is also nearly decolourised, changing to a pale brownish | yellow fluid, but the moment this is exposed to the air it assumes its original colour far more quickly than indigo. This remarkable fact may be strikingly illustrated by boiling an alcoholic solution of salt of mauveine with a few strips of zinc in a sealed tube from which the air has been previously removed. The dark purple solution will gradually lose its colour, and change to a very paleyellowish brown shade.

I have a tube containing some aniline purple decolourised in this manner, and now if I open it, the air rushes in and the solution instantly assumes the ordinary purple colour. Ordinary indigo is quite insoluble in water, and, therefore, its property of becoming soluble, as well as colourless, when treated with reducing agents, is of great practical value, as the dyer, by immersing his goods in this solution of indigo, and then exposing them to the oxidising influence of the air, gets the colouring matter firmly fixed in the fibre of his materials. But as the mauve is always soluble in water, this property has not been found of any practical value.

Aniline purple, when introduced as a dye, being the first colour of its kind, had to encounter many prejudices, and, on account of its peculiar nature, required the adoption of new or modified processes for its application. These difficulties, however, once overcome, its progress was very rapid. At first it was principally employed by the silk dyer and printer, its application to silk being comparatively easy, but it was not used by the calicoprinter till a few years afterwards.

I distinctly remember, the first time I induced a calicoprinter to make trials of this colour, that the only report I obtained was that it was too dear, and it was not until nearly two years afterwards, when French printers put aniline purple into their patterns, that it began to interest British printers.

It will be seen that to introduce a new coal-tar colour after the mauve was a comparatively simple matter. The difficulty in the manufacture of all the raw materials had been overcome, as well as the obstacles in the way of the practical applications of an aniline colour to the arts.

We will now turn our attention to a colouring matter which has often been confounded with aniline purple. 1 have designated it as "Runge's blue," as it was first observed by Runge. I have mentioned that Runge, when he first obtained aniline, termed it "kyanol," or blue oil, on account of the blue-coloured solution it gave with chloride of lime.

After discovering the mauve, I naturally made experiments with this coloured product of Runge's, to see if it contained aniline purple, but my experiments answered the inquiry in the negative. A few years afterwards, however, I was puzzled by finding that French manufacturers were beginning to produce aniline purple by the agency of chloride of lime and a salt of aniline; being much occupied at that time, I was unable to look carefully into the matter; and it was not until investigating these apparently opposite results a short time since that I was able to understand them. I will perform Runge's experiments, and for that purpose will take a solution of hydrochlorate of aniline, and add to it a very dilute solution of chloride of lime (taking care not to add too much). The solution is now changing, and getting slightly opaque; by daylight it has an appearance like indigo, but if I render it clear by the addition of alcohol, and place it before the magnesium lamp, it is seen to be of a brilliant colour, and nearly pure blue, quite unlike aniline purple.

I have lately succeeded in obtaining this blue product in the solid condition by treating a solution of hydrochlorate of aniline with a dilute solution of chloride of lime, and precipitating the resulting colouring matter with common salt; it is thus obtained in an impure condition, and may be collected upon a filter; by treatment with cold ether or benzol, a large quantity of brown impurities are separated, the colouring matter being left in the solid

condition. This substance dissolves in alcohol, forming a nearly pure blue solution, and is capable of dyeing silk a blue or blue-violet colour.

An alcoholic solution of Runge's blue behaves with caustic potash quite differently to aniline purple, forming a brownish-red coloured solution instead of a violet. Therefore, there can no longer be any reason for confounding this body with aniline purple, it being entirely different, both in colour and chemical properties. But as this colouring matter is produced by oxidising hydrochlorate of aniline with chloride of lime, how is it that manufacturers have succeeded in preparing aniline purple with the same reagents? This question I find is very easy to answer: the manufacturer has gone a step further and boiled his product. Now, if I take a piece of silk dyed with Runge's blue, and, instead of boiling it, which would wet it, and make it difficult to manipulate, do that which is equivalent -steam it a very remarkable change takes placeRunge's blue being changed into the mauve. So, here we have cleared up the mystery, and find that by the action of chloride of lime on hydrochlorate of aniline, we first get Runge's blue. and then, by heating this blue we change it into mauve. Runge's blue is a very unstable body, and of no practical value, its alcoholic solution changing into mauve in a day or two. This change takes place directly by boiling.

We must now pass on to another colouring matter, in name well-known to all of you, I mean magenta, also called roseine, fuchsine, aniline red, and various other names. The discovery of this body and its manufacture were strangely dependent upon the source which had been selected for the preparation of aniline for the mauve. Had the aniline contained in coal-tar, or the aniline obtained from indigo, been employed for the preparation of the mauve, instead of that prepared from commercial benzol, magenta and its train of coloured derivatives would, in all probability, have remained unknown to this present day, from the simple fact that magenta cannot be produced from pure aniline, a second body being also required.

You will observe, by reference to the table of coal-tar products, that next to benzol there is a substance named toluol, a substance having a boiling point not very much above that of benzol, On this account toluol is always contained in commercial benzol, and possesses most of its properties. With nitric acid it forms nitrotoluol, very similar to nitrobenzol; with iron and acetic acid it is converted into a base, toluidine, very similar to aniline, except that it is solid instead of liquid, when pure. Therefore, aniline prepared from commercial benzol always contains a little toluidine, and this is the second body requisite for the formation of magenta.

An apparatus for the fractional distillation of coal-tar naphtha has been devised, so that its constituents may be almost. completely separated from each other, and thus pure benzol or pure toluol may be obtained. Having obtained these hydrocarbons, pure aniline and pure toluidine may be prepared and then mixed in the most suitable proportions for manufacturing magenta. This process is not very generally employed, however, but the quality of the mixture of aniline and toluidine is determined by distillation, noting the quantities which come over at different temperatures. The necessity of toluidine as well as aniline for the production of magenta was discovered by Dr. Hofmann, who found that it could not be produced by perfectly pure aniline, nor perfectly pure toluidine, but that a mixture of these two bases yielded it in quantity. Magenta was apparently first observed by Natanson, in 1856, when examining the action of chloride of ethylene on aniline, and afterwards by Dr. Hofmann, in 1858, when studying the action of tetrachloride of carbon on aniline, but industrially the discovery of magenta was made by M. Virguin, of Lyons, in 1859, three years after the mauve. M. Virguin's process con

* See "Clarke's Specification," June 5th, 1863, No. 1405.

42

sisted in treating commercial aniline with a fuming liquid, called tetrachloride of tin, and was first carried out by Messrs. Renard Brothers, of Lyons. Since 1859, patents have been taken out for the production of this colouring matter with aniline, and almost all chemicals known, whether capable or incapable of forming magenta. I may mention one process which was extensively employed, and is still used to some extent in Germany, and that is the method of making magenta with commercial aniline and nitrate of mercury. With care this process works very well, and the colouring matter produced is of good quality. When first introduced, magenta prepared by this method was not purified, but sent into the market in a crude form, so that before using it the dyer had to extract it with water. In the preparation of magenta by this process, all the mercury of the nitrate of mercury employed is recovered in the metallic state, but although this process may possess some advantages, yet the use of mercury salts is most undesirable on account of their fearfully deleterious influence upon the workmen.

The process, which has almost superseded all others, is that for the use of arsenic acid, as proposed by Medlock, and patented by him in January, 1860. This patent is notorious for the amount of litigation it has caused, showing that a patentee should not only be a discoverer but a lawyer, and even more, and able to discover precisely how much to claim and disclaim in his patent, and also to arrange his specification so that the intellects of the whole world may not be able to discover a single flaw in his description; and it is a common misfortune to inventors who wish to thoroughly protect themselves to find that they have claimed too much.

The manufacture of magenta, as now carried on, is a very simple process; it is conducted in an apparatus somewhat similar to that represented by fig. 5.

FIG. 5.

CHEMICAL NEWS, July 22, 1870.

means an

This operation requires some hours for completion, and this is determined by inserting an iron rod, from time to time, and drawing out a portion of the product for examination, as well as by the amount of aniline which distils over. When the heating has been completed, a steam-pipe is introduced into the apparatus, and steam blown through the fused mass; by this additional quantity of aniline is separated. The lid is then liberated and lifted, with the stirrer, from the apparatus, and the product left to cool before it is removed. A more elaborate and larger apparatus is sometimes used, which possesses considerable advantages over the smaller one. The iron pot is larger, and is provided with an outlet at the side, which is closed during the operation, and the shaft of the stirrer is hollow (as in the aniline apparatus described last lecture, fig. 4), and worked by steam. When the operation of heating is concluded, steam is blown down the shaft, and after the addition of water the product is boiled and run out of the outlet in the side of the pot; by this arrangement it is unnecessary to disconnect the lid of the apparatus, and the product does not require to be removed by mechanical means, as with the apparatus previously described.

The crude product obtained by heating aniline and arsenic acid, is next transferred to vats, boiled with water, and filtered. Common salt is then added, which precipitates the crude magenta; this is collected and dissolved in boiling water, again filtered, and the solution, on cooling, deposits the colouring matter in the crystalline condition. This, when re-crystallised, constitutes commercial magenta.

(To be continued.)

ON A CONTINUOUS WATER-BATH.*

AN apparatus of this kind, fully meeting all demands upon it, was some time since designed by Prof. Bunsen, who has abundantly stocked his laboratory with these, now, indispensables, which are only excelled for convenience and in saving of time and labour by the well-known filtering-pump. The want of just such a contrivance as this will have been felt by every chemist.

The method he adopts is to maintain a constant water level in a reservoir, which has free communication with one or with any number of the baths. In the accompanying a

In

This apparatus consists of a large iron pot, a, about 4ft. diameter, set in a furnace of brick-work; it is provided with a stirrer, b, worked by hand. All the gearing for this stirrer is fixed to the lid, so that stirrer, lid, and all may be lifted away by means of a crane or other suitable apparatus. There is also a bent tube fixed into the lid, and connected to a condensing worm, d, by means of a joint, which can be made or broken at pleasure. preparing magenta, a quantity of aniline, containing about 25 per cent of toluidine, and a nearly-saturated solution of arsenic acid, is introduced into this apparatus, and well mixed by working the stirrer; the proportions of the materials are in about the ratio of 1 of aniline to 15 of a 75 per cent solution of arsenic acid. When these are well mixed the fire is lighted. After the product has been heated for some time water begins to distil over, then aniline and water, and lastly nearly pure aniline.

B

cut, A is the bath in cross section, composed of an outer copper cylinder, through the centre of which runs a small tube of the same material, emerging at the upper end of the cylinder beneath a large flue. In the lower part of the cylinder an ordinary burner is permanently fixed, which heats the bath, and the products of its combustion is fitted to receive a large funnel, in which the capsules, are thus safely carried off. The upper part of the cylinder &c., of various sizes, containing the material to be evaporated are placed, the watery vapour escaping likewise

* Communicated by Dr. W. H. Wahl. From advance sheets of the Journal of the Franklin Institute.

lastly, the red colouring matter, called carthamic acid or carthamine.

We need not multiply such instances; a thorough and unprejudiced perusal of this book shows it has been written without sufficient care, and without the use of such books as the author speaks of in a somewhat contemptuous tone in his preface. The work certainly contains some good matter, but the whole ensemble has been evidently hurriedly compiled and is very ill digested. Such a work might be made to convey precise and correct information; but the present volume, we regret to say, does not do this. As to the purely chemical part, we abstain, purposely, from saying more than this--that the existence of really good books treating on qualitative, as well as quantitative, chemical analysis, renders superfluous what the author has published in these pages. The typographical execution of the book is good, and its index very complete.

Report on the Gas Nuisance in New York. By C. F. CHANDLER, Ph.D., Professor of Analytical and Applied Chemistry, School of Mines, Columbia College. Extract from the Fourth Annual Report of the Metropolitan (viz., Empire City, New York) Board of Health. New York: D. Appleton and Co. 1870.

We are indebted to Dr. Chandler for having forwarded a copy of this very interesting and elaborate report.

The nuisance, known as gas nuisance, which for a considerable period of time must have been intolerable to those districts of the City of New York situated near the localities from which it arose, is described by the author as having been caused by the exposure to air of the foul lime used in the so-called dry lime process of gas-purification by some of gas companies which supply the illuminating-gas to the city alluded to; and, in the report before us, the Metropolitan Company is the chief delinquent. This company, it appears, did not take the least heed of the complaints made; and, as a consequence, the Metropolitan (New York) Board of Health took vigorous steps to enforce the order made by it, whereby all the gas companies of the said city were compelled so to conduct their operations as to prevent injury to life and health. The Metropolitan Gas Company, instead of complying, commenced a litigation with the Board; and, as a consequence, there was commenced, before magistrates, an inquiry into the whole affair, and witnesses were heard on oath, and the whole question of gas-purification thoroughly gone into. Among the well-known scientific gentlemen summoned to appear and give evidence were-Dr. Chandler, as chemist to the Board of Health before referred to; Prof. B. Silliman, for the Gas Company; Prof. Wurtz, for the same. Prof. Silliman differed in opinion from Dr. Chandler as to the expediency of introducing the so-called iron purification-process, instead of lime; but he stated clearly and unequivocally that the process of purification as conducted by the Metropolitan Company was a nuisance which, by using simple precautions, could be avoided. After a great deal of delay, and the making of excuses of all kinds, the gas company referred to (having spent, in expert fees, counsel fees, &c., some 10,000 dollars) have complied with the order of the Board of Health, and introduced a system of purification which answers the purpose.

The Report before us (about 112 pages in small type, chiefly containing the full evidence given before the Court at New York) contains, as may be imagined, a very large amount of valuable scientific and practical matter relating to the purification of gas and gas manufacture in general; while the very compact and ably-written paper on the methods of gas-purification from Dr. Chandler's pen greatly contributes to make this work an excellent exposé of the subject treated of, as carried out in practice.

CHEMICAL NEWS,

CORRESPONDENCE.

THE SPECTROSCOPE

July 22, 1870.

APPLIED TO THE

BESSEMER PROCESS.

To the Editor of the Chemical News.

SIR, In the third volume of Crookes and Röhrig's Metallurgy" (which has just come into my hands), I find, on page 721, that, although the authors give me the credit of first proposing (in 1863) to use the spectroscope in the Bessemer process, they state that the actual practical application is due to Professor Lielegg, in 1868. As it seems to me, the merit of the practical application is rather due to the Styrian iron and steel makers, who adopted, as valuable, the results of Lielegg's experimentsresults which are, in fact, identical with those which I made known five years before. I then showed, beyond doubt, that the exact point of decarbonisation can be accurately arrived at by spectrum observations; and I frequently ascertained that this point exactly agreed with that at which the blast is turned off. The English steelmakers were shown in 1863 exactly that which the Styrian makers were taught in 1868. The English appear to think that the point can be detected by the naked eye with a sufficient degree of exactitude; the Styrians prefer to use the spectroscope.-I am, &c., HENRY E. ROSCOE.

Owen's College, Manchester, July 13th, 1870.

ABRIDGMENTS OF SPECIFICATIONS RELATING TO AERONAUTICS.

To the Editor of the Chemical News. SIR,-As compiler of the "Abridgments of Specifications relating to Aeronautics," I have to express my best thanks for the very favourable critique upon that little work that appeared in the CHEMICAL NEWS (vol. xxii., p. 19).

As the gentlemen that are deputed by the Commissioners of Patents to compile certain series of Abridgments are extraneous to the Patent Office, as they are chosen for their special knowledge of the subjects they undertake, and as their names are annually published in the Commissioners' Report, I was surprised that no recognition of my connection with that work appeared in your notice. I may perhaps be allowed to remark that the publication of the name of an abridger is possibly an act of justice to the public, as well as to himself. I therefore would suggest that you state my connection with that work, and with the introduction thereto, in any way that you may think best.-I am, &c.,

74, Brecknock Road, N.

July 13th, 1870.

W. H. WALENN.

[The compiler's name having only been given to us in writing, we did not feel at liberty to publish it when reviewing the work..-Ed. C. N.]

RUBIDIUM AND CESIUM.

To the Editor of the Chemical News. SIR,-I have found that, so far as my researches on rubidium and cæsium in sea-water and its products depend upon spectroscopic reactions, they are unreliable. In seaweed, as stated, I have found, by analytical methods, these alkalies; and, so far, the work can receive no further confirmation than it has already had. But, as respects the oxalate of calcium thrown down from sea-water, and the spectroscopic reactions of sea-shells and of limestone, I now believe the lines attributed to rubidium and cæsium

to be due to calcium and to strontium respectively. It is curious, and may, perhaps, partly excuse me, that the trace of strontium, at the most, that can be supposed to be contained in sea-water and in shells should, when so combined, give only the lime belonging to strontium marked delta in the maps, and therefore the fourth in order of intensity; but my further experiments leave me no room to doubt but it is so. This line, in my instrument, is not distinguishable from the blue line given by an impure compound of cæsium, no more than is the blue calcium line from the most characteristic of the rubidium lines. So far as I trusted to the spectroscope alone, so far I was deceived; but what was done independently of the spectroscope remains true.—I am, &c.,

Ramsey, Isle of Man, July 18th, 1870.

E. SONSTADT.

MR. BESWICK AND SWEDENBORG.

That a

To the Editor of the Chemical News. SIR, Mr. Beswick leads us to a mare's nest. certain quantity of dry salt disappears in water without increasing the bulk of the liquid is a very ancient observation. How could a fact at once so curious and obvious escape even a housewife's eye? The familiar anecdote will be remembered of King Charles II. testing the wits of a party of philosophers by requiring of them the reason why a fish immersed in a bucket full of water did not cause the water to overflow. Forthwith, several began to devise explanations, until one, shrewder than his fellows, suggested whether, indeed, a fish behaved like salt under

the circumstances!

Swedenborg's assertion that "the saline particle fits the convexity of the watery particles," and "is constantly attended by six aqueous globules," may be true, or may not. The chances are many against its truth; for such wanton fancies are rarely, if ever, verified by experience. At the time Swedenborg wrote (1721), mechanical or geometrical chemistry was in high vogue, and his conjectures would be regarded as perfectly legitimate. Lemery, a savant of great celebrity, contributed, in 1711, an elaborate paper to the Memoirs of the French Academy, wherein he argued that a fluid which dissolves a solid does so by pointed particles, which enter into pores of corresponding shapes and sizes in the solid. Thus nitric acid dissolves iron and copper, but not gold; because they have wide and numerous pores, and gold has not. How men had patience for such soothsaying is almost inconceivable at this day. Possibly we are quite as foolish in other ways, as posterity will in due course discover. Dalton extended the observation of the behaviour of chloride of sodium in water over the whole series of salts with which he was acquainted. His assertion that the initial fact of his investigation was new to him is surprising, and that in its scope, as completed by him, it was "the greatest discovery that he knew of, next to the atomic theory," scarcely less so. We must remember, however, that Dalton's general information was extensive. He was content to be ignorant of many things, that he might know a few thoroughly. He used to say he could carry all his books on his back. Moreover, in 1840, his well-worn brain was giving way, and he was writing under the exasperation of the rejection of his papers by the Royal Society.

not

No man holds Swedenborg's merits and memory in deeper reverence than I do, but for that reason fictitious claims advanced in his name affect me with shame and dismay. They only serve to perpetuate the prejudices against him, which I sorrowfully find to be almost insuperable.-I am, &c.

MISCELLANEOUS.

The Hall Testimonial.-On Thursday evening, the 14th inst., a large attendance of former pupils and friends of Mr. Thomas Hall, B.A., F.C.S., assembled at the City of London School, for the purpose of presenting that gentleman with a handsome testimonial, in recognition of his past services as Lecturer on Chemistry and Experimental Physics in that establishment. For the space of twenty-one years (since March, 1847) Mr. Hall had held this post, and successfully directed the studies of a large number of pupils, some of whom have, in consequence, acquired great distinction in the pursuit of science; and his retirement from the school was deemed a fitting occasion for presenting him with a testimonial, subscribed for last year, but only now handed to him, by reason of his compulsory absence from this country on account of ill health. The testimonial took the form of a handsome silver casket and purse of 200 guineas, and was presented by the late head master, the Rev. G. F. W. Mortimer, D.D., Canon of St. Paul's, who took occasion to testify to the successful results of Mr. Hall's teaching, and referred to a recent instance in which he had the

satisfaction of presiding, at Barnard Castle, when as many as forty-eight prizes and certificates were bestowed by the Department of Science and Art on the pupils of a gentleman who was himself instructed by Mr. Hall at the City of London School. After Mr. Hall had replied, the present head master (Rev. Edwin Abbot, M.A.), Mr. W. H. Perkin, Mr. J. Spiller, Mr. E. Ryder Cook (Treasurer), and the Hon. Secretary, Mr. J. T. Brown, spoke in complimentary terms on the occasion, and the meeting concluded with a vote of thanks to the Rev. Chairman.

An Improved Method of Producing White Pigments from Lead.-(Letters Patent to J. G. Dale and E. Milner, of Warrington.)-This invention relates to an improved method of manufacturing white-lead, "carbonate of lead," by the action of the soluble acid carbonates of the alkalies on litharge, hydrated oxides of lead, or insoluble basic salts of lead. The patentees propose to carry out their invention in two ways, and when soda is the substance chosen, they proceed (1) By mixing litharge, hydrated oxides of lead, or insoluble basic salts of lead, with an equivalent of bicarbonate of soda, together with sufficient water to form a stiffish paste. This mixture is ground in a suitable mill, small quantities of water being from time to time added as may be found requisite until the change of the lead bodies into carbonates is complete. The paste is now well washed with water, and the supernatant liquid which contains monocarbonate of soda is separated from the white-lead by filtration, and boiled down to dryness and disposed of as soda-ash; or it may be crystallised; or may be again converted into bicarbonate of soda, by treatment with carbonic acid, and used to convert further quantities of lead oxides, or insoluble basic salts of lead, into carbonates. Instead of grinding, the lead oxides, or insoluble basic salts of lead in a fine state of division, may simply be mixed with bicarbonate of soda and water and left to themselves, when the conversion into carbonates goes on in the same manner, only much more slowly. (2) They mix litharge, hydrated oxides of lead, or basic salts of lead, with caustic soda, monocarbonate of soda, or acid carbonates of soda, and sufficient water to form a stiffish paste. The mixture is now introduced into a suitable closed mill, and during the grinding a stream of carbonic acid gas is passed into it. After conversion of the lead bodies into carbonates, they are washed with water, and the supernatant liquid treated as before described. In carrying out their process by this secondly-described method, the patentees do not bind themselves to any particular proportion of lead oxides and soda, but equivalents of each answer very well. quantity of the soda salts may, however, be reduced with advantage if found desirable. Grinding may also be dispensed with, by mixing the lead oxides or insoluble basic

The