attracted toward the wall of a room; the reeds evidently seek to diverge beyond the limit of the dense electrical stratuin on the surface of the cylinder; and hence in charging the cylinder with one, two, three, &c. measured quantities of electricity, by which the thickness of the stratum may be supposed to be continually increased, we observe the distance of divergence become also increased. Beyond the extremity of the cylinder the balls would be attracted into the air with increased force in two directions, viz. from the extremity and from the side of the cylinder; hence they would appear as if repulsed sideways and outwards. These experimental facts, as it appears to me, are quite consistent with a uniform thickness of stratum or distribution of electricity upon the surface of a charged conductor. 20. The distance to which the attractive force of a charged surface extends will be directly as the quantity of electricity accumulated, as may be thus experimentally demonstrated. Exp. 12. Let the dise n, fig. 13, of the electrometer E be placed at a given distance above any point p of the rectangular plate R, suppose 5 of an inch. Charge the plate R with a given quantity of electricity, and observe the force at the given distance, 5 of an inch; let it be, for example, 16 degrees of the index at this distance. Let the distance be now increased; let it, for example, be made twice as great, or equal 1 inch; then the index will only show 4 degrees of force: the force will, in fact, be as the squares of the distances inversely. Under these cir cumstances, double the charge of the plate R; the force indicated will be again 16 degrees, that is to say, it will be as the square of the charge. Hence the distance to which an equal attractive force has extended from an area on the surface of the plate equal to that of the disc n, is as the quantity of electricity accumulated, that is, as the charge directly. Exp. 13. Place the electrometer E, fig. 14, at a given distance opposite any point of the cylinder e; charge the cylinder with a given measure of electricity, and note the degree of inclination of the arm of the instrument. Let the distance of the ball of the electrometer from the cylinder be now made twice as great, and the charge on the cylinder doubled; the inclination of the arm will remain the same. I endeavoured to find in this way the limits of distance at which the force was just sensible to very delicate electroscopes, and found them to be as the quantity of charge in the cylinder. Thus a given quantity being accumulated, the electroscope E (the sensibility of which could be very greatly increased by changing the position of a small piece of reed moveable on the lower arm, and by which it is poised) was placed at such a measured distance from the cylinder as admitted only of an extremely small movement, just as much as would indicate force. This distance being now made twice as great, the arm was observed to be similarly affected when the quantity of charge was doubled. These results accurately correspond with the law of striking distance in Lane's discharging electrometer, as I have before shown in my paper in the Royal Society's Transactions for 1834, p. 227. Since double, treble, &c. quantities of electricity exert attractive forces as the squares of these respective quantities, whilst, on the other hand, the forces decrease inversely as the squares of the distances between the striking points, we have necessarily the same striking force at all distances if we make the quantity of charge increase with the distance. Hence a charge which could strike over a distance of 5 of an inch would, on being doubled, strike over twice that distance, or 1 inch; that is to say, the force at that distance would be the same as seen in the experiments 11, 12, 13, &c. just described*. 21. In the case of a conducting surface terminating in an acute angle or point, we may still have an equal distribution of the charge, the only difference being a more free action of the charge upon the angular portion. Thus in fig. 16, let P be an insulated conductor charged with electricity, and suppose it to be transformed into a pointed conductor, Pp, by removing the triangular portions ac; then, as is evident, all the electrical stratum which formerly occupied those portions ac would become removed, and there would be less pressure or impediment, as it were, to the free inductive action of external matter on a given point p than there would be if the point were enveloped in electrical particles. The force, therefore, upon the principles already explained (15), would extend to a greater distance, and the striking distance of a point so circumstanced in respect of the electrical stratum greatly extended. The charge therefore would run off more freely, or be more freely received by a pointed conductor than by a point enveloped in surrounding electrical particles. 22. The result of experiment 9, and the deductions (15) and (16), enable us to operate upon metallic conductors in communication with the fixed disc of the electrical balance, or hydrostatic or other electrometers, without any care for the position * M. De la Rive, in his late comprehensive work on electricity, appears to consider this law of striking distance, as compared with the law of intensity, somewhat extraordinary. He says, "Ce qu'il y a d'assez remarquable, c'est que la distance à laquelle une décharge entre deux balles chargées d'électricités contraires peut avoir lieu, est simplement proportionelle aux quantités d'électricité, tandis que les forces attractives sont proportionelles aux carrés de ces forces." (Vol. i. p. 66.) It will be seen, however, that the above considerations fully explain the fact, and show it to be a necessary result of the laws of electrical force. of such conductors or the point of communication. Thus if P, fig. 16, be a rectangular plate connected with the fixed disc p of the balance by means of a slight wire, Pp, passing through a hole in the glass of the cage, the divergence of the needle n will be precisely the same when charged with the same quantity of electricity, in whatever position the plate P be placed, or with whatever point of it the wire Pp communicate. It will be, for example, just the same whether we place P transversely and centrally as at P, or in the direction of its length as P', the communicating wire being connected with either of its extremities. [To be continued.] X. Chemical Notices from Foreign Journals. [Continued from p. 59.] On the older view of the constitution of fulminic acid it was considered to be bibasic, and polymeric with cyanic acid. But this view did not sufficiently well account for some of its properties; and Gerhardt, in the first edition of his Organic Chemistry,' held, that from the explosive properties of the fulminates their nitrogen was contained, not as cyanogen, but partially as NO4, and he gave to fulminic acid the formula C4N (NO) H2. The constitution of this acid has lately been the subject of separate investigation at the hands of Schischkoff* and Kekulé*, who have arrived at results which are very similar, and include Gerhardt's supposition. From the highly explosive nature of the fulminates, and from the fact that cyanogen compounds are constantly formed in their various decompositions, Kekulé held that one half of their nitrogen was in the form of NO4, and the other half as cyanogen. It follows from this, that the other half must be present in another form, and would constitute with the remaining constituents a compound belonging to the methyle group. The formula of fulminating mercury would then be C2 (NO4) (C2 N) Hg2, and would exhibit in its composition the greatest analogy with a large class of compounds; for instance, C2 H, Cl, Cl, ČÍ, chloroform; C2 (NO4) Cl, Cl, Cl, chloropicrine; C2 H H H C2 N, acetonitrile (cyanide of methyle). Fulminating mercury would stand nearest to chloropicrine and acetonitrile. Like the former, it would be a nitro-compound, and like the latter, a cyanogen compound. It might be a nitroacetonitrile, whose two hydrogen atoms are replaced by mercury, and hypothetical fulminic acid would be a nitroacetonitrile, C2 HH (NO3) C2 N. * Liebig's Annalen, February 1857. In accordance with this interpretation, it was to be expected that fulminating mercury, when treated with chlorine, would yield chloride of cyanogen and chloropicrine; and experiment showed this to be the case. Kekulé obtained as products of this reaction gaseous chloride of cyanogen, and an oil which had all the properties of chloropicrine, but was probably contaminated with chloride of carbon. In this reaction no carbonic acid was formed, and the equation would thus be, C2 (NO4) (C2 N) Hg2+6C1 = C2(NO4)Cl3 + CyCl+2HgCl. of cyanogen. By distilling fulminating mercury with hypochlorite of lime, pure chloropicrine is obtained. By treating fulminating mercury with sulphuretted hydrogen, Kekulé obtained sulphocyanide of ammonium and carbonic acid, the occurrence of which in this reaction had hitherto been unnoticed. The reaction did not, however, give concordant results on analysis. The previous explanations given of this reaction are not quite correct: it is rather to be assumed that the free fulminic acid decomposes with sulphuretted hydrogen at the moment of its formation into sulphocyanide of ammonium and free carbonic acid, C2 (NO4) CyH2+2HS = 2CO2 + Cy NH4 S2. Fulminic acid. Sulphocyanide of ammonium. Schischkoff derives fulminic acid from the type biuret, to which he gives the rational formula 2(C2 O2 NH) NH3. If the hydrogen of the ammonia be replaced by the bibasic radical C4 H (NO), we get the formula of fulminic acid, 2(C2 O2NH). N(C4H2NO4). In an analogous manner fulminuric acid is derivable from the type urea (C2 O2 NH) NH3, in which the hydrogen of the ammonia is replaced by the same tribasic radical, C4 H2(NO4). If this view were correct, we ought to get from these compounds evidence of the presence of NO4, and of the group NC4 H2(NO4), which would be mononitroacetonitrile. Schischkoff made the experiment on fulminuric acid, which gave chloropicrine on treatment with hypochlorite of lime, as Kekulé had found was the case with fulminating mercury under the same treatment. Schischkoff found also that fulminuric acid, when treated with nitrosulphuric acid, gave a new body, which is trinitroacetonitrile, NC4(NO4)3. This is a compound similar to camphor, possessing a penetrating unpleasant smell, which melts at 41°.5 and explodes at 220° C. formation may be thus expressed : Its (C2O2NH) (NC4 H2 NO4)+2NO6 H=NC4 (NO4)3 + 2HO+2CO2+NH3. Fulminuric acid. Nitric acid. Trinitro acetonitrile. * Phil. Mag. March 1856. By the action of water and of alkalies, this substance furnishes a body NC4 (NO4)2 (NH4), which is acetonitrile, NC4 H3, in which two equivalents of hydrogen are replaced by 2(NO4), and one of hydrogen by NH4. By boiling this body with potash, and subsequently treating the salt thus obtained with oxide of silver, a beautiful salt is obtained, to which the author gives the formula C4 (NO4)2 (NH4) NHS AGO. This remarkable salt would thus belong A new determination of the equivalent weight of antimony has been made by Dexter*, who has obtained numbers which differ slightly from those obtained by Schneider and by Roset. His determination deserves, however, great consideration, for it was made with all possible care and precision by the method originally used by Berzelius. The starting-point was the preparation of pure metallic antimony; and for the purpose of obtaining this, advantage was taken of the insolubility of metantimoniate of soda. Crystallized tartarized antimony was fused in a Hessian crucible with nitre and potash, and the fused mass poured out, allowed to cool, dissolved and filtered, and a solution of pure chloride of sodium added to it. The metantimoniate of soda precipitated was well washed out, and then converted into hydrated antimonic acid by treatment with nitric acid. The hydrated antimonic acid, well washed out and dried, was placed in a porcelain crucible lined with pure charcoal and strongly ignited. The reduced metal was not quite pure; it contained traces of sodium, for it was impossible to extract all soda from the metantimoniate by nitric acid. The metal was therefore finely powdered, mixed with some of the same antimonic acid, and again strongly ignited. The metal collected at the bottom in a regulus, covered with a slag of melted oxide of antimony. It was quite pure, as was shown by special experiments. Its specific gravity was 6.705 at a temperature of 3°.75. Scheerer for the same temperature found the specific gravity of antimony to be 6·708. For the purpose of the determination, the metal was converted into antimonic acid by treatment with pure nitric acid, the antimonic acid ignited and weighed as antimonious acid, SbO4. The number obtained as the mean of eleven very concordant experiments was 1529.4, or 122-3 on the hydrogen scale. This method of determination, although simple, has the disadvantage that a small error of observation has great influence on the result, and to avoid this source of inaccuracy Dexter made a great many experiments with another method. This consisted in determi* Poggendorff's Annalen, April 1857. + Phil. Mag. February 1857. |