Hydrocarbon Furnace
A furnace having special burners suitable for using liquid fuel. The burners consist of an apparatus which allows a forced jet of air and steam to carry with them a certain quantity of petroleum which is distributed into the furnace in the form of spray, and there burns with an intensity proportionate to the amount of fuel supplied. Hydrogen is the lightest substance known, and possesses nearly all the properties of a non-metal in such perfection, that chemists have long hesitated to class it with the metals, though its chemical relations clearly show it to belong to that class of elements. It combines with nearly every non-metal, but with only two or three of the metals. Hydrogen is colorless, tasteless, and inodorous when quite pure. It is inflammable, and burns with a pale yellowish flame, evolving much heat but very little light. The result of the combustion is water. It has never been liquefied, and is even less soluble in water than oxygen. It is incapable of sustaining life, but contains no poisonous properties. Hydrogen is never found free in nature, but exists abundantly in combination, forming one ninth by weight of water, and a considerable proportion of all organized substances. It is the lightest of all known substances, being 16 times lighter than oxygen and 14 1/2 times lighter than air; its density is placed at 0.0692 referred to that of air as unity, 100 cubic inches weighing about 2.14 grains.
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Hydrocephalus
a form of dropsy in the ventricles of the brain, or in the arachnoid cavity, in children, and usually rapidly fatal, though cases have been known to go on to adult life.
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Hydrochloric Acid
(HCl), a gaseous compound of equal volumes of hydrogen and chlorine. It is evolved during volcanic eruptions, and is found in the water which collects in the crevices of mountains, as well as in rivers which take their rise in volcanic formations, especially in South America. It may be produced by decomposing common salt with sulphuric acid (2Na Cl+ H2SO4 =2HCl + Na2SO4), or by bringing equal volumes of chlorine and hydrogen together and exposing the mixture to diffused daylight with condensation, as it explodes in direct sunlight.
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Hydrocyanic Acid
cyanide of hydrogen, hydric cyanide, hydrogen cyanide, prussic acid. Discovered by Scheele in 1782.
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Hydrodynamics
a department of science which treats of the nature of liquids in motion, as opposed to hydrostatics, which investigates the condition ondition of their equilibrium when at rest.
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Hydrofluoric Acid
hydrogen fluoride, fluoride of hydrogen, hydric fluoride, HF. The anhydrous acid is obtained by neutralizing in a platinum dish the aqueous solution of hydrofluoric acid with caustic potash, and evaporating the solution.
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Hydrogen Dioxide
hydrogen peroxide, H₂O2, or HO - OH. Obtained by the action of dilute sulphuric acid and barium peroxide, BaO2.
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Hydrogen Peroxide
a compound of hydrogen and oxygen, containing a larger proportion of oxygen than water, ater, the other compound of these elements.
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Hydrogen Sulphide
H2S, sulphide of hydrogen, hydric sulphide, sulphydric acid, hydrosulphuric acid, sulphuretted hydrogen. A gas obtained by passing hydrogen through sulphur, or by burning sulphur vapor in hydrogen.
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Hydrography
a branch of science which deals with the measurement and description of the seas, lakes, rivers, and other waters, as used for purposes of commerce or navigation; the art of marine surveying and of the construction of charts.
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Hydroida
in ZOology, a typical sub-class of Hydrozoa. They have an alimentary region or polypite provided with an adherent disk or hydrorhiza and prehensile tentacles. Unlike hydra, the type of the sub-class, most of the hydroida live in societies, each of which constitutes a polypidom so like a seaweed that it is often collected as such. But while the apertures on an ordinary seaweed are only minute pores, the Hydroida have little cup-like cells along the stem and at the extremities of the branches, in which the individual polyp lives. The cells have a small hole at the bottom, and the stock is hollow, so as to enable the individual polyps to remain part of a compound organism. The sub-class is divided into five orders, Hydrida, Corynida, Sertularida, Campanularida, and Thecomeduse. The Polyzoa or Bryozoa, once ranked with the sub-class, now figure as a distinct class, arranged under the subkingdom Molluscoida. See HYDROZOON.
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Hydrokinetics
that branch of hydrodynamics which treats of the application of forces producing motion in fluids, having thus to do with the flow of liquids in pipes, its issue from orifices under certain pressures, etc.
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Hydromechanics
a term sometimes used to include hydrodynamics and hydrostatics, as also hydraulics, or the department of engineering which deals with the application of liquids in motion to machinery. Hydromechanics is sometimes limited to the latter department alone. On the other hand, hydraulics is sometimes made to cover hydrodynamics.
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Hydrometer
an instrument for determining the relative densities of liquids. Distilled water is usually referred to as the standard of comparison. It consists essentially of a bulb or float weighted at bottom so as to float upright, and having an elongated stem, graduated to indicate the density of the liquid by the depth to which it sinks.
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Hydroscope
an instrument for measuring the dampness or moisture of the air or of any other gas.
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Hydrostatic Press
a machine in which the pressure applied to a small piston is by means of water transmitted to a larger one; great pressure is thus produced, the increase being in the proportion of the excess of the sectional area of the one piston over the other. In application the different parts of a hydrostatic press occupy every possible position with regard to each other, and in many the force pump is worked by hand. Great force, with slow motion, is communicated to a piston by means of water forced into the large cylinder in which it moves, by a forcing pump of small diameter, to which the power is applied, the principle involved being the same as in the hydrostatic bellows.
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Hydrostatics
a department of science which treats of the conditions of equilibrium in liquids. For a liquid to remain at rest in any vessel, first, its surface must be everywhere at right angles to the forces which act on the molecules of the liquid, and, second, every molecule of the mass of the liquid must be subject in every direction to equal and contrary pressure. If the same liquid be placed in several vessels freely communicating with each other, it will stand in them all at the same horizontal level. If two or more liquids be placed in the same vessel they will arrange themselves according to their relative densities, after which the equilibrium will be stable. According to Hallam, the real creators of the science were Castellio (1577-1644), and Torricelli (1608-1647).
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