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(69 obs., two thermometers); the direct process gave 610-85 (28 obs., one thermometer). Dibromaniline was prepared as stated above (B): the direct acetic process yielded me little, if any, with the same ratio of reagents. The fusion-point was 780.82 (100 obs., two thermometers). Tribromaniline from acetanilide melted at 116.22 (30 obs., one thermometer); that which was made by the direct acetic process melted at 1169.28 (42 obs., two thermometers).

From purified aniline only a very minute amount of moniodapiline was obtained by three trials of a direct action in the ratio

PbO 2C6 HÈN: 1?. In presence of plumbic oxide (C6 HPN:12:

2 the yield was rather greater ; but the fusion-point of the portion volatile in steam gradually rose on repeated crystallization to 86° and beyond, with no certain indication of a settlement. This product appeared to contain traces of ordinary moniodaniline; but after the final crystallization it yielded no platinic salt insoluble in alcohol and ether. The residue in the retort, nonvolatile in steam in presence of potash, contained aminic bodies soluble in dilute aqueous hydric chloride. These are perhaps the missing poly-iodanilines. 12 Pemberton Terrace,

St. John's Park, N.

III. Carbon and Hydrocarbon in the Modern Spectroscope. By Piazzı Smyth, Astronomer Royal for Scotland*.

[With Two Plates.] IN N the November Number of the Philosophical Magazine

appears a paper “On the Spectrum of Carbon," by an author whose name is well known and widely respected both in spectroscopic inquiries in general, and carbonaceous spectra in particular, viz. W. Marshall Watts, D.Sc. Yet there would seem to be a something somewhere wanting in the said paper if it is to represent the state of knowledge in 1874 rather than 1854, and to lead towards the discovery of truth as it is in nature.

The author sets out by suggesting what he considers an improved method for astronomers in observing the rather puzzling spectra of comets, viz. "to work by eye-estimations of the distance of the bands from the known bands of some equally faint spectrum, made to occupy the lower portion of the field of view, provided,” says he, “a faint spectrum can be found possessing a sufficient number of well-defined bands in the region of the spectrum

* Communicated by the Author.

hometers); the direct process gave 61085

meter). Dibromaniline was prepared as e direct acetic process yielded me little, if

ratio of reagents. The fusion-point was two thermometers). Tribromaniline from

116°22 (30 obs., one thermometer); that the direct acetic process melted at 1160:28 ometers). line only a very minute amount of moniodaby three trials of a direct action in the ratio

PbO resence of plumbic oxide (C® H’N:12:

greater ; but the fusion-point of the portion radually rose on repeated crystallization to

ith no certain indication of a settlement. red to contain traces of ordinary moniodaniinal crystallization it yielded no platinic salt

and ether. The residue in the retort, non

presence of potash, contained aminic bodies queous hydric chloride. These are perhaps danilines.

to be mapped." This, as italicized by him, is very clear; and he finds such a reference in what he calls the carbon-spectrum, but which others before him, whom he does not mention, have called the spectrum of carbohydrogen, of acetylene, of marshgas, and of general blue base of fame.

Impressed next with the importance of the places of the bands of that spectrum being known to great accuracy, Dr. Watts proceeds to give his own recent, and doubtless very good, measures of the wave-lengths of certain fine lines therein, and concludes with stating what substance the whole collection is the spectrum of, and what it is not, both in chemistry and physics.

The principle involved. Now to the principle of spectroscopic observation announced in the first part of the paper I certainly cannot object, seeing that it is, step by step, the ve

very

method and the very referencespectrum which I have been employing for four years past, and am still using in this royal observatory, and have often published upon, hoping to promote its general adoption. My first attempt indeed was not very successful ; for having sent a paper . on the subject to the Royal Astronomical Society on May 30, 1871, with the request that it might be read at the next meeting and printed in the following Montbly Notices,' that learned body (which is a very excellent body except in so far as it deals in the accursed thing for all free countries, of secret committees) chose to keep my paper back for six months without rendering any reason why

However, I having met, during those months, with Professor Swan of St. Andrews, who first accurately measured that spectrum’s lines, so far back too as in 1856—and I having held forth to him on the delightful and universal reference for faint astronomical spectra which I had found in that chemical spectrum which he had previously made so peculiarly his own, both by a priority without any question, and an accuracy which Professor Kirchhoff has since then pronounced to be classical,—he was induced to go to Section A of the British Association, then meeting in Edinburgh, and gave them a good and sound paper on the subject, besides furnishing me with his own special reductions of some of his angles of the , refractive indices of the lines into wave-lengths, agreeably with Angström's normal solar spectrum.

Afterwards, too, I not only printed the so-long-stopped paper in the thirteenth volume of the Astronomical Observations of the Royal Observatory, Edinburgh (together with Professor Swan's wave-lengths as above), but in the beginning of 1872 practised the method still further on the zodiacal light at Palermo, and on

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| Hydrocarbon in the Modern Spectroscope.
MYTH, Astronomer Royal for Scotland*.

[With Two Plates.]
er Number of the Philosophical Magazine
er On the Spectrum of Carbon,” by an

is well known and widely respected both in ries in general, and carbonaceous spectra in

Marshall Watts, D.Sc. Yet there would thing somewhere wanting in the said paper the state of knowledge in 1874 rather than towards the discovery of truth as it is in

out by suggesting what he considers an imastronomers in observing the rather puzzling viz. "to work by eye-estimations of the disfrom the known bands of some equally faint occupy the lower portion of the field of view, "a faint spectrum can be found possessing a well-defined bands in the region of the spectrum omniunicated by the Author.

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truth to assert that the number of known bodies may soon be doubled.

§ 38. Geological.—The behaviour of mixtures of salts will again offer a new chapter for study; and I suppose we may expect that much light will be thus thrown upon some of the most obscure geological questions. For though we have been considering above cryohydrates (that is, compounds of water solidifying below the freezing-point of water), there can be no discontinuity separating the medium water with its peculiar temperature of solidification from other media of very different melting-points. We know already, indeed, very many instances in which the mixture of two bodies has a lower melting-point than either of its constituents. What must happen, then, if a mass of molten rock, such as a silicate, is saturated at a high temperature with another silicate ? When the mixture cools, the second may separate out in the solid form, perhaps as quartz, perhaps as felspar, or what not. Anon, at a certain lower temperature, solidification takes place between the medium and the dissolved rock in definite proportion-definite, though perhaps not necessarily in chemical ratio, but presenting that mineralogical ratio which is so striking, and which has not hitherto been satisfactorily explained.

§ 39. Constant temperatures.-Perhaps one of the most interesting aspects of the experimental results is the establishment of fixed temperatures below zero. With the exception of the melting-points of a few organic bodies such as benzol, and the boiling-points of a few liquids such as liquid ammonia, sulphurous acid, and carbonic acid, and the rather ill-defined temperatures to be got by various freezing-mixtures, there are no means in the hands of physicists for obtaining and maintaining with certainty and ease a fixed temperature below 0° C. Now, if we surround a body with one of the solid cryohydrates described above, the body is kept at a corresponding temperature as long as any of the cryohydrate remains solid, and this with as much certainty as the temperature 0° C. can be maintained by melting ice. We thus command temperatures between -23° and 0° C. with the greatest precision.

§ 40. Invitation to others.— I need scarcely point out that the field of inquiry which has been here opened is far too large to be satisfactorily examined by one worker. It is notably at the commencement that the collaboration of many workers is most beneficial, so that fundamental errors may be quickly corrected. On this ground I respectfully invite my fellowlabourers to this branch of inquiry.

I have received through a considerable part of this inquiry much valuable assistance from my friend Mr. F. H. Marshall.

the number of known bodies may soon

- The behaviour of mixtures of salts will
apter for study; and I suppose we may
nt will be thus thrown upon some of the
ical questions. For though we have been
yohydrates (that is, compounds of water
e freezing-point of water), there can be no
ting the medium water with its peculiar
fication from other media of very different
e know already, indeed, very many instances
e of two bodies has a lower melting-point
nstituents. What must happen, then, if a
k, such as a silicate, is saturated at a high
nother silicate? When the mixture cools,
sparate out in the solid form, perhaps as

felspar, or what not. Anon, at a certain
solidification takes place between the medium
ock in definite proportion-definite, though
arily in chemical ratio, but presenting that

which is so striking, and which has not
actorily explained.
temperatures. Perhaps one of the most in-
of the experimental results is the establish-
ratures below zero. With the exception of
of a few organic bodies such as benzol

, and
f a few liquids such as liquid ammonia

, sularbonic acid, and the rather ill-defined temby various freezing-mixtures, there are no

II. On Aniline Derivatives.

By EDMUND J. Mills., D.Sc., F.R.S.* THE NHE following results in connexion with aniline derivatives

were obtained during the course of an investigation for which the substances that will be referred to were required.

Separation.—When chloraniline, bromaniline, &c. are prepared by acting on an anilide with chlorine &c., the function has usually a double period; so that mono-, di-, and tri- derivatives are generated in presence of each other. In order to separate these I proceed as follows. The mixed derivatives are immersed in a very large excess of aqueous hydric chloride (1 vol. common fuming chloride to 9 vols. water) and heated to nearly 100°, with frequent stirring, for about an hour in a loosely covered vessel; the whole is then allowed to cool down until the next day. The clear liquid contains only mono- and di- derivatives, the insoluble portion di- and tri- derivatives. The latter is submitted to repeated hydrochloric treatment as before, until the supernatant clear liquid no longer gives any precipitate with ammonia; it then consists of tri- derivative only-contaminated, indeed, with some black tarry products. This derivative can be purified by distillation per se, or from strong aqueous hydric chloride or potash-lime. The clear liquids are united and precipitated with ammonia during twenty-four hours, a large excess of ammonia being avoided. The precipitate is then washed, rapidly evaporated with hydric chloride to dryness on the water-bath, redissolved (or at any rate well stirred) in hot water, and left to cool thoroughly: the insoluble portion consists of di- derivative, and must be filtered off. The filtrate is again evaporated to dryness and stirred with hot water &c. Three evaporations to dryness are necessary, and usually sufficient; and the final solution contains mono- derivative only, which yields but an inappreciably small amount of insoluble residue when so evaporated. The mono- derivative can be purified by distillation from aqueous soda in a current of steam ; the di- derivative by distillation per se, or by successive crystallizations from naphtha and spirit.

When aniline is intended to be converted into chlorine, bromine, or iodine derivatives, it should be dried and purified by cohobation for a few hours with about one eighth to one sixteenth of its weight of mercuric chloride, bromide, or iodide respectively. Subsequent fractional distillation easily furnishes a very pure product. Only aniline so purified is referred to in the following experiments.

Preparation.-- (a) Aniline is cohobated with glacial hydric

of physicists for obtaining and maintaining
ease a fixed temperature below 0°C. Now,
ody with one of the solid cryohydrates de
body is kept at a corresponding tempera-
of the cryohydrate remains solid, and this
nty as the temperature 0° C. can be main-
2. We thus command temperatures between

the greatest precision.
others.--I need scarcely point out that the
ch has been here opened is far too large
xamined by one worker. It is notably at
at the collaboration of many workers is
hat fundamental errors may be quickly
ground I respectfully invite my fellow-
h of inquiry:
ugh a considerable part of this inquiry
e from my friend Mr. F. H. Marshall.

* Communicated by the Author.

acetate for some hours so as to form acetanilide, which is then purified by crystallization. The acetanilide is powdered, suspended in water, and treated with excess of bromine or chlorine (Proc. Roy. Soc. vol. x. p. 589) : the product is heated with powdered potash, moistened with spirit. This method gives good results. The product consists chiefly of mono- and tri- derivatives.

(B) It is not necessary to prepare acetanilide; a solution of dry aniline in glacial acetate answers equally well. Aniline is dissolved in 2-3 vols. of acetate, and chlorine- or brominevapour passed over the surface of the mixture, which must be well agitated. [In the case of bromine-vapour, the operation is performed in a warm closet, and the bromine is volatilized slowly from a retort, which must be heated by a small flame placed a considerable distance below. It is very easy thus to manage so that, while vapour comes over freely, no drops of bromine are delivered from the tube of the retort. This tube should be bent vertically downwards, and nearly touch the surface of the aniline mixture in the flask where the operation is conducted.] Considerable heat is evolved at first. As the reaction proceeds, the mixture becomes thicker, and partially solidifies; and at this point the operator will arrest it if he requires a minimum of tri- derivative, but continue until total solidification ensues if he wishes the triderivative to be a maximum. The whole may, if desired, be again submitted to further action by gently heating with more glacial acetate, wbich causes solution to occur. The cooled mass is heated to 100° under water, and afterwards cooled therewith. The supernatant liquid is filtered off and precipitated with alkali: this precipitate contains mono- and di- derivatives. The insoluble portion is mixed with powdered potash, moistened with spirit, and then heated in order to destroy any traces of anilide that may have been formed. The three derivatives are separated from the dark mass as already stated. The distinguishing feature of this mode of reaction is, that it is completely under the control of the experimenter. The ratio C8 HP ON : Br2 furnishes chiefly dibromaniline. Doubtless this process applies to other amines.

(y) The direct action of chlorine &c. on aniline itself is not attended with satisfactory results; in presence also of water or aqueous hydric salt there is an enormous amount of by-product. Aniline purified by distillation with mercuric iodide yields exceedingly little moniodaniline.

(8) Aniline may be mixed with plumbic oxide, and iodine &c. added*. I have only succeeded in preparing traces of iodaniline in this way. A considerable amount of crude product is obtained,

* This is Stenhouse's method of iodating orcin,

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