If next we suppose the rod or cord to be slightly twisted about its axis, so that its directions of maximum and minimum elasticity shall lie on two rectangular helicoidal surfaces (heliçoïdes gauches), and if, while regular rectilineal vibrations are maintained at one point of it with a period to which the wave length corresponding is a very large multiple of the step of the screw, the substance be made to rotate so rapidly as to make the velocity of a point carried along one of the screw surfaces in a line parallel to the axis be equal to the velocity of propagation of a wave, it is clear that a series of sensibly plane waves will run along the rod or cord with no rotation of the plane of vibration. The period of vibration of a particle will be, approximately, the same as before, that is, approximately, equal to

2π'

na Its velocity of propagation will therefore be and, if s be the step of the screws, the period of rotation of the substance, to fulfil

n

na

or its angular velocity

Now

na

8

the stated condition, must be it is easily seen that the effects of the rapid rotation, and the effects of the slight twist, may be considered as independently superimposed; and therefore the effect of the twist, with no rotation of the substance, must be to give a rotation to the plane of vibration equal and contrary to that which the rotation of the substance would give if there were no twist. But the effect on the plane of vibration, due to an angular velocity w, of rotation of the substance, is, as we have

8nw3
λ4

seen, one turn in wave lengths; and therefore it is one turn in

na

wave lengths when the angular velocity is Hence the effect of a twist amounting to one turn in a length, s, a small fraction of the wave length, is to cause the plane of vibration of a wave to turn round with the forward propagation of the wave, at the rate of n1 a3 one turn in 8 wave lengths, in the same direction as that of a

point kept on one of the screw surfaces.

From these illustrations it is easy to see in an infinite variety of ways how to make structures, homogeneous when considered on a large enough scale, which (1) with certain rotatory motions of component parts having, in portions large enough to be sensibly homogeneous, resultant axes of momenta arranged like lines of magnetic

VOL. VIII,

P

force, shall have the dynamical property by which the optical phenomena of transparent bodies in the magnetic field are explained; (2) with spiral arrangements of component parts, having axes all ranged parallel to a fixed line, shall have the axial rotatory property corresponding to that of quartz crystal; and (3) with spiral arrangements of component groups, having axes totally unarranged, shall have the isotropic rotatory property possessed by solutions of sugar and tartaric acid, by oil of turpentine, and many other liquids.

V. "Rescarches on the Action of Sulphuric Acid upon the Amides and Nitriles, with Remarks on the Conjugate Sulpho-acids." By GEORGE B. BUCKTON, Esq., F.L.S., F.C.S., and A. W. HOFMANN, Ph.D., F.R.S. Received May 13, 1856.

(Abstract.)

Since we had the honour of addressing the Royal Society upon the subject of the behaviour of acetamide and acetonitrile towards sulphuric acid, we have completed our experiments upon the amides and nitriles, and extended our researches to other groups of bodies. The results of these additional inquiries we now beg to present in the form of a second short summary, the analytical details and the more extended description of the new compounds being given in the complete memoir, which, at the same time, we have the honour of submitting to the Society.

Before proceeding, however, to give an account of our new compounds, it may be desirable to state that several considerations, suggested by the progress of our inquiry, have induced us finally to adopt the name of Disulphometholic acid instead of the provisional term Tetrasulphomethylic acid under which we have described, in our first communication, the new acid generated by the action of sulphuric acid upon acetamide and acetonitrile.

ETHYL-SERIES.

Action of Sulphuric Acid upon Propioniirile.

Considerable difficulty is experienced in preparing this nitrile in a

state of purity. It was finally obtained by acting upon propionamide with anhydrous phosphoric acid.

When three parts by measure of the nitrile are cautiously mixed with two parts of fuming sulphuric acid, and heat is applied, the liquids enter into a sort of ebullition, carbonic acid being copiously evolved; at the same time a portion of propionic acid passes into the receiver, the amount of which may be lessened by raising the temperature only gradually.

At the close of the operation a tenacious mass is found in the retort, which, when dissolved in water and neutralized with carbonate of barium, furnishes two rather soluble but readily crystallizable salts, very difficult to separate one from the other. Their isolation may be conveniently effected, by converting them into the corresponding ammoniacal compounds, by precipitating their solution with carbonate of ammonium.

The filtrate yields two substances, one of which crystallizes, while the other is quite uncrystallizable.

The latter substance, when long digested with carbonate of barium, produces crystals of a barium-salt whose analysis gives numbers leading to the formula

C6 (H, Bа) S2 010

4

This substance is obviously sulphopropionate of barium, the compound next in series to the sulphacetate discovered by M. Melsens. It is generally deposited from its solution in fine silky crystals, which arrange themselves in spherical groups. They are very stable, and bear a high temperature without decomposition.

The salt associated with the uncrystallizable sulphopropionate of ammonium crystallizes with ease, either in rectangular prisms or in octohedra. Similarly converted into a barium-compound, it was found by analysis to contain at 100° C.,

C4 (H4 Ba2) S4 O12+2HO.

It forms regular six-sided plates, which are moderately soluble in water, but insoluble in alcohol and in ether. It loses two equivalents of water of crystallization between 100° and 170°, but a few degrees above this temperature it is decomposed with blackening, yielding water, sulphurous acid, volatile organic products, and sulphate of barium.

We designate this salt as disulphetholate of barium.

Disulphetholic acid is prepared by precipitating a solution of the barium-salt with sulphuric acid, the excess of which is again removed by digestion with oxide of lead, and subsequent treatment with sulphuretted hydrogen. It is a crystalline and stable compound, very acid to the taste, and very deliquescent. With oxide of lead, or with carbonate of silver, it readily forms the respective salts, both of which are crystalline.

After what has been said with reference to the action of sulphuric acid upon acetamide, it is scarcely necessary to remark that the sulphopropionates and disulphetholates may be prepared with equal, or even greater facility from propionamide. Care, however, should be taken to use the amide in a perfectly dry state, which prevents in great measure the formation of free propionic acid.

PROPYL-SERIES.

Action of Sulphuric Acid upon Butyramide.

Equal parts by volume of melted butyramide and Nordhausen sulphuric acid evolve much heat when mixed together. In the reaction two acids are eliminated, showing that the series bears a strict analogy with the deportment exhibited by the preceding group.

As the ammonia-salts of these acids are wholly uncrystallizable, their separation is almost impossible. The barium-compounds also are scarcely to be obtained of a definite form, so that it is a matter of great difficulty to procure salts of sufficient purity for exact estimation. Recourse was had to fractional precipitation by alcohol.

The first salt which was deposited formed minute grains, which adhered strongly to the sides of the glass vessel containing the solution. It gave a percentage of barium which unmistakeably indicated the formula Cg (He Bag) S O109

which is that of sulphobutyrate of barium.

This substance in its reactions closely resembles (with the exception of its greater solubility in water) the corresponding body of the ethyl-series. It burns like tinder, with evolution of sulphurous acid, and leaves a residue of sulphite and sulphate of barium. The aqueous solution presents a gummy mass on evaporation.

A further addition of alcohol to the mother-liquor of the sulphobutyrate of barium throws down a flocculent precipitate, which is

very soluble in water. It was purified by repeated and partial precipitation with alcohol. This substance, when dried at a temperature of 165° C., furnished upon analysis numbers agreeing with the expression C (He Ba2) S4 012

6

which is that of disulphopropiolate of barium.

PHENYL-SERIES.

Action of Sulphuric Acid upon Benzonitrile.

From the results obtained in the study of the methyl-, ethyl-, and propyl-series, we may fairly infer that all the homologues of other groups will exhibit a similar deportment.

It appeared, however, desirable to extend our researches to a class of bodies which are analogous (not homologous) to the preceding series.

Sulphuric acid appears to act with much less energy upon benzonitrile or cyanide of phenyl than upon the foregoing nitriles. No evolution of gas is observed until the mixture of the two substances is strongly heated, and then so much sulphurous acid is formed from charring of the cyanide that its presence is almost entirely masked.

The digestion was continued for two hours, after which the dark residue was treated in the usual manner for the soluble barium-salts. That first obtained consisted of sulphobenzoate of barium. For identification, both the neutral and acid compounds were prepared, the respective formula of which,

An examination of the mother-liquor proved, as we had anticipated, the presence of a more soluble salt. By rapid evaporation it appears as an amorphous mass, but a drop allowed to dry spontaneously on the stage plate of the microscope exhibits it in the form of minute shuttle-shaped crystals.

The formula of this body, deduced from a sulphur- and bariumdetermination, is

C12 (H, Ba) S, O129

which characterizes it as disulphobenzolate of barium.