1548), or by Whitney (Journ. Am. Chem. Soc., 1903, xxv., 394) or Cribb (The Analyst, 1905, xxx., 232), all of whom give experimental evidence to show that rusting takes place rapidly in the absence of carbonic acid, provided liquid water and oxygen are present. The experiment of Dunstan and his co-workers was so carefully carried out that there seems to be no doubt that if carbonic acid plays any role whatever it is an unimportant one, and that rusting can go on with extreme rapidity in its absence.

In order to confirm this conclusion, the following experiment was made by the writer :

The Jena glass flasks A, B, and the beaker c, shown in Fig. 1, were nearly filled with freshly distilled water, and boiled vigorously for one half-hour. While the boiling was still proceeding bright polished strips of charcoal iron and steel were slipped into flasks A and B, and the rubber stoppers, which had been previously cleaned by prolonged boiling in pure water, tightly inserted. After boiling for fifteen minutes longer the clamp at the end of tube D was opened for a moment, and the back pressure allowed to drive any last traces of air from the tube. After tightly closing the clamp again, the lamps under flasks A and B were removed, while the water in c was still kept boiling. Boiled water immediately sucked back until the whole apparatus was completely filled, no trace of air being present. At all events, no slightest trace of rust appeared on the bright metal strips when kept indefinitely under this boiled water. Pure oxygen from a cylinder was now washed perfectly free from last traces of carbonic acid by passing the gas through a train of wash-bottles containing caustic potash, barium hydroxide, and lime water. allowing this carefully purified oxygen to enter at D and bubble through the system of flasks, rust appeared on the bright metal surfaces in five minutes or less, and in one hour had become deep and heavy. The action, just as in Dunstan s experiments, did not take place evenly all over the surface, but in patches, which had the appearance of a more or less regular pattern following the physical structure of the metal. This experiments has been frequently repeated, with every possible precaution to avoid the entrance of even the smallest trace of carbonic acid. On numerous occasions a few drops of phenolphthalein indicator was added to the boiling water in the three flasks, and invariably a pink colour developed, proceeding from the metallic surfaces. This effect will be discussed at length further on, and is mentioned at this place as contributory evidence that carbonic acid is not necessarily present, as Moody believes, before any reaction between iron, water, and Oxygen can take place.

On

to last traces, it is easily shown that the hydrogen ions which would be supplied by a minute quantity of carbonic acid are of no more importance than the hydrogen ions supplied by the normal dissociation of pure water, and that the assumption that carbonic acid must be present is quite unnecessary. Whitney (Journ. Am. Chem. Soc., 1903, XXV., 397) shows this very clearly in the following paragraph:

"Assuming the laws of Henry and Dalton to apply to the solubility of the pure gas under ordinary pressure is one solubility of carbonic acid gas in water, also that the volume for one volume of water (which is correct at 15°C.), and, finally, that the normal content of carbonic acid in the atmosphere is 2 parts in 10,000 by volume, we should expect water in equilibrium with air containing this concentration of carbonic acid to contain 0.0002 volume carbon dioxide per volume of water. This corresponds to a concentration of the carbonic acid equal to o'oooor mol. per litre, or o'00002 normal. From the dissociation constant 3040 × 10-10 determined by Walker (Zeit. Phys. Chem., 1900, xxxii., 137), it follows that the first hydrogen of the acid is 16 per cent dissociated at this concentration. From this it follows that 10,000,000 litres of water containing carbonic acid in equilibrium with ordinary air at 15° contains 16 grms. of hydrogen ions, or only sixteen times as many as perfectly pure water contains. At the boiling temperature the carbon dioxide dissolved would probably yield a concentration of hydrogen ions even less than in pure water, for not only is the solubility of the gas greatly diminished, but the dissociation of water is greatly increased by rise of temperature. Moreover, the distilling water would rapidly reduce the concentration of any carbonic acid capable of dissolving in water at 100" C."

Moody prepared an apparatus in which the presence or subsequent entrance of even the smallest traces of carbonic acid was elaborately guarded against. The apparatus was constructed entirely of glass, and was arranged in such a manner that polished cylinders of almost pure soft Swedish iron could be subjected to the action of water, and air absolutely free from carbonic acid. Even with the very pure iron and with water which was undoubtedly rendered slightly alkaline by its intimate contact with a large surface of ordinary glass, Moody observed a slight amount of corrosion taking place on his bright iron surfaces. Still convinced, however, that the presence of carbonic acid was necessary before the slightest rusting effect could be produced, and believing that in some unknown manner an infinitesimal amount of this substance had eluded his vigilance, Moody began again with a new and quite extraordinary precaution. Before the bent tube, which contained the polished specimen of iron was fused into its solution of chromic acid which just covered the iron. When the apparatus had been swept with air free from carbonic acid for three weeks, water was distilled through the tube containing the specimen until the chromic acid was all washed away. After this, as well as the added precaution of covering the ends of the iron cylinders with wax to prevent contact with the glass (as an interaction between glass and iron appeared also to cause corrosion even if no carbonic acid was present), the experiment was finally a complete success. In one case a current of air was passed through the apparatus for five weeks without even one speck of rust appearing.

In

It may be doubted whether it is possible to boil out all carbonic acid fron the water contained in the apparatus shown in Fig. 1. Granting that this is the case in regard

If Moody's experiment could be accepted as final, we must conclude that in an atmosphere that did not, like that of this earth, contain about o'04 per cent of carbonic acid, the rusting of iron would be an unknown phenomenon.

It happens, however, that a recent observation of the writer explains the negative result obtained by Moody, without any reference whatsoever to the carbonic acid theory of rusting. It has long been known that rusting is inhibited, and that polished iron will remain bright indefinitely in alkaline solutions, provided they are suffi ciently concentrated. This is also true of all solutions of

CHEMICAL NEWS,

Jan. 1, 1909

salts of strong bases and weak acids which hydrolyse to an alkaline reaction (Zeit. Elektrochemie, 1903, ix., 446). This fact has been eagerly seized upon by the adherents of the three theories, as it can be made to fit in more or less well with them all. Thus, alkalis absorb carbonic dioxide, and therefore carbonic acid is prevented from carrying on its work of destruction. The added fact that fully saturated bicarbonate of soda also provides full protection to iron, even in fairly dilute solution, which would seem to be a stumbling block, has not shaken the faith of the devout believers in the carbonic acid theory.

a

The adherents of the peroxide theory claim that iron cannot rust unless hydrogen peroxide is formed as transition step in the reactions. As hydrogen peroxide is more or less unstable in alkaline solutions it is claimed that iron should not rust when immersed in them. The added fact that the rusting of iron is actually accelerated by solutions of potassium iodide, iodine, dilute potassium permanganate, and other substances which also destroy hydrogen peroxide, must apparently be accepted as an exception which proves the rule. The theory of electrolysis alone finds no difficulty in appropriating the facts of the alkali inhibition of oxidation. The full discussion of this point, however, must be postponed to a later portion of

this Bulletin.

As far as the writer is aware, Dunstan and his coworkers were the first to make use in a theoretical discussion of the fact that solutions of chromic acid, potassium chromate, and potassium bichromate exercise a complete protection from rust to the surfaces of iron specimens immersed in them. It is probable, however, that the protective power of the chromates and some other oxidising agents has been known, and to some extent made use of, in a practical way for a long time past (Trans. Am. Chem. Soc. Eng., 1894, xvi., 384). Wood stated in 1894 that a few substances, such as red-lead, pyrolusite, the bichromate of potash, and chromate of lead, were gradually coming into use for anti-corrosive paint compounds, and that their future use for this purpose was assured. This peculiarity of the chromates was interpreted by Dunstan as furnishing a proof of the peroxide theory, as it is well known that hydrogen peroxide is destroyed by chromic acid and its salts.

The writer has gone a step further, and observed that the protection afforded by chromic acid and its salts differs from that of the alkalis in that the passivity is in a sense acquired by the surface of the iron, and lasts for long periods, although the chromated specimens may have been washed with all possible care, and even wiped with a cloth. In the writer's experiments all chromating has usually been done by immersing polished specimens of iron and steel in a strong solution of potassium bichromate for a number of hours, generally over-night. Steel-wire nails treated in this way have been kept under water in vessels open to the contact of air and carbonic acid for many weeks without developing the slightest speck of rust or tarnish on their polished surfaces. In addition to this, polished specimens which have been chromated have been kept in moist air for weeks at a time without losing their passive condition. This astonishing phenomenon is so easily and quickly demonstrated by any one who cares to make a trial of it that it is not necessary in this place to include evidence to support the statement made above. The subject will be taken up in detail later on, and it is only mentioned here to show that Moody's experiment does not prove that the presence of carbonic acid is necessary before iron can rust. It must, of course, be admitted that the presence of hydrogen ions will hasten the corrosion of iron, and therefore the presence of a small amount of carbonic acid plays a minor rôle. The point that is made is that carbonic acid is not necessary, and that rusting can go on with extreme rapidity without it. If Moody had used pure oxygen instead of air he would undoubtedly have rusted his specimens in spite of their having been first chromated.

(To be continued).

NOTICES OF BOOKS.

II

A Treatise on Colour Manufacture. By GEORGE ZERR and Dr. R. RÜBENCAMP. Authorised English Edition by Dr. CHARLES MAYER. London: Charles Griffin and Co., Ltd. 1908.

THE German edition of this work was a book whose merits were immediately recognised, and one which met with much success; no doubt the English version will be equally appreciated, for though small alterations have been made, in the main it reproduces very faithfully the good features of the original. The different colouring matters are classified according to a convenient system, and each individual substance is given thorough treatment, some notes being occasionally added by the translator. A short summary is given of the coal-tar colours, and also some account of the uses of colours, which, however, is perhaps too much condensed to be of any practical good to the specialist. It is unfortunate that some very important recent advances, as in the analyses of lake pigments, are not described in the text, although in many cases the translator calls attention in a footnote to books and articles which may be consulted for the most recent

information.

Technical Methods of Chemical Analysis. Edited by GEORGE LUNGE, Ph.D., Dr.Ing. English Translation Edited by CHARLES ALEXANDER KEANE, D.Sc., Ph.D. Volume I., Parts I. and II. London: Gurney and Jackson. 1908.

THE English translation of this standard work on chemical analysis has been prepared from the second German edition, issued in 1904, and in many respects it must be regarded as a unique production. Each section, which was written by an expert in the first case, and represented the last word on analytical practice in Germany, has again been revised by an expert who has a special knowledge of the conditions of English manufacture where they differ from those which hold in Germany, and of the requirements of English chemists. The references to literature have been altered so that English books and articles are substituted for German, and where necessary the text has been brought up to date by Prof. Lunge and the English editor. The treatise fulfils a double purpose, being both a work of reference, summarising all well-established methods of analysing the raw materials, intermediate, and final products of the different industries, and also a practical laboratory guide describing the performance of the most satisfactory methods in the case of each substance. Volume I. has been issued in two parts, which contain, firstly, a complete introduction to chemical analysis, discussing all the methods employed with full details of the operations with which the chemist should be familiar. In addition many important groups of industries are treated, including the manufacture of acids, salt-cake, sodium carbonate, clay, glass, &c., while the analyses of air, water, sewage, soils are among the subjects treated in the second part,

Catalogue of Balances and Weights. London: F. E. Becker and Co. (W. and J. George, Ltd., successors). 1908.

THIS new balance catalogue is so excellently illustrated, and all the apparatus enumerated in it is described with such careful attention to every important detail, that no customer need entertain any doubt about the wisdom of ordering an article without having actually seen and handled it. The firm is renowned for the reliability and good finish of the instruments they put upon the market, and their prices must be acknowledged to be surprisingly low in some cases, especially when it is remembered that the name Becker is a guarantee of accuracy and good wearing properties. Various forms of specific gravity and

Catalogue of Apparatus for Chemical Lecture Experiments. London: A. Gallenkamp and Co., Ltd. 1908. THIS catalogue of apparatus for chemical lecture experi ments contains a price list of the whole range of Hofmann's and Newth's lecture apparatus with some valuable additions, and full descriptions are given of some of the instruments with directions for their manipulation. The time of the chemical lecturer or demonstrator will be much economised by the use of some of this apparatus, which is comparatively inexpensive, while sometimes troublesome to fit up from the ordinary laboratory stores. Attention must be called to the description of an optical lantern for horizontal and vertical projection, which would appear to be a thoroughly satisfactory instrument.

A Scheme for the Promotion of Scientific Research. By WALTER B. PRIEST. Second Edition. London: Stevens and Sons, Ltd. 1908.

THE second edition of this book is a reprint of the first, except that it contains scme fuller explanations and details, more especially of the question of assessment in the author's scheme for endowing scientific research. The plan seems workable, and in view of the excellence of the object which it aims at promoting, it would perhaps be invidious to lay too much stress on obvious defects and difficulties which are chiefly concerned with the assessment of the grants to be made. The author regards discoveries by which the mortality arising from various diseases may be lowered as deserving special attention and most liberal recognition, but the scheme might easily be extended to other fields of research. The procedure recommended is based upon the Patents Act of 1883, sections and sub-sections of which are quoted in an appendix. The author writes with moderation, and it seems probable that the adoption of his scheme would give an impetus to scientific research, and thus benefit civilisation.

Cours de Chimie Inorganique.

("Course of Inorganic Chemistry"). By FRED. SWARTS. Paris: A. Hermann. 1908.

THIS book occupies an intermediate position between those text-books which are rigidly divided into two partstheoretical and descriptive-and the more modern ones in which the treatment corresponds to the heuristic oral method of teaching, and theories are only suggested to explain facts which have already been observed or studied. Thus it belongs to the old type in that in a general introduction the atomic and other fundamental theories are discussed, while descriptions of the properties, preparation, &c., of each individual element follows. But, on the other hand, throughout the descriptive part are to be found discussions of the theoretical aspects of the various phenomena considered. The book is based upon the course of chemistry for engineering students at the University of Gand, and is thus not intended for the use of young beginners. Although it is perhaps not a work which a student could be advised to read straight through, it is in many ways not unsuitable for him if he has the advantage of having a competent teacher to decide in what order the chapters are to be read. The student will find the frequent heavy type and the short paragraphs employed are helpful, and, on the whole, he will be able to gain from the book a very fair notion of descriptive chemistry, including some metallurgy and industrial processes. One chapter is given to thermochemistry and is a good feature, but a serious defect is the omission of all allusion to the Periodic System. is now generally recognised that an outline of the main features of the system give interest to the study of

It

upon the students' deductive powers and less upon his memory-thus tending to remove a reproach from the science as an educative subject. Moreover, the generalisations of the Law give the beginner a much sounder know. ledge of chemistry than he can get from the study of isolated and apparently unconnected reactions and properties

Salpeter und sein Ersatz. ("Saltpetre and its Substitutes"). By KONRAD W. JURISCH. Leipzig: S. Hirzel. 1908.

THE growth in importance and magnitude of the chemical industries connected with the artificial production of nitrogenous manures demands new books dealing with them, and this treatise on saltpetre is, no doubt, the forerunner of many similar works. The first part of it deals with the extraction, preparation, analysis, &c., of ordinary and Chili saltpetre; methods of analysis are given only in outline, and certain by-processes, such as the preparation of nitric acid, the chemistry and technology of ammonia, are not discussed, but full bibliographies, dating in one case from 1895 and in the other from 1830, of the literature of the subjects in all languages are given, together with some needs of plants as regards nitrogenous manures are disadditional notes on important articles and books. The cussed in some detail, and illustrations of the influence of different manures on the growth and development of plants are reproduced. The preparation and properties of calcium cyanamide are treated fully, and also the production of nitric acid from the air. The different factories which have sprung up in Norway are described and illustrated, and the rapid growth of this particular industry is made very evident.

("Studies in

Kolloidchemische Studien am Eiweiss.
Colloidal Chemistry with Albumen "). By W. Pauli.
Dresden Theodor Steinkopff. 1908.

THIS monograph is a reprint of a lecture which was delivered in Vienna in June, 1908, and published in the July number of the Zeitschrift für Chemie und Industrie der Kolloide. Its issue as a separate publication is justified by the admirable survey it gives of the author's valuable researches on albuminous substances and the

effects of salts upon them. These researches, which led to some results of the greatest importance, were ably conceived and skilfully performed, and were specially aimed at the reproduction of the conditions which obtain in the living organism, so that their application to the solution of physiological problems is at once apparent. One of the most important results obtained was the demonstration that the ions of neutral salts form adsorption compounds with albuminous substances, a theory which was put forward some time ago by the author and Prof. Loeb. Besides describing the experimental arrangements and the conclusions to be drawn from the results obtained, the author discusses briefly the bearing of his own and other investigators' work on physiological problems; he holds the view that the albuminous constituents of the plasma are the substances which are first attacked by the ionised compounds.