The Second Step in Chemistry, Or the Student's Guide to the Higher Branches of the Science

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J. Churchill, 1864 - 774 páginas

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Página 489 - When the formulae of inorganic chemical compounds are considered, even a superficial observer is struck with the general symmetry of their construction ; the compounds of nitrogen, phosphorus, antimony, and arsenic especially exhibit the tendency of these elements to form compounds containing...
Página 693 - The colloidal is, in fact, a dynamical state of matter, the crystalloidal being the statical condition. The colloid possesses Energia. It may be looked upon as the probable primary source of the force appearing in the phenomena of vitality. To the gradual manner in which colloidal changes take place (for they always demand time as an element) may the characteristic protraction of chemico-organic changes also be referred.
Página 198 - A very valuable use of electro-chemical equivalents will be to decide, in cases of doubt, what is the true chemical equivalent, or definite proportional, or atomic number of a body ; for I have such conviction that the power which governs electro-decomposition and ordinary chemical attractions is the same...
Página 198 - I have such conviction that the power which governs electro-decomposition and ordinary chemical attractions is the same ; and such confidence in the overruling influence of those natural laws which render the former definite, as to feel no hesitation in believing that the latter must submit to them also.
Página 692 - Another and eminently characteristic quality of colloids is their mutability. Their existence is a continued metastasis. A colloid may be compared in this respect to water while existing liquid at a temperature under its usual freezing point, or to a supersaturated saline solution.
Página 690 - While soluble crystalloids are always highly sapid, soluble colloids are singularly insipid. It may be questioned whether a colloid, when tasted, ever reaches the sentient extremities of the nerves of the palate, as the latter are probably protected by a colloidal membrane, impermeable to soluble substances of the same physical constitution.
Página 692 - The inquiry suggests itself whether the colloid molecule may not be constituted by the grouping together of a number of smaller crystalloid molecules, and whether the basis of colloidality may not really be this composite character of the molecule.
Página 141 - Mercuric iodide separates from solution, and likewise sublimes at a very gentle heat, in scarlet tables belonging to the dimetric system; but when sublimed at a higher temperature in sulphur-yellow, rhombic tables of the monoclinic system. The red crystals turn yellow when heated, and resume their red tint on cooling. The yellow crystals obtained by sublimation retain their colour when cooled ; but, on the slightest rubbing or stirring with a pointed instrument, the part which is touched turns scarlet,...
Página 690 - A certain parallelism is maintained between the two classes, notwithstanding their differences. The phenomena of the solution of a salt or crystalloid probably all appear in the solution of a colloid, but greatly reduced in degree. The process becomes slow; time, indeed, appearing essential to all colloidal changes. The change of temperature, usually occurring in the act of solution, becomes barely perceptible.
Página 690 - It has been observed that vegetable gum is not digested in the stomach. The coats of that organ dialyse the soluble food, absorbing crystalloids and rejecting all colloids. This action appears to be aided by the thick coating of mucus which usually lines the stomach. The secretion of free hydrochloric acid during digestion — at times most abundant — appears to depend upon processes of which no distinct conception has been formed. But certain colloidal decompositions are equally inexplicable upon...

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