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145 



THURSDAY, JUNE 15, 1893. 



APPLIED CHEMISTRY. 



Dictionary of Applied Chemistry. By Prof. T. E. Thorpe, 

 F.R.S., assisted by eminent contributors. Vol. iii., 

 completing the work. (London: Longmans, 1893.) 



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 con- 

 sidered, 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 (Scdium 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, 

 e.xtending 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 ex- 

 cellent 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 writ- 

 ing about. Another remarkable instance of the same 

 thing is that of the article, " Phosphorus,'' by Dr. J. B. 

 Readman. Hitherto the detail of phosphorus manufac- 

 ture has been a viare 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 in- 

 dustry, a complete description not only of the methods 

 adopted for making both white and red phosphorus, but 

 NO. 12,33, VOL. 48] 



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, CaH4(P04)2, 

 and that this yields metaphosphate, Ca(P03)2,when heated 

 to redness, so that when this latter is distilled with char- 

 coal 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 Hme 

 present into sulphate, so that it is metaphosphoric acid, 

 (HPO3), and not calcium metaphosphate, which on dis- 

 tillation with charcoal gives phosphorus, and the yield 

 amounts to about 68 per cent, of the theoretical. 



In a notice like the present it is not possible to do 

 more than to run through a few of the most interesting 

 articles in alphabetical order. I take first that on Oils, by 

 Mr. A. H. Allen, of Sheffield, an authority on this some- 

 what difficult subject. No less than thirty-eight pages 

 are devoted to the description of fixed oils and fats, 

 especially with respect to their classification and identifi- 

 cation by analysis, in which the newest and most 

 improved methods are given. I fail, however, to find the 

 name of Chevreul mentioned, to whom chemistry owes 

 the first and still classical research on fats. Then I next 

 take " Oxalic Acid and the Oxalates," a short article by 

 the editor, whose valuable contributions, be it here said, 

 form no inconsiderable fraction of the total 1058 pages. 

 He has not stated the interesting fact quoted in the report 

 published by Drs. Schunck, Smith, and myself in 1862, 

 which, although ancient history, is still true, that from two 

 pounds of sawdust no less than one pound of crystallised 

 oxalic acid is obtained by Dale's process. Nor do I find 

 any mention of manganese oxalate, which is now a market- 

 able product, and is used as a drying agent for oils, and 

 has the advantage over the other " driers," inasmuch as 

 they colour the oil, whereas manganese oxalate can be 

 used so as to yield an almost colourless drying oil. 

 Omissions such as these are, as I have said, not to be 

 wondered at, and I quote them with the object of pointing 

 out that this Dictionary, admirable as it is, cannot replace 

 such sources of information on applied chemistry as the 

 journal of the Society of Chemical Industry, but that it 

 must rather be considered as an introduction to such a 

 mine of wealth as this journal — which I may call a child 

 of my own — contains, and to add, as I feel bound to do, 

 that some of the writers would have done well to refer 

 more fully to its twelve volumes before completing their 

 articles. 



Next comes " Oxygen," written by Dr. L. T. Thome, 

 of Brin's Oxygen Company, and here I may notice a 

 misprint on p. 83 — and say that such misprints are 

 singularly rare throughout the book, reflecting great credit 

 on both editor and printer — which has puzzled me. In 

 the description of Robbin's process a reference is given 

 P.J. [2] J. 436. I looked in vain through the Journal 

 fiir Praktische Chemie^dinA only after some time discovered 

 that P.J. should be Ph. (the Pharmaceutical Journal). 

 A more important error remains to be noticed in this 

 paragraph. How a mixture of 3 mols. of barium chloride 

 and I mol of potassium bichromate, on treatment with 



H 



