THE completion of Dr. Thorpe's Dictionary, upon which both men of science and of practice may with truth congratulate him and his contributors, opens out the question how far such a work, however well done, can or cannot supply the needs at once of the layman, of the scientific man, and of the manufacturer. Perhaps this standard may be too high a one to apply to any single work, and yet I think that in many respects these three volumes will be found satisfactorily to fulfil the above requirements. That in some instances this cannot be said to be the case is not only not to be wondered at but almost to be expected, when we remember the extent of the ground covered, the complexity of the questions considered, and, above all, the difficulty which persons not actually engaged in the various industries experience in obtaining the latest details of new and improved methods and processes. In looking through this volume one is struck with the care which the editor has taken to carry out the condition that the articles on special manufactures ought to be written by scientific men who are themselves engaged in conducting the industry, rather than by those who can only look on those questions from outside. To give examples of this is easy. Take the article on Borax (Sodium Borate) written by Mr. E. L. Fleming. The reader will at once see, by comparing this with any descriptions of the process of preparing borax given in the text-books, that this article is full of data which have hitherto been either ignored or incorrectly given. Again “Sugar,” written by Messrs. Newlands, extending over twenty-two pages, is a typical case of descriptions of processes written by persons well acquainted with the details of the operations and able to describe them clearly, and, what is important, care has been taken to illustrate the article by excellent figures of plant. Closely connected with this subject, and also admirably treated by Mr. Heron, a practical authority, to whom we likewise owe an exhaustive article on saccharimetry not to be equalled in any work of the kind, is a description of starch manufacture, in which the newest processes are described and the construction of the most recent apparatus well shown. Then the articles, “Pottery” and “Porcelain,” written by Mr. Burton, of Wedgwoods, is another example of processes described by one who knows what he is writing about. Another remarkable instance of the same thing is that of the article, “Phosphorus,” by Dr. J. B. Readman. Hitherto the detail of phosphorus manufacture has been a mare clausum to the scientific world—and so well have the secrets of the trade been kept, that in no treatise, whether purely scientific or otherwise, have the particulars of the production of phosphorus been hitherto made known. Now for the first time we have, from the pen of one who was himself engaged in the industry, a complete description not only of the methods adopted for making both white and red phosphorus, but likewise the manufacturing details as to yield, which are invaluable. It seems that the explanation given in the books as to the preparation of this important element has been altogether wrong. It has been generally supposed that only so much suLphuric acid is added to the bone-phosphate as will form the acid phosphate, , and that this yields metaphosphate, , when heated to redness, so that when this latter is distilled with charcoal only two-thirds of the phosphorus are reduced, and one-third remains behind as tricalcium phosphate. This view turns out to be wholly incorrect. In practice enough sulphuric acid is added to convert all the lime present into sulphate, so that it is metaphosphoric acid, (HPO3), and not calcium metaphosphate, which on distillation with charcoal gives phosphorus, and the yield amounts to about 68 per cent, of the theoretical.
Dictionary of Applied Chemistry.
By Prof. T. E. Thorpe, assisted by eminent contributors. Vol. iii., completing the work. (London: Longmans, 1893.)
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