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addition of or of sulphuric acid immediately produces the bright red tint. (Dubail. I. Pharm. 18, 425). Hence boracic acid does not take soda from sulphuric acid or set that acid free. Hydrosulphuric acid and carbonic acid exhibit similar relations towards sulphuric acid. (Dumas.) Tincture of litmus is instantly bleached by chlorine water, but not till after several days by aqueous solution of iodine: now, a solution of chloride of sodium mixed with iodine should, according to Berthollet, produce a mixture containing chloride of sodium with excess of chlorine, and iodide of sodium with excess of iodine. But the orange-yellow mixture colours litmus green (from the yellow of the solution and the blue of the tincture): and a very small quantity of chlorine water immediately changes this green colour into the orange-yellow of the solution of iodive: this shows that no chlorine had been set free by the iodine. (Dubail; Gm.)-Phosphate of peroxide of iron is soluble in hydrochloric acid, but not in acetic acid. From its solution in hydrochloric acid it is completely precipitated by acetate of potash. Now if the potash had been divided between the hydrochloric and acetic acids, part of the hydrochloric acid would have remained free, and would have held some of the phosphate of iron in solution. (Gay-Lussac a. a. 0); also Ann. Chim. Phys. 70, 416.—Compare also Persoz. Chim. molecul. 346.)— The experiments of Soubeiran and 0. Henry (J. Pharm. 11, 430, also Mag. Pharm. 15, 44, also N. Tr. 12, 1, 266) do not prove much in favour of Berthollet's views.
Other objections to Berthollet's theory of distribution may be deduced from the following facts. Oxalate of lead digested with water and as much sulphuric acid as is necessary to saturate the oxide of lead, is completely resolved into sulphate of lead and free oxalic acid. (Pfaff
. Ann. Chim. 77, 266): Berthollet's remarks on this experiment (Ann. Chim. 77, 288,) are not satisfactory.--Hyperiodate of lead digested with water and a quantity of sulphuric acid somewbat less than that required to take up all the oxide of lead, yields a solution of hyperiodic acid free from sulphuric acid and from hyperiodate of lead. (Benckiser. Ann. Pharm. 17, 257.)–Chloride of silver mixed with water is easily converted by iron into metallic silver and chloride of iron, the latter remaining in solution. According to Berthollet the contrary result should be produced, since iron is more coherent than silver, and chloride of silver is insoluble in water, while chloride of iron is soluble. These last experiments likewise show that insoluble substances, such as oxalate of lead, chloride of silver, &c., are by no means removed from the sphere of chemical action.—Similarly Gay-Lussac has shown (Ann. Chim. 89, 21) that a metallic oxide insoluble in water may completely precipitate another from its solution in acids (e. 9., oxide of zinc may precipitate oxide of silver), provided it be added in sufficient quantity to saturate the acid.—3 atoms of iron fused with one atom of tersulphuret of antimony completely separate the antimony from the sulphur, though no solid or gaseous compound is formed, the melted sulphuret of iron lying in a stratum above the melted antimony.
It has also been shown (page 130) that hydrochloric acid decomposes carbonate of lime, and forms with the lime a perfectly neutral solution, even under a pressure sufficient to liquefy carbonic acid. Now since the hydrochlorate of lime is soluble and the carbonate insoluble, the contrary effect ought to be produced, according to Berthollet, as soon as the escape of carbonic acid is prevented. In a similar manner, hydrochloric acid decomposes sulphite of lime, although that salt is nearly insoluble, and sulphurous acid has less elasticity than hydrochloric acid, inasmuch as it is liquefied by smaller pressure.
To Berthollet must be conceded the great merit of having closely scrutinized the theory of affinity, examined it in a new light, and directed attention to the influence exerted by cohesion and elasticity on the manifestations of affinity. But he laid too little stress on the magnitude of affinity, and too much on the quantity in which substances act, and on the influence of cohesion and elasticity. He erroneously supposed that a body which separates in the solid state is removed from the sphere of action, that bodies are capable of combining in all proportions, and that a substance divides itself between two others in the proportion of their chemical masses.
Second Hypothesis. Chemical combinations are produced by a peculiar power, called Affinity, different from universal attraction.
So long as it is assumed that universal attraction, as manifested in gravitation, acts only in proportion to the mass, and that the peculiar nature of a substance has no influence on its amount,-it is difficult to refer the manifestations of cohesion and adhesion, and impossible to attribute those of affinity, to its action. In chemical phenomena, the quality of a substance above all things determines the existence and strength of the attraction, and its influence cannot be replaced by that of quantity. Moreover, a high degree of affinity must be ascribed to the imponderable bodies, which are not subject to the laws of gravitation. So long therefore as it shall remain undemonstrated that gravitation is influenced by quality of matter, and that the hitherto so-called Imponderables possess weight,-- or else that the phenomena hitherto attributed to the affinities of these bodies are really due to other causes—so long will it be most advisable (as indeed most chemists at least tacitly do) to regard affinity as a peculiar power distinct from all others.
Third Hypothesis. The union of heterogeneous atoms is the result of Electrical Attraction. (Electrochemical Theories).
In some of these theories a common fundamental power is assumed which shows itself, sometimes as electrical, sometimes as chemical force; in others the combinations of ponderable substances, uninfluenced by any affinity of their own, are supposed to arise merely from the mutual attraction of the two electricities attached to their atoms, which attraction is itself regarded as a kind of affinity.
To the list of electro-chemical theories belong those of Winterl (N. Gehl. 6, 1 and 201);-of Sir H. Davy (N. Gehl. 5, 41, also Elem. of the Chemical Part of Nat. Phil.);-of Dumas (Phil. of Chem. p. 369), further developed and contested by Grotthuss (Phys. Chem. Investigations, 1, 44);-of Ampère (Pogg. 2, 185);-of Becquerel (Ann. Chim. Phys. 24, 192);—of Ferré (Ann. Chim. Phys. 28, 417);-of Schweigger (Schw. 5, 49; 6, 250; 7, 302 and 515; 8, 307; 11, 54, 330 and 435; 14, 510; 25, 158; 39, 214; 40, 9; 44, 79; 52, 67);—and of Fechner (Schw. 52, 27).
The electro-chemical theory of Berzelius demands, as the fullest and most consecutive, a more detailed explanation.-Compounds usually called chemical are divided into two classes. The less intimate whose formation is attended with lowering of temperature-.g. solutions of salts in water-must be regarded (since all solid bodies are not soluble in water) as resulting from a specific attraction (comp. page 34 1, 2); the atoms of the solid body diffuse themselves through the liquid, till each atom is surrounded by an equal number of atoms of the liquid. — The more intimate compounds are the really chemical or electro-chemical combinations. These result, not from any mutual affinity between their ponderable elements, but from that of the electricities attached to their atoms. The atom of each substance has two poles, on which the two opposite electricities
are accumulated in different proportions, according to the nature of the bodies. The atom of many bodies, oxygen for instance, has a large quantity of negative electricity attached to one of its poles, and but a very small quantity of positive electricity at the other; that of other bodies potassium for example, has a large quantity of positive electricity at one pole and very little negative electricity at the other. Thus the elementary substances are divided into electro-negative and electro-positive. To each element however there belongs a particular proportion between the quantities of the two electricities. Oxygen has, of all the electronegative elements, the greatest quantity of negative electricity at one of its poles and the smallest quantity of positive electricity at the otherthen follows sulphur, then nitrogen, &c., and lastly hydrogen, in which the quantities of the two electricities are nearly equal. Of all electropositive substances, potassium has the largest quantity of positive and the smallest of negative electricity; and this inequality continually diminishes in other bodies, till we come to gold, in which the positive electricity predominates but little over the negative—so that this element occupies the next place to hydrogen. According to this, the elements succeed one another in the electro-chemical series of Berzelius as follows, beginning with the electro-negative.
Electro-negative: 0, S, N, F, Cl, Br, I, Se, P, As, Cr, V, Mo, W, B, C, Sb, Te, Ta, Ti, Si, H.
Electro-positive: Au, Os, Ir, Pt, Rh, Pd, Hg, Ag, Cu, U, Bi, Sn, Pb, Cd, Co, Ni, Fe, Zn, Mn, Ce, Th, Zr, Al, Y, G, Mg, Ca, Sr, Ba, L, Na, K.
In the combination of an electro-negative with an electro-positive body, the predominant negative electricity of the former unites with the predominant positive electricity of the latter. Before, however, combination takes place, the former substance exhibits negative, and the latter positive electricity in the free state; and the tension of the two electricities continually increases as the bodies approach the temperature at which combination takes place. Hence we have an explanation of electricity by contact. At the instant of combination, the negative poles of the atoms of the first body turn themselves towards the positive poles of those of the second; and since it is only in the fluid state that the atoms possess the mobility necessary for this arrangement, it follows that solid bodies bave, generally speaking, no chemical action on one another. The two electricities of these poles now combine and produce heat or fire, whereupon they disappear. In every chemical combination, therefore, a neutralization of the opposite electricities takes place, by which heat or fire is produced in the same manner as in the discharge of the electrical pile or of lightning, excepting that these last-mentioned phenomena are not accompanied by any chemical combination, at least of ponderable bodies. Every chemical combination is therefore an electrical phenomenon depending on the electrical polarity of the atoms.
Since the electrical series does not accord with the order of affinitysince for example, the highly electro-negative substance oxygen has, according to experiment, less tendency to combine with the electro-positive body gold than with sulphur which stands next to oxygen in the electrical series—Berzelius supposes that, although in the atom of gold the positive electricity of the one pole is of greater amount than the negative electrity of the other, nevertheless the absolute quantity of positive electricity existing at one pole of the atom of gold is less than that which is present at one pole of the atom of sulphur,—the latter containing however a much greater quantity of negative electricity at its other pole than the gold-atom possesses. Suppose for instance that the quantity of negative electricity at one pole of the gold-atom = 1, of the positive electricity at the other = 2, of the negative at one pole of the sulphur-atom = 12, and that of the positive at the other pole = 4; then the positive electricity will predominate in the goldatom and the negative in the sulphur, but the sulphur will possess a much higher degree of electrical polarization than the gold; the positive electricity accumulated at its positive pole will therefore be able to neutralize a greater quantity of negative electricity in the oxygen than the positive electricity of the gold; hence the greater tendency of oxygen to combine with sulphur than with gold.
In the same body, the degree of electrical polarisation,-i.e. the absolute quantity of the two electricities in the atomic poles-varies, according to Berzelius, with the temperature, and is generally increased by elevation of temperature. Many bodies, such as carbon, which appear to have but very weak polarisation at common temperatures, often become highly polarized at a red heat,—hence their combination with oxygen at that temperature. Many substances, on the contrary, such as gold, which have altogether but weak polarization, frequently show it in a greater degree at low than at high temperatures, at which indeed it often disappears entirely.
Electro-negative bodies in combination with oxygen generally form electro-negative compounds; e. g. sulphur produces sulphuric acid; electro-positive substances give electro-positive compounds; e.g. potassium produces potash.
The decomposition of a compound produced by electro-chemical neutralization can only take place when the elements have their former polarity restored to them. That the united elements, after the neutralization of their opposite electrical states, are held together by a force which resists all mechanical means of separation, does not result from any innate power (affinity); otherwise the permanence of the combination would not be subject to the influence of electricity. But the most intimate chemical combination may be destroyed by restoring the electrical polarity of the elements. In this decomposition of compounds by the electrical current, the acting electricities disappear and the elements reassume their former chemical and electrical properties. If A B is resolved by Cinto A C and B, C must have greater intensity of electrical polarization than B. Hence there results more complete neutralization between A and C than that which before existed between A and B; this gives rise to development of heat, and B reappears with its original polarity. A substance capable of combining with others, sometimes as an electro-positive sometimes as an electro-negative element, can only be separated from the first mentioned combinations by bodies still more positive, and from the latter by bodies still more negative: e.g. sulphur can only be separated from its combinations with oxygen by bodies which are more positive, and from its combination with lead by bodies which are more negative than itself.
This theory of Berzelins is encumbered with the following difficulties: -(1). No precise demarcation can be drawn between the less intimate chemical combinations supposed to be produced by affinity and the more intimate ones which are ascribed to electrical action. At all events it does not seem conformable to nature to assume the existence of two totally different causes for these two very similar classes of compounds. According to this view, oue atom of sulphuric acid should combine with the first two or three atoms of water, not by affinity but by electrical attraction,
and with any further quantity of water by affinity. Now if sulphuric acid combined with three atoms of water, possess affinity for water, why should not the same acid when pure or when combined with one atom of water, also have affinity for water?—(2). What is it that induces the two electricities to accumulate each by itself in definite quantity, on two opposite points of an atom which must be regarded as a homogeneous mass? What prevents their combination? Are the atoms of all bodies, even of metals, perfect non-conductors? Again, when sulphur and lead are melted together, the negative electricity of the sulphur-atoms is supposed by Berzelius to combine with the positive electricity of the leadatoms, the combination being accompanied by a development of light and heat. Why does not the negative electricity at one pole of an atom of sulphur combine with the positive electricity at the opposite pole of another atom and produce fire, when the sulphur is melted by itself ?(3). If combinations are produced not by the affinity of the elements but by electrical polarity, every substance, simple or compound, should be capable of combining with every other whose atomic poles contain the two electricities in different proportions; why, for example, should the predominating positive electricity of mercury combine with the negative electricity of tellurium and not with that of carbon ?—(4). It is not easy to discover by what force combined substances are held together. The heterogeneous atoms unite in consequence of their adhesion to the opposite electricities; but when these have been neutralized by combination, it might be expected that the atoms would fall asunder and allow themselves to be easily separated by friction and other mechanical forces, which is by no means the case. In order to overcome this difficulty, Dumas supposes (Philos. of Chem.) that in the combination of oxygen and hydrogen, for example, the negative pole of the former places itself towards the positive pole of the latter, and the positive pole of the former towards the negative pole of the latter; moreover, that the atoms can only give np the electricity of one of their poles—that it is only on this side that electrical neutralization takes place, viz., of the negative electricity of the oxygen with the positive of the hydrogen—that on the contrary the electricities of the two other poles, viz., the positive of the oxygen and the negative of the hydrogen remain uncombined, and hold the atoms united by their mutual attraction. But this assumption—that the electricity of only one pole of an atom can combine with the opposite electricity of another, and that those of the other poles are incapable of uniting—would not only be a new enigma, but admits of positive contradiction; for in the combination of sulphur with oxygen, the positive electricity of the sulphur must unite with the negative of the oxygen; and in the combination of sulphur with the metals, its negative electricity with the positive of the metal. Einbrodt's explanation (Ann. Chim. Phys. 61, 262; also J. pr. Chem. 8, 345,) agrees in the main with that of Dumas.
The theory adopted in the present work is as follows:-Ponderable bodies have affinity for one anotter. The two electricities are substances which likewise possess affinity for each other, and by whose combination in the proportions in which they neutralize each other, heat (fire) is produced. The individual electricities, and likewise heat, have considerable affinity for ponderable substances, and are united to them with greater force and in greater quantity, the more simple these ponderable substances are. Ponderable bodies, according to their nature, have a greater or less excess of positive or negative electricity united with them in addition to a definite quantity of heat. Thus, oxygen probably contains the greatest