Hydrate

“ Journ., (3) 1, p. 703) , or by hydrolysis with a known volume of standard alkali and back titration with standard acid (V. Meyer, Ber., 1873, 6, p. 600) . Chloral hydrate has the property of checking the decomposition of a great number 254 of albuminous substances, such as milk and meat; and a mixture of it with glycerin, according to J. Personne, is suitable for the preservation of anatomical preparations. When heated with concentrated glycerin to a temperature of 110° to 230° C, chloral hydrate yields chloroform, CHCl3, and allyl formate, HCO (OC3H5) . ”

“ Intermediate hydrates exist, but they are more soluble, and cannot be readily isolated. Both the mono- and hexahydrates are capable of existing in equilibrium with saturated solutions at temperatures far below their transition points, provided that the less soluble hydrate is not present in the crystalline form. The solubility curves can therefore be traced, as in fig. 3, over an extended range of temperature. The equilibrium of each hydrate with the solvent, considered separately, would present a diagram of two branches similar to fig. ”

“ Although ferric chloride and water form the largest and best-studied series of hydrates possessing definite melting points, examples of similar hydrates are not few in number; and more careful investigation is constantly adding to the list. [234] In all these cases the solubility curve will show a point of maximum temperature, at which the hydrate melts, and will end, above and below, in a cryohydric point. Conversely, if such a curve is found in a system of two components, we can argue that a definite compound of the components possessing a definite melting point is formed. ”

“ The moist hydrate is used in several processes in the arts. It is the base of cobalt-blue, the lake-pigments, &c. In medicine, it is employed as an antacid and astringent, in acidity of the stomach, cholera, diarrhœa, and dysentery; in which it is said to be superior to the other absorbent remedies. (Ficinus.) It has also been highly recommended in the vomiting and diarrhœa of infancy. (Durr; Neumann; Weese; &c.) —Dose. Children 3 to 10 gr.; adults, 5 or 6 to 20 or even 30 gr., three to six times daily, suspended in water, by mucilage or simple syrup. ”

“ Hot Water and Salt for.—A teaspoonful of salt in a pint of hot water is good also, used as a spray, or to inhale. But the patient must lie down.
6. Other Easily Obtained Remedies.—Ergot in dose of one-half to one teaspoonful is very good; this contracts the vessels. Bromide of potash in a dose of five to fifteen grains; or chloral hydrate in dose of five to seven grains, if there is not heart trouble. If there is, chloral hydrate cannot be used. These quiet the nervous system and do much good. Strong hop tea will do the same thing if taken freely. ”

“ According to Proust, this hydrate contains 20 or 21 per cent. water. If we suppose the blue to be 1 atom oxide, and 1 water, the yellow hydrate may be 1 water and 2 of the proto-hydrate; or 88 oxide, and 24 water, which will be nearly 21 per cent. water.
The black oxide gives out oxygen gas by a red heat, and is reduced to the grey oxide: it forms oxymuriatic acid, with muriatic acid, and the protoxide remains in solution. ”

“ A salt hydrate in contact with vapour constitutes only a bivariant system, and can exist therefore at different values of temperature and pressure of vapour, as is seen from the diagram, Fig. 19. Anhydrous copper sulphate can exist in contact with water vapour at all values of temperature and pressure lying in the field below the curve OC; and the hydrate CuSO4,H2O can exist in contact with vapour at all values of temperature and pressure in the field BOC. Similarly, each of the other hydrates can exist in contact with vapour at different values of temperature and pressure. ”

“ This oxide has not yet been obtained in a satisfactory manner, but the hydrate is prepared by the addition of potassium463 hydrate solution to a solution of chromous chloride or sulphate. A brownish-red powder, speedily passing to a deep foxy-red, with disengagement of hydrogen, and forming pale blue-coloured salts with the acids, which absorb oxygen with avidity, whilst the metal passes into a higher state of oxidation. ”

“ Hydrate of alumina is an instance in question, which is soluble both in caustic potash and in sulphuric acid.
The degree of affinity or chemical energy proper to oxides and their hydrates is very dissimilar; some extreme members of the series possess it to a great extent. When acting on each other they evolve a large quantity of heat, and when acting on intermediate hydrates they also evolve heat to a considerable degree, as we saw in the combination of lime and sulphuric anhydride with water. ”

“ Chloral hydrate completely volatilises, and can be distilled in a vacuum without change. If, however, boiled in air, it undergoes slow decomposition, the first portions of the distillate being overhydrated, the last underhydrated; the boiling-point, therefore, undergoes a continuous rise. The amount of hydration of a commercial sample is of practical importance; if too much water is present, the chloral deliquesces, especially in warm weather; if too little, it may become acid, and in part insoluble from the formation of meta-chloral (C6H3Cl9O3) . ”

“ Various examples of this behaviour are known, and we choose for illustration the solubility relationships of barium acetate and its hydrates [222] (Fig. 36) .
Fig. 36.
At temperatures above 0°, barium acetate can form two stable hydrates, a trihydrate and a monohydrate. The solubility of the trihydrate increases very rapidly with rise of temperature, and has been determined up to 26.1°. At temperatures above 24.7°, however, the trihydrate is metastable with respect to the monohydrate; for at this temperature the solubility curve of the latter hydrate cuts that of the former. ”

“ Hydration and dehydration.—Water sometimes unites directly with some of the constituents of a rock and produces hydrated minerals, i.e., minerals that have water as an element of their constitution, not simply water absorbed into their pores. A large class of minerals known as zeolites, because they swell up and undergo life-like contortions when their basic water is driven off by heat, are examples of hydrous products. ”

“ The urine is the main channel of excretion for the nitrogenous waste products. CO2, arising for the most part from the metabolism of carbohydrates and fats, is excreted mainly through the lungs. Water is excreted by the lungs, the kidneys and the skin.
So far no entirely satisfactory explanation has been given of how a fluid like urine, having an acid reaction and containing about one hundred times as much urea and generally more than twice as much sodium chloride as the blood, is formed in the kidneys. ”

“ The solution should be changed whenever it becomes cloudy. When fixation is complete the fixed and hardened tissue may be cut directly on the freezing-microtome or after-hardened and dehydrated in alcohol or acetone when it is to be imbedded. The dehydration in alcohol should be carried out in the dark and without previous washing of the tissue in the case of nervous tissue. ”

“ Evaporation of a solution at ordinary temperatures gives colourless monoclinic prisms of Th (SO4) 2·9H2O, which is isomorphous with uranium sulphate, U (SO4) 2·9H2O. Above 43° Th (SO4) 2·4H2O is deposited. B. Roozeboom (Zeit. phys. Chem., 1890, 5, p. 198) has described several other hydrates. ”

“ Physiologists declare that water is formed in the body by a direct union of oxygen and hydrogen, but those who have cultivated the drink-little habit need not hope to find an excuse for themselves in this fact: chronic ill-health betrays them. Water in organic relations with the body never exists uncombined with inorganic salts (especially sodium chloride) in any of the fluids, semi-solids, or solids of the body. It enters into the constitution of the tissues, not as pure water, but always in connection with inorganic salts. ”

“ Hydrogen and chlorine,” I muttered to myself. “The dumb-bell-shaped glass vessel which is fastened under the plank contains, without doubt, these two gases, and the tin canister which rests beneath them is full of nitro-glycerine.” Yes, I knew what this combination meant. When the first glint of the sun's rays struck upon the glass vessel it would be instantly shattered. The nitro-glycerine would explode by the concussion, and the balloon and I myself would be blown into impalpable dust beyond sight or sound of the earth. ”

“ The constituent parts of pure water, in volumes, are two parts of hydrogen and one of oxygen, and by weight one part hydrogen and eight parts oxygen. When pure it is transparent, tasteless, inodorous, and colorless, except when seen in considerable depths. But having such high solvent powers and affinity for almost every substance in nature, one can account for suspicions that science places on all waters, for it is never free from impurities. And well it may not, if doctors are to be believed, for they tell us, that chemically pure water is not best for man ”

“ In many cases the liquid is water, usually containing considerable quantities of saline matter dissolved in it. Sometimes the saline matters are present in such abundance that they cannot all pass into solution, but crystallise out, as in fig. 7—Nos. 3, 4, 5—where cubic crystals of the chlorides of sodium and potassium are seen floating in the liquid; in other cases the liquid is a hydrocarbon like the mineral oil which is present in great abundance in deep-seated rocks in many parts of the globe. ”

“ Perfectly pure water is without taste: even the pleasant character of freshly-drawn spring-water is due to the admixture of atmospheric air and carbonic acid. The manner in which water absorbs air is evidently due to a peculiar physical attractive force, the value of which we do not at present clearly perceive or correctly estimate. It is chemically composed of two volumes of hydrogen gas—the lightest body known, and at the same time a highly inflammable one—united with one volume of oxygen, which excites combustion, and continues that action,—producing heat and light,—with great energy. ”

“ The peculiar manner in which hydrogen gas appears to dissolve solid substances,—as iron, potassium, sodium, sulphur, phosphorus, selenium, and arsenic, may be explained by regarding the results as a manifestation of the powers of chemical affinity over the forms of bodies. In like manner, the solution of salt in water, or the mixture of alcohol in that fluid, may be viewed as chemical phenomena, although usually considered as simple cases of solution or mixture: alterations of temperature and other physical changes taking place in either. ”

“ By having a series of bottles of various sizes, filling them with the air to be tested, placing in each bottle a large tablespoonful of lime water, and then shaking them vigorously for 3 or 4 minutes, so that all the air in the bottle shall be brought in contact with the lime water, and all the carbonic acid be taken up by the lime, we shall find that in one bottle of the series the turbidity is just perceptible, while in bottles of less size the fluid remains clear, and in those of greater size it is dense. ”

“ Water recently boiled will absorb, if cold, about twice its bulk of chlorine gas, acquiring its color and characteristic properties. The moist gas, exposed to a cold of 32 deg., yields beautiful yellow crystals, which are a definite compound of one equivalent of chlorine and ten of water. If these crystals are hermetically sealed up in a glass tube, they will, on melting, exert such a pressure as to liquefy a portion of the gas, which is distinctly seen as a yellow fluid, not miscible with the water which is present. ”

“ Very dilute solution of chlorine, or of chloride of lime or soda, followed by a powerful emetic, or the stomach-pump. When the vapour has been respired, free exposure to fresh air, with the head a little elevated, and copious affusions of cold water, with moderate draughts of brandy-and-water, and the use of the smelling-bottle (ammoniacal) should be adopted. If need be, artificial respiration should be attempted, and the air around the patient should be slightly impregnated with the fumes of chlorine or chloride of lime. ”

“ Water is necessary, not only for digestion, nutrition, and all functional processes of life, but it is indispensable as a menstruum for medicinal substances. It is a necessary agent in depuration, or the process of purifying the animal economy, for it dissolves and holds in solution deleterious matter, which in this state may be expelled from the body. In fevers, water is necessary to quench the thirst, promote absorption, and incite the skin and kidneys to action. Its temperature may be varied according to requirements. Diluents are the vehicles for introducing medicine into the system. ”

“ Let us consider water then as acting as accessory to the air upon the skin, as removing from its surface substances which the first cannot dissolve, substances, which varying remarkably like those that compose the urine,287 have presented the transpiratory fluids to chemists, sometimes as alkaline, sometimes as acid, oftentimes as containing salts, sometimes charged with odoriferous substances, &c. Water is the general vehicle; when it is evaporated, it leaves the substances that are not volatilized like it. ”

“ Distilled water is the nearest approach to pure water obtainable, and it is said by physicians that such water is not desirable as a habitual and constant beverage. The human body requires certain mineral salts particularly for the bones and muscles, and while these salts are provided in a large measure by food, a number are also furnished [Pg 132] by drinking water. On the other hand, a wonderful natural process is accomplished by distilled or approximately pure water in that the water tends to dissolve, to add to itself, and to carry away whatever excess of solids may exist in the body. ”