a portable Mineralogical Laboratory. By FREDRICK ACCÙM, M.R.I.A. F.L.S. Operative Chemist, and Lecturer on Chemistry and on Mineralogy and Pharmacy. SINCE chemistry has in a manner changed its appearance, since its means of analysis have been increased, and since the instruments of research have acquired their present high degree of perfection, new paths for exploring the productions of nature have been opened, the art of experimenting has been simplified, and become more familiar and easy. Most of the operations of chemical science which formerly demanded a regular laboratory, may now be performed on a small scale, with more perspicuity and expedition by the help of such instruments as most persons can command. Thus, however varied the objects of experiment may be, and however numerous and different the products to be obtained may appear, the most costly materials may be used at a trifling expense in such pursuits. The operator is enabled to observe the gradual changes of each process with more facility and speed in the small way, than in the large; it is in his power to urge, or to retard readily the operation at pleasure, and to ascertain each step of the experiment, from beginning to end. Such advantages will be valued properly by those who know that the most experienced and most attentive chemist meets with frequent accidents, by which both the vessels and the products of the operations are lost, because he has it not in his power to ascertain the nature of the results as occasion may require. It is thus also that, among the furnaces of the laboratory, many appearances often pass away unnoticed, which are readily observed when the same operation is performed on the table, and under the immediate eye of the experimenter. Besides, most of those investigations which in the large way require several days' labour, can on a small scale be finished in a few hours. The heat of the most violent furnaces may instantly be produced by a stream of air, passing from a blow-pipe bladder, on a piece of ignited charcoal, or through the flame of a candle or spirit lamp. By means of the brilliant flame of the lamp furnace, a vast number of chemical operations may be performed, which thirty years ago would have required a series of complex furnaces. All the processes of digestion, the sublimation of salts, the solutions of earthy and Vol. 37. No. 156, April 1811. Q metallic metallic bodies, the concentration of saline and other liquids, the desulphurations of metallic ores, the multifarious processes of distillation by the naked fire, or the sand-bath; the production of gases with the pneumatic apparatus; and even the fusion of earthy fossils with alkalies for analysis, may be accomplished, on the table, by means of this apparatus alone, with much neatness and at a trifling expense. And as the knowledge of chemistry is founded on practical research, we cannot hope to pursue the study of it with advantage, without performing such processes as verify most of the capital generalities of the science, and also such as reasoning, analogy, and a laudable desire of experimenting, never fail to suggest to those whose taste and talents lead them that way. This mode of study is the more essential, because, in the most common operations of experimental chemistry, a vast number of small facts occur, which are not mentioned in books, but are essential to be known: if they were described as often as they present themselves in practice, a great loss of time would follow, because they are too numerous and too minute, and no advantage would be gained in perspicuity. It is the knowledge of these facts which distinguishes the expert operator from the bungler, and this knowledge can only be acquired by actual practice or manual application; and not from reading, nor public lectures, or other means. To give effect to operative researches, the most celebrated philosophers have furnished collections of instruments of experiment to facilitate the attainment of practical knowledge. The bare mentioning of some of them will be a sufficient proof of what has been stated. The blow-pipe apparatus of Bergman; the pocket laboratory of Cronstedt; the travelling chest of chemical re-agents of Göetling; the œconomical laboratory of Guyton Morveau; the mineralogical chest for the analysis of soils and manures, lately recommended by the illustrious Professor of the Royal Institution; and many others, are too well known to render further observations concerning the utility of the above statement necessary. Emboldened by these proceedings, I presume it cannot he thought foreign to the views of a journal which professes to be consecrated to the diffusion of chemical knowledge, to lay before the public a sketch of a Portable Mineralogical Laboratory, which is designed chiefly for those cultivators of mineralogical science, whose means of in Davy's Memoir on the Analysis of Soils. dulgence dulgence in experimental pursuits are limited, or who have neither leisure nor inclination to operate in the laboratory. The approbation which this portable collection of instruments has met with among the mineralogical public, and the sanction which I have received concerning it from different quarters, give me reason to believe it has proved useful; indeed I feel no hesitation to say, that the assistance which this collection of instruments and tests is capable of rendering to those who are not without some tincture of science, may promote the diffusion of knowledge and accelerate the progress of the student. It may enable the young mineralogical chemist to acquire readily such information concerning a mineral he may meet with in his travels, or elsewhere, as is sufficient to determine the uses to which the substance may be applied. And it is from a want of mineralogical inquiries, particularly among men of landed property, that useful minerals have often been overlooked; and many valuable products might pro-. bably be discovered in situations where they are least expected by landlord or tenant; because a general knowledge of the composition of minerals (or, to speak more correctly, what a body contains, and not how much,) is usually sufficient to direct their application to beneficial purposes. The Contents of the Mineralogical Laboratory are the following: CHEMICAL APPARATUS AND INSTRUMENTS. A lamp-furnace with Argand's lamp. Fig. 1. A balance, so constructed as allows it to be used hydrostatically, with accurate sets of weights. Fig. 2. Crucibles; of silver, porcelain biscut, and black lead. Figs. 3. 3. 3. 3. &c. A spirit-lamp. Fig. 4. A magnetic needle and stand. Fig. 5. An assortment of flat-bottomed evaporating basons of porcelain biscuit *. A blow-pipe (Fig. 6.)-A blow-pipe forceps entirely made of platina, a blow-pipe spoon, and platina foil. Watch glasses in sizes for evaporating small quantities of fluids. A copper sand-bath to fit the Argand's lamp. An apparatus for drying precipitates at certain temperatures, and also for evaporating fluids by steam. Fig. 7. ✦ The articles named without a figure of reference, cannot be seen in the perspective drawing of the chest. Q 2 A hand A hand mortar of Wedgwood's ware. Fig. 8. Glass funnels in sizes. Fig. 9. A cubic inch and ounce avoirdupoise measure. Fig. 10. Glass retorts and receivers. Fig. 11. Cylindrical glass tubes, for observing the changes produced in small quantities of fluids, by tests, &c. An iron ladle for roasting ores, &c. A steel anvil and hammer. A collection of matrasses, flasks, and assay jars, in sorts and sizes, for effecting solutions, digestions, &c. Fig. 12. A steel graver for examining the degrees of hardness of minerals. Chemical tongs, for removing crucibles out of the fire. A levigating mortar. Fig. 13. Glass rods for stirring corrosive fluids. A piece of hardened steel-Pieces of well-burnt charcoalA blow-pipe candle-Phials of all sorts-Unsized filtering paper-Strips of bladder for luting, and sundry other small articles. RE-AGENTS, TESTS, AND CHEMICAL PREPARATIONS. A person provided with such an assortment of instruments, tests, &c. may perform the analysis of any ore, earth, or other substance of the mineral kingdom. He may perhaps occasionally want a few other articles which are not contained in the chest ; but all these may easily and instantly be prepared; and others, such as the common or impure acids and alkalies of commerce, are to be had every where. All the instruments and bottles are arranged in such a manner that they may be seen at one view when the chest is open, and they are so packed that they may readily be taken out; and, when replaced, fit in such a way, that the whole, when the chest is locked, may be turned upside down without risk of receiving injury. Compton-Street, Soho, March 1, 1811. FREDRICK ACCUM. XLIV. Observations and Experiments concerning Mr. Davy's Hypothesis of Electro-chemical Affinity.-By M. DONOVAN, Esq. [Concluded from p. 233.] WHEN water is decomposed by means of metallic wires, which have an affinity for oxygen, the wire conveying po sitive electricity becomes oxidated. When a platina wire is employed, it does not oxidate, But by the hypothesis the union ought to take place; for the platina, naturally positive, has its energy considerably exalted, and consequently should unite with as much force to negative oxygen as any other metal under the same circumstances. The matter is simply thus: The cause of combination is attraction, the cause of attraction is existence in differently electric states: the more energetic these states are, the more violent is the attraction. Mr. Davy's words on this part of the subject are: "As the chemical attraction between two bodies seems to be destroyed by giving one of them an electric state different from that which it naturally possesses, that is, by bringing it artificially into a state similar to the other, so it may be increased by exalting its natural energy. Thus, while zinc, one of the most oxidable of the metals, is incapable of combining with oxygen when negatively electrified in the circuit, even by a feeble power; silver, one of the least oxidable, easily unites to it when positively electrified; and the same thing may be said of other metals." In the instance present, the oxygen is in the negative state, the platina is strongly positive, and precisely in the same circumstances as the silver in Mr. Davy's instance. Why then do they not combine with violence* ? It In the Philosophical Magazine, vol. xxxii. p. 88, we find the following, from a Correspondent: "Mr. Davy showed, by a refined application of his principles, that, in the decomposition of a neutral salt in solution, the order of the arrangement Q3 varies. |