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Free Base. The separation of the base from the hydrochlorate presents no difficulty. This salt dissolves in alcoholic ammonia, giving rise to a wine-yellow solution. This liquid contains the base in the free state, together with chloride of ammonium. On ebullition the blue colour reappears, the salt being reproduced with evolution of ammonia. Addition of water, on the other hand, produces a white or greyish precipitate, consisting of triphenylic rosaniline. The best mode of procuring this compound in a state fit for analysis is to pour the concentrated solution of the hydrochlorate in ammoniacal alcohol into water, when the base separates as a curdy mass which soon collects upon the surface of the liquid. During the process of washing, and especially of drying, even in vacuo, the greyish powder gradually assumes a blue tint. The vacuum-dry substance, when exposed to 100°, assumes a deep brown colour, which it retains on cooling; at 100° it slightly fuses, but does not change weight.

Triphenylic rosaniline shows a tendency to crystallize, but hitherto I have not been able to obtain it in distinct crystals. The solution in alcohol and also in ether (which dissolves the base with the greatest facility) have, even on spontaneous evaporation, deposited the base in the form of an almost amorphous residue.

Analysis assigns to this base the composition which corresponds to that of the hydrochlorate previously examined, namely

C33 H33 N, O=C20 H1e (C, H,), N1, H, O.

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Triphenylic rosaniline is thus seen to separate from its saline combinations in the state of hydrate, exactly like rosaniline itself.

I have endeavoured to obtain further confirmation of these results by the analysis of several salts of triphenylic rosaniline. These salts were invariably prepared by treatment of the free base with the free acids. They resemble in their properties the hydrochlorate-so much so, indeed, that they could not possibly be distinguished without analysis. The nitrate is perhaps a little more, the sulphate a little less soluble in alcohol than the hydrochlorate. The following salts were submitted to analysis :

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Rosaniline, it will be remembered, forms, in addition to its ordinary monatomic compounds, a series of triatomic salts, which are more soluble and comparatively colourless. I have vainly endeavoured to prepare similar compounds with the triphenylic derivative of rosaniline.

Action of reducing agents upon Triphenylic Rosaniline.-Remembering the facility with which rosaniline is attacked by reducing agents, and the valuable help which the examination of the leucaniline thus produced afforded in establishing the formula of rosaniline, I was led to study the deportment of the triphenylic derivative under similar circumstances. This substance indeed is readily reduced both by nascent hydrogen and by sulphide of ammonium.

The alcoholic solution of the chloride, when left in contact with zinc and hydrochloric acid, is rapidly decolorized. The clear liquid when mixed with water yields a white, scarcely crystalline precipitate, which may be freed from chloride of zinc by washing, and separated from accidental impurities by solution in ether, in which it is easily soluble.

If the reduction be effected by sulphide of ammonium, the product is apt to be contaminated with sulphur and secondary products. In this case the separation has to be accomplished by treating the crude mass obtained. in the reaction with bisulphide of carbon, which dissolves both the sulphur and the product of the reduction, leaving behind a brown resinous substance, the nature of which is not yet investigated. The mixture remaining after the evaporation of the bisulphide of carbon is repeatedly boiled with soda, which dissolves the sulphur; the residuary compound is then finally purified by solution in ether, from which it is deposited on spontaneous evaporation in the form of a friable resin.

Unfortunately this compound is no longer basic, so that it was impossible to combine it with acids; but its combustion has furnished numbers agreeing exactly with the composition assigned to it by theory, namely C39 H33 N2=C2, H13 (C, H2), N2.

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The compound accordingly is triphenylic leucaniline. It will be observed that the triphenylic derivative, like leucaniline itself, is anhydrous—a constancy of behaviour in the normal and derived compounds which has already been pointed out in the case of rosaniline and its phenylic derivative. Under the influence of oxidizing agents, the hydrogenetted body is rapidly reconverted into the compound from which it has been obtained. The experiment succeeds best with platinum-chloride. The colourless solution of triphenylic leucaniline, when boiled with a few drops of dichloride of platinum, immediately assumes the splendid blue colour which distinguishes the salts of the non-hydrogenetted base.

The transformation of aniline-red into aniline-blue possesses a variety of interests. A lively imagination might feel tempted to speculate on the relation between colour and composition; but there are other questions claiming more immediately the attention of the experimentalist.

Up to the present moment chemists were unacquainted with a method of phenylation. The chloride, bromide, and iodide of the phenyl-series have been but imperfectly studied; but we are sufficiently acquainted with them to know that they are far from possessing the plastic character of the corresponding compounds of the methyl- and ethyl-series, which

confers such value upon these substances as agents of research. We are unable to substitute phenyl for hydrogen by processes borrowed from the experience gathered in experimenting with the ordinary alcohols. Diphenylamine and triphenylamine are substances existing at present only in the conception of the chemist. It was reserved for the peculiar, I might almost say instinctive mode of experimenting belonging to industry to fill up this blank.

The transformation of rosaniline into aniline-blue suggests some other questions which must not altogether remain unnoticed here, although I hope to enter more fully into this subject elsewhere. Does this transformation simply involve an interchange between the hydrogen and phenyl atoms, or does the rosaniline molecule lose ammonia, which is replaced by aniline?

I do not pretend to answer this question; but I beg leave to record some experiments as materials towards the solution of the problem.

Methylic, Ethylic, and Amylic Derivatives of Rosaniline. The interpretation of the results delineated in the previous pages legitimately suggested the study of the behaviour of rosaniline under ordinary processes of substitution-in other words, the treatment of this base with the iodides of methyl, ethyl, and amyl. I will not describe the pleasure with which I observed the intense blue colour of the mixture of rosaniline with these iodides when, after a day's digestion, I took the sealed glass tubes from the boiler. The action of iodide of methyl and ethyl is readily accomplished at 100° C.; iodide of amyl requires a temperature of from 150° to 160°. The presence of alcohol facilitates the reaction.

Up to the present moment I have only examined in detail the action of iodide of ethyl. The product of this action is an iodide which dissolves with a magnificent blue colour in alcohol. The tinctorial powers of this solution are scarcely inferior to that of rosaniline itself; and industry will probably not disdain to utilize this latest indication of science.

The blue ethylated derivative of rosaniline, as might have been expected, presents in its properties greater analogies with rosaniline itself than the triphenylic compound. This analogy suggested difficulties in the separation of the two substances which it appeared better to avoid. The iodide produced by the reaction was therefore at once decomposed by soda, and the ethylic derivative, together with the unaltered rosaniline, again submitted to the action of iodide of ethyl. After this process had been once more repeated, the alcoholic solution of the final product was precipitated by water, which separated a soft resin-like substance, solidifying on cooling with crystalline structure, and exhibiting a very peculiar metallic lustre intermediate between those presented by the salts of rosaniline and of its phenylic derivative. Crystallization from dilute spirit furnished the iodide in the pure state. The results obtained in the combustion and iodine determination of this substance agree with the formula C23 H3 N2 I=C20 H1 (C2 H.), N ̧ C, H, I,

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showing that the frequent repetition of the process of ethylation had produced, not the hydriodate of triethylic rosaniline, but the ethyliodate of this substance, a result which appeared particularly welcome, inasmuch as it threw at the same time considerable light upon the degree of substitution which belongs to rosaniline itself.

The facts elicited by the study of the action of iodide of ethyl upon rosaniline open a new field of research, which promises a harvest of results. The question very naturally suggests itself, Whether the substitution for hydrogen in rosaniline of radicals other than methyl, ethyl, and amyl, may not possibly give rise to colours differing from blue; and whether chemistry may not ultimately teach us systematically to build up colouring molecules, the particular tint of which we may predict with the same certainty with which we at present anticipate the boiling-point and other physical properties of the compounds of our theoretical conceptions?

This idea appears to have floated in the mind of M. E. Kopp when, with remarkable sagacity, he concluded his paper on Aniline-red* in the following terms:-"The hydrogen of this substance being replaceable also by methyl, ethyl, and amyl, &c., we may anticipate the existence of a numerous series of compounds, all belonging to the same type, and which might constitute colouring matters either red, or violet, or blue.”

Conceptions which only two years ago appeared little more than a scientific dream, are now in the very act of accomplishment.

I propose to continue these researches, and intend in a later communication to submit to the Royal Society the results obtained in the study of two other colouring matters derived from rosaniline, viz. anilinegreen and aniline-violet.

November 26, 1863.

Major-General SABINE, President, in the Chair.

In accordance with the Statutes, notice was given from the Chair of the ensuing Anniversary Meeting, and the list of Officers and Council proposed for election was read as follows:

President.-Major-General Edward Sabine, R.A., D.C.L., LL.D.
Treasurer.-William Allen Miller, M.D., LL.D.

Secretaries.

____ William Sharpey, M.D., LL.D.

George Gabriel Stokes, Esq., M.A., D.C.L.

Foreign Secretary.-Prof. William Hallows Miller, M.A.

Other Members of the Council.-James Alderson, M.D.; George Busk, Esq., Sec. L.S.; Col. Sir George Everest, C.B.; Hugh Falconer, M.A., M.D.;

* Ann. de Chim. et de Phys. [3] lxii. 230.

John Hall Gladstone, Esq., Ph.D.; Joseph Dalton Hooker, M.D.; Henry Bence Jones, M.A., M.D.; Prof. James Clerk Maxwell, M.A.; Prof. William Pole, C.E.; Archibald Smith, Esq., M.A.; Prof. Henry J. Stephen Smith, M.A.; The Earl Stanhope, P.S.A., D.C.L.; Prof. James Joseph Sylvester, M.A.; Thomas Watson, M.D., D.C.L.; Prof. Charles Wheatstone, D.C.L.; Rev. Prof. Robert Willis, M.A.

The question of Captain Ibbetson's readmission into the Society was put to the ballot, and, the ballot having been taken, Captain Ibbetson was declared to be readmitted.

The following communications were read :—

I. "Account of Magnetic Observations made between the years 1858 and 1861 inclusive, in British Columbia, Washington Territory, and Vancouver Island." By Captain R. W. HAIG, R.A. Communicated by the President. Received November 4, 1863.

(Abstract.)

This paper contains the results of magnetic observations made between the years 1858 and 1861 inclusive, in British Columbia, Washington Territory, and Vancouver Island. The results are tabulated; and from them the direction and position of the lines of equal dip, total force, and declination or variation are determined.

Three maps at the end show the position of these lines, the stations of observation, and the observed values of the three magnetic elements at each station.

II. "On Plane Water-Lines." By W. J. MACQUORN RANKINE, C.E., LL.D., F.R.SS.L. & E., Assoc. Inst. N.A., &c. Received July 28, 1863.

(Abstract.)

1. By the term "Plane Water-Line" is meant one of those curves which a particle of a liquid describes in flowing past a solid body when such flow takes place in plane layers. Such curves are suitable for the water-lines of a ship; for during the motion of a well-formed ship, the vertical displacements of the particles of water are small, compared with the dimensions of the ship; so that the assumption that the flow takes place in plane layers, though not absolutely true, is sufficiently near the truth for practical purposes*.

2. The author refers to the researches of Professor Stokes (Camb. Trans. 1842), "On the Steady Motion of an Incompressible Fluid," and of Pro

* As water-line curves have at present no single word to designate them in mathematical language, it is proposed to call them Neoids, from vnòs, the Ionic genitive of vavs.

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