APPARATUS, ETC. 385 REVIEWS. ALLEN’S COMMERCIAL ORGANIC ANALYSIS. Vol. V.: Tannins and the Analysis of Leather. By W. P. DREAPER. 1911. London : J. and A. Charchill. Price 21s. net. Remembering the painstaking work which distinguished the first edition of this well-known book, the perusal of the sections on Tannins and Leather Analysis has been one of disappointment to the writer. The author has failed to render himself familiar with much recent work, and as a compilation, the chapters must be pro- nounced uncritical and in places unreliable, and containing much obsolete and useless matter.In several cases work is incorrectly described, and in more than one is attributed to the wrong author. Such charges are not to be made lightly ; and, at the risk of being tedious, they386 REVIEWS must be supported by detailed instances.On the very first page the tannins as a class are characterised as ‘( notably soluble in ethyl acetate.” In fact, their solubility in this reagent is very varied, and in some cases almost nil, and this peculiarity has been used by Stiasny in the separation of different members of the group. Tannins are spoken of as 6‘ powerful reducing agents,” (‘ especially in alkaline solution,” while it is only under the last condition that they show any marked affinity for oxygen.On p. 7 gallotannic acid is mentioned as a glucoside, which is contrary to the modern view. Sumach-tannin is described as “possibly identical with gallotannic acid,” while Strauss and Schwendner have shown that this is not the case.Hemlock-tannin is stated to contain phloroglucol, which is incorrect. The tannin of horse-chestnut bark is spoken of as “chestnut tannin,” which is misleading, since the very important chestnut extract of commerce is made from the wood of the true Spanish chestnut, castanea vesca, which is not even mentioned in the table. The same remark is also to some extent true of ‘( ulmo-tannic acid,” since the LLulmo” bark of South America, which is now much used in tanning extract manufacture, is probably not a, true ulmus.On p. 8 the Stiasny formaldehyde test for catechol tannins is incorrectly given, and completely misunderstood. The Seyda test with gold chloride on the following page is merely the formation of colloidal gold, and the reaction is produced by any feeble reducing agent.On p. 14 the phloroglucol test with deal-shaving is stated in a note to be given also by catechol. Procter (“ Lab, Book,” p. 152) has shown that this is an error, though a blue violet is given by resorcinol, which is often present in commercial catechol ; and this correction is quoted by the author himself on p. 54 without remark ! Schiffs reputed syntheses of digallic acid, both with phosphorous oxychloride and with arsenic acid, are now generally discredited, as it has been found impossible to free the product from the reagents without reconverting it into gallic acid.Hunt’s attempted synthesis with monobromo-proto-catechuic acid and potassium gallate (which is mentioned on p. 17 without the name of its author) has never been success- fully repeated, though tried by Schiff, and is now assumed to have been an error.The formula for ellagic acid, which on pp. 19 and 23 is attributed to Nierenstein, was proposed long ago by Graebe, and proved by Kostanecky, Perkin, Herzig, and others. On pp. 29 and 30 all the information as to the chemistry of catechins is more or less obsolete ; the work of A“. G. Perkin is not quoted, and the constitution according to Kostanecky is not given, though this is one of the few formula in the chemistry of the tannins which deserves credit.On p. 31 chestnut wood extract is said to contain 14 to 20 per cent. of tannin, though 30 per cent. is nearer the modern standard, and this criticism applies to nearly all the tabular information given on the strength of tanning materials, the analyses quoted being mostly by obsolete methods giving far too low results.In fact, the information on tanning materials, occupying pp. 31 to 55, is very sketchy and incomplete; for instance, oak-wood extract, which is now one of the most important materials, is mentioned only in a table of 1883 attributed to Simand, which gives the total tannin as 14.47, and the part of this soluble in cold water ae 15-09 I On pp. 42 and 43 qualitative tables attributed to Procter are really due toREVIEWS 387 Andreasch, and no mention is made of the fact that they are only applicable to alcoholic solutions, though the original source is referred to on p.55 with apparently no idea that the tables are identical with those given. No mention is made of the frequent use of extract of mangrove bark as adulterant of quebracho, nor of methods for its detection.The modern quantitative methods are correctly given, mostly in the words of the official prescriptions of the I.A.L.T.C. and the A.L.C.A., but are not critically discussed; and a good deal of space is occupied by the description of antiquated processes, most of which are known to give incorrect or unreliable results.In the section on the analysis of leather the von Schroeder method of glucose estimation is very briefly described, but the necessary glucose table is omitted both there and in the section on glucose estimation in tanning materials, and in place of it a single factor is given. No mention is made of the ordinary volumetric method, which, if carried out with proper precautions, gives results of considerable accuracy, and is very useful as a rapid process of preliminary investigation, and will usually decide whether or not artificial loading has taken place.Sucrose is now sometimes used in place of glucose, and, of course, is not estimated by either process without previous inversion. No mention is made of Fahrion’s method of deter- mining a tannage value by boiling with water, and in the formula for calculating hide-substance from the Kjeldahl determination of nitrogen, + is written instead of x , Further remarks seem unnecessary.HENRY R. PROCTER. DYES AND COLOURING MATTERS, DYESTUFFS OF GROUPS 6 TO 12, COLOURINU MATTERS By J. T. A very valuable feature of this fourth edition of Allen’s well-known treatise is that the analytical examination of the various organic products under consideration is pre- ceded by thoroughly upto-date descriptions of the systematic chemistry of these materials, each section being dealt with by competent experts.In the chapter on dyes and colouring matters a brief r6sum6 is given of the modern development of artificial colouring matters and of the relations of dyes to the textile fibres.A con- sideration of the nitro-, nitroso-, and isonitroso-colouring matters is included in this section, which also deals very fully with the important azo-dyes. Very comprehensive tables are given, showing the mode of formation and the specificreactions of the azo- dyes. In some instances, however, the abbreviations employed have almost ceased to be intelligible.For example, Fast Acid Scarlet (4)SO,Na.CI,H,. N2(6). C,,H,.OH is said to be obtained from beta-acid, and Acid Ponceau from a and y naphthylamines (sic). There are also a few orthographical errors, such as ‘ I unsoluble,” phenatidine,” and ‘( dinitrosoresorcnol.” The remaining synthetic dyes are arranged in seven groups (groups 6 to 12 inclusive), a separate section being devoted to indigo.The prevailing views on the constitution of the di- and tri-phenylmethane colouring matters are critically examined and the properties of the principal commercial dyes of these series are arranged in tabular form. The azine, azonium, quinoline, and acridine dyes are similarly treated. OF NATURAL ORIUIN AND ANALYSIS OF COLOURINU MATERIALS.HEWITT.388 REVIEWS Indigo is classified under colouring matters of natural origin, and, possibly on this account, very little space is devoted to the important subject of synthetic indigo. The estimation of indigotin is, however, dealt with in greater detail, especially as regards the oxidation and reduction tests, reference being made to such modern developments as the production of indigotintetrasulphonic acid and the reduction of sulphonated indigotin with titanous chloride.A survey of such natural dyestuffs as logwood, fustic, turmeric, cochineal and the red woods is followed by a, chapter on the analysis of colouring materials, giving methods for the examination of commercial colouring matters and their detection of the dyed fibres.The detailed information contained in a very concise form in this section of the treatise should prove of the greatest service to analysts called upon to examine fabrics dyed with the colouring matters employed in modern practice. G. T. MORGAN. FOODS : THEIR ORIGIN, COMPOSITION, AND MANUFACTURE. By WILLIAM TIBBLES, M.D., LL.D., etc. London : Baillidre, Tindall and Cox.1912, Price 18s. net. This work is a veritable encylopzedia of foods, and of substances used in the preparation of food. I t would, indeed, be difficult to mention any food material, from the most important and necessary to the most trivial condiment or colouring matter, which does not here find a place and adequate description. The hard-worked scientific man must always feel a sense of gratitude towards his more leisured confrere, when that leisure is employed in the collection and compila- tion of the widespread information which to-day forms so important an adjunct to the analytical armoury.I n order that such a work should fulfil a really helpful and useful purpose, it is necessary that the author should possess sufficient scientific insight to enable him to judge of the value of the different sources of information at his disposal and sufficient diserimination to sift them adequately.When these dicta are applied to the work under review, one is compelled to admit that they are fulfilled. The selection of authorities is excellent, and the “drawing from opposing authorities the pith of their knowledge,” described in the preface by the author as It is almost unnecessary to say that no man can be an authority on all branches of the widely diverse subjects here presented, nor does it seem that the author makes any special claim to have any special knowledge of any one of them. It is, therefore, inevitable that the expert in any of these subjects may have cause to find fault with Borne of the statements, etc., made, particularly if his pet theories happen to be omitted, or inadequately mentioned.I n actual fact there are numerous errors, but these do not militate against the intrinsic value of the work. The author is happiest in those sections which deal with processes which are not closely interwoven with trade secrets and methods, for which one wili look in vain in this, as in any other book ; but in the general composition of the final products, and in trade descriptions of these products, there is much sure ground.One notes with pleasure the great use which has been made of the invaluable bulletins of the U.S. Department of Agriculture, and the large collection of these will be useful to many. I t would be quite impossible to deal with the various chapters source of delight,” has, in nearly all cases, been happily carried out.REVIEWS 389 one by one, as the before-mentioned diversity of subject-matter precludes personal criticism as much as it precludes comprehensive expert treatment in its composition.Part I. deals with the (6 chemical constitution of foods and the classification and character of their proximate principles.” The matter dealing with this intricate subject is well put together, and displays knowledge of the latest work, though some references to the conclusions of older investigators might well have been omitted in view of more reeent findings.The chemical presentation is somewhat crude in expression in many cases and this is true of the work as a whole, though there is never any real doubt as to the meaning intended.There are some curious and oft repeated errors which are difficult to understand, such as the description of ‘‘ cholesterin ” as a nitrogenous fat, though in its proper place it is correctly described. “Protagon ” is also spoken of as a separate entity, The carbohydrates are fully dealt with, and the section has been compiled from reliable sources.In the chapters on the Mammalia, Pisces, and Aves, the author is probably at his best, as the scientific descriptions and classification are from excellent authorities, and are presented in a concise and thorough manner, with full details as to distribu- tion on the earth’s surface, and to the use made of them as food. There is also EL useful chapter on meat inspection and regulations, and on the composition of meat as eaten and its digestibility. The properties of meat extracts, soups, etc., are given, and from the remarks appended there is evidently considerable personal knowledge of these aliments.The care which the author has expended in the sifting of available data is nowhere better seen than in the sections dealing with such debatable matters as milk and milk products.In addition to the general consideration of the subject, he has succeeded in disentangling from the masses of conflicting evidence which have gathered round such points as the influences which affect the composition of milk, the effect of feeding, period of lactation, etc., the more vital and probably correct, conclusions. One notices, however, with a slight feeling of amusement, the list of constituents of milk which is given, and which, if all had to be determined, would render the analysis a rather titanic task, very different from the usual (( total solids and fat ” beyond which few analysts appear to venture.The bacteriology of milk-souring is, on the other hand, very inadequately de- scribed, and the latest work is not mentioned. Under milk preparations, cheese, both in its aspects of manufacture and subse- quent ripening, is adequately dealt with, and nearly every milk preparation known finds notice, and, in general, correctly, except in the case of condensed milk, for which only one or two quite out-of-date methods are referred to. The chapters on Cereals, Vegetables, and Fruits are excellent and most complete, the botanical descriptions being quite reliable.Full details are given of the preser- vation of fruit, and it is to be wished that the description of ‘(jam ” manufacture was applicable to more of our jams than it can possibly be. The Public Analyst will be fully in accord with the author in his remarks under ((What is jam?” A compre- hensive list of colouring matters is appended, and it is noticeable that some common errors in regard to these are avoided.Even in such a difficult subject as that of oils, the information is reliable and390 REVIEWS trustworthy, though some of the processes stated to be used are somewhat obsolete. A few of the trade descriptions in this section are not quite correct, such as the information that ‘( nucoline ” is palm-kernel oil. The other chapters which deal with tea, coffee, chocolate, spices, condiments, sugar, honey, confectionery, wines, spirits, and malt liquors may be passed over without comment.The only serious mistake that the author has made is the inclusion of analytical methods, as in nearly all cases these are hopelessly impossible or badly described. As they are quite out of place, it would have been much better if they had been omitted.In spite of the condensed nature of the book, the matter is always in most readable form, and the proof-reading, with a few exceptions, carefully done. There is not the least doubt that this work would be of much assistance to the general analyst as a concise book of reference. C. REVIS. VOLUMETRIC ANALYSIS FOR STUDENTS OF PHARMACEUTICAL AND GENERAL CHEMISTRY.By C. H. HAMPSHIRE, B.Sc., A.I.C. Pp. vi + 104. London : J. and A, Churchill. 1912. Price 3s. 6d. net. As its title indicates, this book is not intended for the use of analysts, but for the instruction of students, particularly pharmaceutical students, and it must be judged accordingly. For example, anyone who attempted to use this book as a book of reference, and followed the directions given on p.98 for the analysis of a mixture of boric acid and borax, would soon find himself in difficulties, unless he already knew all that this book has to teach. But the student who has steadily worked through the book up to this point would be in no difficulty, for in earlier pages the principles underlying mixed titration are clearly explained; The whole book is a model of lucidity, and one can only regret that the author did not suppress some redundant paragraphs, such as the titration of sodium bicarbonate after that of potassium carbonate had been described, and so have found room for a short description of methods of standardising apparatus. Criticism on many points which a t first sight seem to invite criticism, is silenced by the reflection that the author’s students are mainly concerned to determine whether certain drugs comply with the requirements of a Pharmacopoeia which, in addition to other demerits, is fourteen years old. There are very few misprints, but presumably the direction on p. 23 to determine the strength of limewater by titrating 25 C.C. with I ( normal ” acid must be reckoned as one, and one would like to believe that the word 6‘ better ” on p. 6, line 4, was a misprint for ‘‘ necessary.” The former is scarcely a strong enough word with which to back a recommendation to make use of a desiccator for cooling ignited sodium carbonate, which is to be the ultimate standard in all the acidimetric and alkalimetric work which is to follow. G. CECIL JONES.