to be in an inverse ratio of the exposed surfaces, as in the former expe riments. Experiment 16. Comparison of a sphere of 7 inches diameter with a circular plate of 14 inches, or double that diameter. In this case the inner and outer surface of the sphere, taken together, are actually the same as the two surfaces of the plate. The inner surface of the sphere being closed, however, as in the last experiment, the surfaces of the sphere and plate, electrically considered, are therefore not equal, and the surface of the plate is twice the surface of the sphere. The surfaces, therefore, open to external induction are as 2: 1. On examining the charges of the plate and sphere, they were found to be as 10: 14, or as 1:14; charge of sphere being 10 circular inches, under an intensity of 20°, and charge of plate being 14 circular inches, under the same intensity of 20°. The charge of the sphere, therefore, as compared with the charge of the plate, is as 1:2, that is, as the square roots of the exposed surfaces. On examining the intensities of the sphere and plate, they were found to be, as in the preceding experiments, in an inverse ratio of the exposed surfaces. We cannot, therefore, conclude, as already observed (4), that the capacity of the plate is twice that of the sphere. 19. The following experiments are further adduced in support of the preceding : Experiment 17. A copper plate 10 inches square, compared with the same plate rolled up into an open hollow cylinder, 10 inches long by 3.2 inches diameter. Here, as in the last experiments, although the surfaces are actually the same, yet, electrically considered, the plate has twice the surface of the cylinder, one surface of the cylinder being shut up. On examining the charges of the cylinder and plate, they were found to be, as in the preceding experiments, as 1:2; that is, as the square roots of the exposed surfaces, and the intensities in an inverse ratio of the surfaces, which seems to be a general law for closed and open surfaces. Experiment 18. A hollow copper cube, side 5.7 inches, surface 195, compared with a hollow copper sphere of diameter equal side of cube, surface 103 square inches nearly. On examining the charges of the sphere and cube, they were found to be as 9: 10 nearly; charge of the sphere being 9 circular inches, under an intensity of 10°, and charge of cube being 10 circular inches, under the same intensity of 10°. The charges of a cube, and of a sphere whose diameter equals the side of the cube, approach each other, notwithstanding the differences of the surfaces, owing to the six surfaces of the cube not being in a disjointed or separated state. 20. The author observes, in conclusion, that the numerical results of the foregoing experiments, although not in every instance mathematically exact, yet upon the whole were so nearly accordant as to leave no doubt as to the law in operation. It would be in fact, he observes, assuming too much to pretend in such delicate experiments to have arrived at nearer approximaions than that of a degree or two of the electrometer, or within quantities ess than that of 25 of a circular inch. If the manipulation, however, be skilfully conducted, and the electrical insulations perfect, it is astonishing how rigidly exact the numerical results generally come out. XX. "On a New Class of Compounds in which Nitrogen is substituted for Hydrogen." By PETER GRIESS, Esq. Communicated by Dr. HOFMANN. Received June 2, 1864. (Abstract.) All the bodies in which nitrogen is substituted for hydrogen which I have discovered during the last few years* may be divided into two distinctly different classes. The first class comprises those bodies which are obtained when three atoms of hydrogen in two atoms of an amido-compound are replaced by one of nitrogen from nitrous acid. The members of the second group are formed by the action of nitrous acid upon one equivalent of an amido-compound only. The following equations will best show these various reactions : I. II. : I have hitherto chiefly examined into the constitution of the bodies that form according to the first equation (diazoamidobenzol, diazoamidobenzoic acid), and have only incidentally explored the field of bodies which equation II. opens up. I have had occasion since to study more closely several representatives of the latter class of compounds, which are derived from aniline (amidobenzol) and analogous organic bases; and since the results which I obtained cannot but excite some interest, I may be permitted to submit them briefly to the Royal Society. Nitrate of Diazobenzol, C, H, N, NHO,. 4 This compound is most readily obtained by passing a rapid current of nitrous acid gas through a solution of nitrate of aniline, saturated in the cold, until aniline ceases to be separated by the addition of solution of caustic potash to the liquid. On diluting the solution then with three times its volume of alcohol, and adding a sufficient quantity of ether, nitrate of diazobenzol separates in long white needles. In order to remove a trace of a colouring substance, the crystals are redissolved in a small quantity of * Ann. der Chem. und Pharm. vol. cxiii. p. 201; vol. cxvii. p. 1; vol. cxxi. p. 257. Proceedings of the Royal Society, vol. x. p. 591; vol. xi. p. 263; vol. xii. p. 418. cold dilute alcohol and precipitated by ether. The following equation expresses the reaction :— C, H.N, NHO,+NHO,=CH_N,, NHO,+2H,O. L. Nitrate of diazobenzol may also be prepared from diazoamidobenzol, a substance described by me on a former occasion*, by treating an etherial solution of the latter with nitrous acid, €12 H11 N2+NHO2+2NHO,=2(C ̧ H ̧ N2, NHO,)+2H2 →. 12 11 Diazoamido benzol. 4 Nitrate of diazobenzol. The new compound dissolves very readily in water, more difficultly in alcohol, and is almost insoluble in ether. On heating, the solutions are decomposed with evolution of gas. The dry substance explodes with the greatest violence when gently heated, and it is necessary to observe great precautions whilst working with it. The chemical analysis could not, for the same reason, be performed by the usual methods. Its composition was, however, readily established by studying the products of decomposition to which boiling with water gives rise, according to the equation C H1 N2, NHO, + H2O=С ̧ H ̧→ + N2 + NHO,. 4 Nitrate of diazo benzol. 6 6 This salt forms when a highly concentrated aqueous solution of the former compound is treated with a sufficient quantity of cold sulphuric acid diluted with its own bulk of water. The solution is treated, as before, with three times its volume of alcohol, and ether added, which causes the sulphate of diazobenzol to separate in a layer of a very concentrated aqueous solution at the bottom of the vessel. On placing this latter solution over sulphuric acid, crystallization ensues after a short time. The crystals are freed from the mother-liquor by washing with absolute alcohol. In this manner large white prisms, which rapidly deliquesce in moist air, are obtained, and which are decomposed with slight deflagration when heated by themselves. Hydrobromate of Diazobenzol, C, H, N, HBr. 4 This compound is obtained in small white soft plates when an etherial solution of diazoamidobenzol is mixed with an etherial solution of bromine, [C12 H1, N2+6 Br=C, H, N2, HBr+ C, H, Br, N+2(HBr). 12 11 3 Diazoamido benzol. 4 Hydrobromate of Tribromaniline. * Ann. der Chem. und Pharm. vol. cxxi. p. 258. Hydrobromate of diazobenzol is very unstable. The beautifully white crystals change so rapidly that in a few moments they acquire a reddish colour, and in a few days the decomposition is almost complete. They explode on heating almost with the same violence as was experienced with nitrate of diazobenzol. Dibromide of Hydrobromate of Diazobenzol, C, H, N2, HBг, Br2. 4 On adding excess of bromine-water to an aqueous solution of any one of the compounds previously described, an orange-coloured oil is obtained which rapily solidifies, after the mother-liquor has been removed, to small orangecoloured plates. The crystals of dibromide are obtained in a perfectly pure state by washing with a little alcohol. This compound is rather difficultly soluble in cold alcohol and ether; and the solutions are rapidly decomposed, particularly on the application of heat. Platinum-salt of the Hydrochlorate of Diazobenzol, C, H, N2, HCl, PtCl. 4 This salt forms beautiful yellow prisms which are almost insoluble in water. The gold-salt, C, H, N., HCl, AuCl,, can be recrystallized from alcohol, and is obtained in very fine golden-yellow brilliant plates. It has thus been sufficiently shown that diazobenzol deports itself like an organic base, being capable, like aniline, of forming salts with various. acids. It possesses, however, also the property of combining with the hydrates of the metals, thus playing the part of a weak acid. Compound of Hydrate of Potassium with Diazobenzol, C, H, N,, KHO. This body is obtained when a concentrated aqueous solution of nitrate of diazobenzol is treated with excess of concentrated aqueous potassa. By evaporating on the water-bath, the liquid solidifies, when sufficiently concentrated, to a magma of yellow crystals consisting of nitre and the compound of hydrate of potassa with diazobenzol. The crystalline mass is pressed between porous stones, and thus partly freed from moisture. By dissolving in absolute alcohol and treating with ether, the new compound of hydrate of potassium with diazobenzol is obtained in a pure state, crystallizing in small soft white plates, which rapidly become reddish, especially in the moist condition. It is very readily soluble in water and alcohol; the solutions, however, decompose slowly, and deposit a reddish amorphous body. Heat does not seem to accelerate this decomposition materially. Compound of Hydrate of Silver with Diazobenzol, C, H, N,, AgHO. This substance is obtained in the form of an almost white precipitate when a solution of silver is added to an aqueous solution of the former compound. It is very stable. Similar compounds are obtained with leadand zinc-salts. Diazobenzol, C, H, N.. This substance is obtained when an aqueous solution of the compound of hydrate of potassium with diazobenzol is neutralized with acetic acid. It separates as a thick yellow oil of very little stability. After a few moments an evolution of gas ensues, and the diazobenzol is rapidly converted into a reddish-brown viscid mass. Diazobenzol is soluble in acids, as well as bases, with formation of the saline compounds previously described. By acting in the cold with aniline upon nitrate of diazobenzol*, the following change takes place : C. HẠN, NHO,+2CH,N=C, H, Ng+C, H, N, NHO. Nitrate of diazo- 3 7 Aniline. Diazoamido- Nitrate of aniline. I was formerly of opinion that diazoamidobenzol must be viewed as a double compound of diazobenzol and aniline. The above equation seems to confirm this view. New compounds analogous to diazobenzol-amidobenzol are obtained by the action of other organic bases upon nitrate of diazobenzol, viz. diazoCH, N12 H benzol-amidobromobenzol, 2 }, (B) N Br 6 by the action of bromaniline. Naphthalidine and nitrate of diazobenzol combine directly and form nitrate of diazobenzol-amidonaphtol, crystallizing in magnificent large green prisms. The action of amido-acids upon nitrate of diazobenzol is analogous to that of the aniline; ex. gr., 4 C ̧H ̧N, NHO ̧+2C,H,NO,= {C, H; N} +C, H, NO, NHO,. Nitrate of diazo benzol. 3 Amido-acid. 7 Diazobenzol-amidobenzoic acid separated quickly as a yellow crystalline mass on mixing the aqueous solutions of both substances. It is purified by recrystallization from ether in the form of small yellow plates. It combines with bases and forms saline bodies. Bichloride of platinum precipitates from an alcoholic solution a yellowish-white crystalline platinum-salt of the composition C,, H1, N, O,, 2HCl, 2 PtCl2. 13 11 Similar double acids to the one just described are obtained by the action of amidodracylic acid, amidoanic acid, &c., upon nitrate of diazobenzol. Imidogen Compounds of Diazobenzol. These peculiar compounds are formed when aqueous ammonia, as well as certain organic bases, are made to act upon the dibromide of diazobenzol. *It is self-evident that for this and similar experiments sulphate and hydrobromate of diazobenzol may also be employed. |