OF PRACTICAL ASSAYING, INTENDED FOR THE USE OF METALLURGISTS, CAPTAINS OF MINES, AND ASSAYERS WITH A COPIOUS TABLE, FOR THE PURPOSE OF ASCERTAINING IN ASSAYS BY JOHN MITCHELL, MEMBER OF THE CHEMICAL SOCIETY. LONDON: H. BAILLIERE, PUBLISHER, 219, REGENT STREET, FOREIGN BOOKSELLER TO THE ROYAL COLLEGE OF SURGEONS AND THE PARIS: J. B. BAILLIERE, LIBRAIRE DE L'ACADEMIE ROYALE DE MDCCCXLVI. Deration. Funo & 2.60 TRANSFERRED TO LONDON: Printed by Schulze & Co., 13, Poland Street. PREFACE. WHEN the rank our country holds among nations as regards her mining interest, is taken into consideration, it must be with all a matter of surprize that no work especially devoted to the elucidation of the processes to be employed in ascertaining the richness in metal of any sample of ore (that is, in other terms, its assay) has of late years appeared before the British Public. Indeed, the only work at present known in England is Berthier's "Traité des Essais par la Voie Sèche," which, for the mere purpose of inculcating the principles of assaying, has many disadvantages; not the least of which is its being written in a foreign tongue; and although a knowledge of French is now so very general, yet many parties are prevented from buying scientific works in that language on account of the difficulty of finding equivalents for the technicalities which must necessarily be employed. It is also a very large work, and one containing much matter which the assayer does not heed, matter relating to the composition of wood and coal ashes, furnace products, &c., which are more especially adapted for the metallurgist. These considerations, coupled with the paucity of any knowledge of assaying, excepting that confined to a very limited number of persons, induced the author of the following pages to turn a considerable amount of his attention to this subject, more especially as much difficulty was experienced in not having a suitable text-book for the use of his pupils. A portion of the following pages was drawn up as a Manual for such a purpose; but on consideration, it was thought the extension of such a work was so much needed, that it was determined to alter the original plan as far as was consistent with the complete carrying out the object in view, viz. the production of a Manual embodying information in every branch of assaying, either by the wet or the dry processes. The following is a sketch of the manner in which this is accomplished: the author having followed the excellent arrangement of Berthier as closely as possible, from whose work also much matter that suited these pages, and which it would have been useless to rewrite, has been inserted. Firstly, the Mechanical and Chemical Operations of Assaying are treated in full, inclusive of a description of the apparatus required, their mode of use, &c. Secondly, Furnaces, Fuel, and Crucibles, together with a description of the best Pyrometers and their applications. Thirdly, the Fluxes, their properties, preparation, use, &c. Fourthly, an Essay on the use of the Blow-pipe, and all its necessary appurtenances, as Fluxes, Supports, &c. Fifthly, the action of the Fluxes on some Mineral Substances. Sixthly, a method of discriminating many Minerals by means of the Blow-pipe, aided by a few tests by the humid method. Seventhly, the Humid Analysis of many Mineral Substances, their composition, locality, &c. (All the minerals mentioned in the three last heads comprehend such only as generally come under the notice of the assayer). Eighthly, the complete Assay of all the common Metals, in addition to which the Assay of Sulphur, Chromium, Arsenic, Heating Power of Fuel, &c. is fully discussed; and ninthly, and lastly, a copious table drawn up for the purpose of ascertaining in Assays of Gold and Silver the precise amount, in ounces, pennyweights, and grains, of Noble metal contained in a Ton of Ore from the assay of a given quantity. This table is the most complete and copious yet published. Not only has it been endeavoured to collect all that is generally known on the subject of Assaying, but many new facts have been added, and such matter entered into, that the success of an assay is rendered |