The question naturally suggested itself, whether the same acid could not be prepared directly from the hydrocarbon benzol. Mitscherlich has already described an acid (the sulphobenzolic) in which one equivalent of that hydrocarbon is associated with one equivalent of bibasic sulphuric acid. We have proved by experiment that sulphobenzolic acid takes up the elements of an additional equivalent when it is submitted to the prolonged action of Nordhausen sulphuric acid, and that, in fact, the union of these two bodies presents the most ready method of procuring disulphobenzolic acid in a state of purity. The preceding researches establish in two different groups of bodies the existence of a series of bibasic acids containing four equivalents of sulphur, and which, irrespectively of any special view regarding their molecular arrangement, may be represented as formed by the association of the hydrocarbon (corresponding to marsh-gas) of the various groups with four equivalents of anhydrous sulphuric acid, Disulphometholic acid.... Disulphobenzolic acid 8 An acid of analogous composition exists in the naphthalin-series, disulphonaphtholic acid, C20 H 4SO3, which was discovered by Berzelius, and subsequently studied by Laurent. Many of these substances may be actually obtained directly from the hydrocarbons by the action of sulphuric acid. On the other hand, chemists are well acquainted with the deportment of olefiant gas under the influence of anhydrous sulphuric acid. The crystalline compound discovered by Magnus, and described by him under the name of sulphate of carbyl, whatever its constitution may be, can be considered as a direct combination of olefiant gas, with four equivalents of anhydrous sulphuric acid, Sulphate of carbyl........ C, H, 4SO.. It can scarcely be doubted that all the other hydrocarbons, Cn2 H2, propylene, butylene, amylene, &c., will furnish homologous substances. Sulphate of carbyl, when submitted to the action of water, assimi lates two equivalents, and is converted into a bibasic acid (ethionic), CH, 4SO +2HO=C, HI, O, 4SO, which accordingly may be viewed as an association of alcohol with four equivalents of anhydrous sulphuric acid. Terms analogous to ethionic acid are sure to be found when the study of the homologues of sulphate of carbyl shall be taken up by chemists. The production of disulpho-compounds of perfectly similar composition, from substances belonging to such different groups of bodies, as the hydrocarbons homologous and analogous to marsh-gas, ethylene and alcohol, suggested the possibility that the substances in question might be but individual examples illustrating a far more general mode of formation. It became, in fact, probable that all organic bodies capable of uniting with the elements of two equivalents of anhydrous sulphuric acid might, under favourable circumstances, be induced to assimilate two additional equivalents of anhydrous sulphuric acid, and thus furnish other terms belonging to the class of disulpho-compounds. The only additional class of compounds to which we have as yet successfully extended our labours, is the group of organic bases.. Action of Sulphuric Acid upon Aniline. The first product which sulphuric acid forms with aniline is simply the sulphate of the base. A further addition of acid, assisted by heat, dissolves the sulphate, and after a sufficiently long digestion, the whole is converted into sulphanilic acid. If too high a temperature be employed, the acid becomes very dark in colour; and indeed there is a limit beyond which carbon is rapidly deposited, accompanied by the evolution of abundance of sulphuric acid. The process of converting sulphanilic acid into the disulpho-compound is rather tedious. It may, however, be effected without fail, by treating for several hours the perfectly dry crystalline acid, mixed with strong Nordhausen acid, to the consistence of a paste. The heat should not exceed that at which sulphurous acid just commences to be evolved. We employed an air-bath heated from 160° to 170° C., and the digestion was continued until a portion removed by a glass rod showed no trace of crystallization when cooled or moistened with water. Treatment with carbonate of barium yielded in this manner a very soluble salt, which furnished a brittle gum when evaporated. The new substance was precipitated from its solution by alcohol and dried at 200° C. A determination of the barium and the sulphur led to the expression C12 (H, Ba2) N SO129 which is the formula of disulphanilate of barium. This salt is readily attacked by concentrated nitric acid with oxidation of the sulphur. It blackens when strongly heated on platinum foil, and yields sulphurous acid without inflaming, a deportment in which it differs from sulphanilate of barium, which burns with a bright flame. When heated in close vessels it forms a crystalline sublimate, which consists of sulphite of aniline. Disulphanilic acid is prepared by decomposing the lead-salt with hydrosulphuric acid. It is very soluble in water, and crystallizes with difficulty. It may be precipitated from a strong aqueous solution by alcohol in the form of white grains. The precipitation is assisted by the addition of a little ether. It has a very rough and acid taste. We have also prepared the silver-salt by saturating the acid with carbonate of silver. The most ready method of obtaining it in a solid state is by precipitation with alcohol and ether. The aqueous solution, by concentration, deposits a black powder which makes it very difficult to obtain the crystals colourless. The formula of disulphanilate of silver is C12 (H5 Ag2) N SO12. The potassa-salt is crystalline. It forms small grains or minute needles, which are insoluble in alcohol. The researches detailed in the preceding paragraphs may serve to characterize more fully a class of compounds of which only a few terms, isolated and scattered in widely different groups, had been previously observed. The only disulpho-acids hitherto known, are Berzelius's and Laurent's disulphonaphthalic acid, Magnus's ethionic (disulphethylic) acid, and lastly, dithiobenzic acid, recently discovered by M. Kilkenkamp. To these we now add five new acids, belonging to several of the most important series of compounds : Our experiments point out, moreover, the universal occurrence, and the general mode of formation of these substances. All organic molecules, particularly in the nascent state, appear to be capable of assimilating the elements of either two or four equivalents of anhydrous acid. The formation of the two groups of acids which are thus produced presents a great analogy with the production of the nitro-substitutes generated under the influence of nitric acid. All these compounds are generated with the elimination of water. In the action of nitric and sulphuric acid upon benzol, for instance, we have, The analogy of these reactions is obvious. The action of nitric acid upon organic bodies is by no means limited to the production of nitro-compounds corresponding to nitrobenzol and dinitrobenzol; frequently additional substitutes are formed with elimination of six, eight, and in a few isolated cases, even of ten equivalents of water. It is possible that analogous sulpho-compounds may exist. Hitherto, however, no substances have been observed in which the assimilation of sulphuric acid has gone further than in the disulpho-acids. VI. "On Quantitative Measurement in Statical Electricity, and on some new Phenomena of Electrical Force." By Sir WILLIAM SNOW HARRIS, F.R.S. Received June 12, 1856. (Abstract.) The author observes, that number, weight, and measure are the foundation of all exact science, and that, as expressed by an eminent and learned writer (M. Quetelet), no branch of human knowledge can be held as being out of its infancy which does not in some way or the other frame its theories or correct its practice by reference to those elements; he was hence led to seek and establish such rigorous and exact quantitative processes in common electricity as would measure the quantity of electricity in operation; its attractive or repulsive force under given conditions, and its dynamical or current force when traversing bodies under the form of electrical discharge. The instruments which he has invented for this purpose have been all honoured by a place in the Philosophical Transactions of the Royal Society. They amount to five in number, viz. the Unit Measure, the Balance and Hydrostatic Electrometers, the Thermo-electrometer, and the Bifilar Balance. In referring to such of these instruments as are employed in the present research, the author briefly adverts to their general construction, including the latest and best form under which they have been placed. In the measurement of quantity, he considers the unit measure as being the best and most accurate means of estimating quantity as yet arrived at ; and he describes a series of crucial experiments, the object of which is to show that the unit explosions are rigorously exact. If an electrical jar exposing about 5 square feet of coated surface be insulated, and a second equal and similar jar be so placed as to charge from its outer coating, and if the first jar be charged from the conductor of the machine through the unit measure, it is found by a Lane's discharging electrometer attached to each jar, that an equal number of measures are given off from the outer coating of the insulated jar at all periods of the progress of the charge. Thus, whether the first jar be charged with 20, or 40, or 60 measures, |