As an application of this idea to bibasic compounds, sulphuric acid(SH, O,) is to be regarded as water in which SHO, replaces H, thus ((SHO,)H)O. As the replacing elements contain an equivalent of hydrogen which is saline, the acid is bibasic. When the hydrogen in SHO, is replaced by a metal we have a class of acid sulphates as (( SKO,) H)0. The complete replacement of hydrogen in the original type gives rise to (SHO ̧),O= S, H, O,, which is the Nordhausen acid commonly represented by 2SO,, HO. This latter compound as M. Gerhardt has shown corresponds to the anhydrous bisulphate of potash. 2 The tribasic acids may equally be reduced to the same type if we conceive the elements which replace one equivalent of hydrogen to be bibasic instead of indifferent or monobasic. Phosphoric acid PH, O, is ((PH, O,H)O. 4 3 The primitive saline type is then essentially bibasic, and is presented in its most elemental form in water, while the simplest type of the monobasic salt which is a derivative of the last, is found in hypochlorous acid. The ideas above announced show that it is possible to develop some connection between a series of compounds hitherto regarded as widely distinct from each other, and may lead us to hope that the time is coming when a new day will dawn upon the science. M. Laurent proposes a view of elementary bodies that shall divide them into two classes, which he designates as The vertical groups represent those bodies which are equivalent to each other and may be again divided into isomorphous groups. These elements may exist in any number of equivalents in organic bodies, but the sum of those of the second group, in accordance with his well known law,* will always be divisible by *As this important law which was first fully announced in the essay of M. Laurent, before quoted, may not be familiar to all our readers, we translate entire that portion of his memoir. "M. Gerhardt has endeavored to show that in a regular notation, the number of atoms of each element ought to be a pair, and that moreover in those combinations which do not contain azote, the number of atoms two. The reason of this will appear if we conceive the equivalents of the elements like those of their compounds, to be represented by 2 volumes; we have then, "The molecules of hydrogen, of chlorine and indeed all the diodides, are formed of two atoms which constitute a homogeneous combination, (HH), (Cl Cl), (MM), etc. These in the presence of each other can undergo a double decomposition or mutual substitution and form a heterogeneous combination." "(HH)+(CI CI)=(HCI)+(Cl H) (MM)+(CI CI)=(MC1)+(C1 M). of hydrogen should be divisible by 4. In searching to explain the introduction of azote into organic bodies, I have been led to complete the rule of M. Gerhardt and to apply to azotized compounds the following proposition. In all azotized substances, represented by 4 volumes, the sum of the atoms of hydrogen and azote is always a multiple of 4.' From this proposition the following corollaries are deducible: 1st. If the hydrogen becomes 0, the number of the atoms of azote is a multiple of 4. 2d. If the azote becomes 0, the number of the atoms of hydrogen is a multiple of 4.-(Gerhardt.) 3d. If the organic substance contains phosphorus or arsenic in place of azote, the same rule is observed. 4th. The halogen bodies (Cl, Br, I,) may be substituted for the hydrogen, but the sum of the azote, the hydrogen and the halogen bodies is still a multiple of 4; it results from this that an organic substance cannot combine with two, six or ten volumes of chlorine, bromine, etc. 5th. The metals which form oxyds (R, O) corresponding to water (H 2 O), also replace hydrogen, and observe in their combinations the same rule. 6th. The metals of the oxyds, R4 03 (R, O3 in the ordinary notation), do not replace hydrogen, equivalent for equivalent; and it follows that in all the combinations which correspond to these oxyds, the sum of the atoms of hydrogen, of the metals, of azote, etc., is not divisible by 4." "In a notation which corresponds to two volumes, the preceding numbers must be divided by 2. On account of the simplicity of the formulas, I give preference with M. Gerhardt to this second notation. Our two propositions then unite into the following. In all organic substances, the sum of the atoms of the hydrogen, azote, phosphorus, arsenic, the metals and the halogen bodies, ought to be divisible by 2." In regard to the truth of this law, it is to be remarked that among the hundreds of combinations where our position and equivalent is well determined, there is not a single exception, and that the few apparent ones principally among the organic alkaloids, have nearly all been explained by new and carefully conducted analyses, which have shown in their formulas a perfect conformity. 3 The fifth corollary may be made to include the sixth, by a simple hypothesis, which M. Laurent has proposed in the Revue Scientifique. As MO, corresponds to 3H, O, and consequently M4 to H ̧, it is obvious that MH; and regarding the metals in these oxyds as uniting in two-thirds of their ordinary equivalents, they will no longer be exceptions, but will be included in the fifth corollary. See this Journal for Sept., 1847." (Review of Gerhardt.) "The molecules of the monasides may also divide in two, but the half of the molecule does not necessarily require a complementary half to form a combination. This half can unite itself with an entire diodide. (HH)+(HH)+(00)=(HH)0+(HH)O, or with an entire monaside, (CC)+(CC)+(00)=(CC)0+(CC)O, or with the half of a monaside, (CC)+(00)=(CO)+(CO).” "If instead of taking one volume for some bodies, two for others and four for others as is ordinarily done; or if in place of taking with M. Gerhardt one volume for simple bodies and two for compounds, we represent all bodies whether simple or compound by one volume, we have a much more regular notation and one which taken in connection with the preceding ideas, enables us to represent the formulas of all bodies, without employing fractional numbers." "We admit that each molecule of the simple bodies is at least divisible into two parts which we designate atoms; the molecules can only be divided in case of combination, we have then Oxygen, Hydrogen, Water, 0,=200·0 2 Hydrochloric acid, HCl=227-0 "Each letter O, H, Cl represents a demi-volume or demi-molecule or one atom. The formula of all these bodies indicates immediately the condensation. In no case do I change the notation of M. Gerhardt. "The atom of M. Gerhardt represents the smallest quantity of a simple body which can exist in a combination. My molecule represents the smallest quantity of a simple body which can be employed to effect a combination, a quantity which is divided into two parts by the very act of combination. For example, Cl can enter into combination, but to effect this it is necessary to employ Cl. I admit then with M. Ampère the double decomposition of chlorine by hydrogen and the divisibility of atoms; I admit moreover for hybrids, a divisibility to which I assign no limits." "From my propositions a curious consequence is deducible; M. Gerhardt has remarked that it is impossible that the nitric and chloracetic acids can contain water, because the formulas of these three bodies are NHO,, C, HCl, O, and H, O. It will be seen that this difficulty is not avoided by adopting the ordinary formulas, N,O,+H,O and C, Cl, O,, H2O, for it will then be necessary to represent water by H, O,. 5 2 4 "I believe that we may go farther and not only say that the hydrogen is not combined with oxygen, in the nitric acid, but that it is combined with azote, the two atoms of these bodies being complementary to each other. Taking one volume which for the simple bodies represents one molecule or two atoms: This last hypothesis I present as one of the deductions of the author from his views, but it seems to me hardly warranted. The following application of the idea of the binary arrangement of atoms to the explanation of the affinities exhibited by bodies in the nascent state, is very beautiful and ingenious. "If we place together two free molecules of bromine and hydrogen (BB') and (HH'), the affinity of B for B' and of H for H' will perhaps be sufficient to oppose the combination of B and B' with H and H', but if only B and H were present, these two atoms not having to overcome any affinity would readily combine. This is what takes place, for example, if hydrogen is in the nascent state, as when we decompose hydrochloric acid by a metal, for we have HC1+M=CIM+H, which tends to reconstitute itself into a binary molecule by combining either with bromine or another molecule of hydrogen." "With sulphuric acid SH, O, and a metal, the reaction is the same and the hydrogen is nascent or atomic, for it first forms an acid salt, eliminating H and not (HH); when the acid salt is formed, the second atom will be in its turn disengaged." 5 4 The binary molecule of the metals, hydrogen, chlorine, bromine, &c., will be seen to be the type of an immense number of combinations embracing the various alloys and amalgams, the hydracids like hydrochloric acid and their corresponding salts and such compounds as Cl Br and Cl I. The compound represented by ICI, is referable to a triple molecule of these elements represented by H6 or (HHHHHH); to this same type belong the perchlorids of antimony, arsenic and phosphorus, while the corresponding trichlorids form a double molecule. In all of these it will be observed that the molecular composition is preserved inviolate, all of the inorganic compounds into which the second group of elements enter, furnish a sum of atoms divisible by 2. In the oxygenized bodies on the contrary, we have a type which is composed of three atoms. M. Laurent's law is thus seen to be equally applicable to other compounds, than those denominated organic. I have thrown out a few ideas suggested by this memoir of M. Laurent, and have at the same time pointed out the basis upon which it appears to me a true natural system of chemical classification can be founded. Imperfect as they are, I hope they may not prove unworthy of the consideration of scientific men, and tend to forward the progress of chemical philosophy. ART. XIV.-Upon the Influence of Color on Dew; by Prof. JOHN BROCKLESBY. In those beautifully accurate experiments, from which Dr. Wells derived his theory of dew, the influence of various material properties, in determining the amount of moisture deposited upon bodies, under like exposures, is clearly and satisfactorily unfolded. We are howeyer left to regret, that this sagacious observer did not illustrate the effect of color, by a full course of experiments. This subject indeed was not entirely omitted. In four out of five experiments, made with parcels of black and white wool, alike in size and weight, he discovered that the former had gained a little more dew than the latter; but as the fibres of the white wool were somewhat coarser than those of the black, he accounts for the entire difference in the quantities of moisture from this circumstance alone. At another time he exposed a piece of pasteboard covered with white paper, and close to this a second piece, similar in every respect to the first, covered with paper blackened with ink. In the morning he beheld hoar-frost upon both the cards, but the black surface appeared to have gained a greater quantity than the white. A doubt however rose in the mind of the observer upon this point, inasmuch as from the contrast of color the amount of hoarfrost might have been apparently greater upon the dark than upon the light surface even when no real difference existed* in favor of the black. Influenced by certain views in regard to the effect of the chemical constitution of bodies in modifying radiation, Dr. Welles pursued this inquiry no farther. The subject here rested until the year 1833, when Dr. Stark of Edinburg instituted a series of experiments to determine the influence of color upon heat, odors and dew.† Two experiments * This appearance I have frequently observed, when the amount of dew upon the white exceeded that upon the black. t In 1835, Prof. Bache of the University of Pennsylvania, investigated the influence of color upon the radiation of non-luminous heat. His experiments were |