HYDROGEN

From Big Medical Encyclopedia

HYDROGEN (Hydrogenium, H) — chemical element VII of group of a periodic system of elements of D. I. Mendeleyev; at. number — 1, at. weight (weight) 1,00797. V.'s valency is equal in connections with nonmetals +1, with metals — 1. Three isotopes B. (tab.) are known.


It is applied in large numbers to synthesis of ammonia, to receiving margarine from vegetable oils, liquid fuel from black coal century; for filling of air devices (aerostats, radiosondes etc.), for autogenous welding and obtaining very low temperatures. Heavy isotopes B. are used during the studying of the mechanism chemical, biochemical, and fiziol, processes, and also in nuclear power.

Pure V. — the colourless, not having a smell and taste gas consisting of diatomic molecules — H2. It is the easiest of all known gases. Weight of 1 l of Century at t ° 0 ° and pressure of 760 mm is equal to 0,089870 g; density by air — 0,06952; molar volume at t ° 0 ° and pressure of 760 mm is equal to 22,428 l; critical temperature — 239,9 °; t ° KIP at 1 atm — 252,6 °; t ° pl — 259,1 °; liquid V.'s density — 0,0708 (at t ° — 252,8 °); firm V.'s density is 0,0807 (at t ° — 260 °). In 1 ml of water at t ° 0 ° and 18 ° respectively 0,0215 ml and 0,0185 ml of hydrogen are dissolved. It is well absorbed by nek-ry metals, especially palladium century; one volume of the last at t ° 0 ° and pressure of 760 mm absorbs apprx. 850 volumes of V., to-ry is completely allocated during the heating.

Crust contains apprx. 1% on weight, or 17,25 atomic percent of Century. Abundance of V. increases in the atmosphere with height: at sea level it makes apprx. 0,00005% on volume, upper layers (higher than 100 km) consist hl. obr. from Century. Free V. contains in the combustible gases which are emitted from the earth. It is formed during the rotting and fermentation of organic matters and therefore contains in intestinal gases of the person and animals. The ground mass of V. is in the connected state in the form of various connections. The most widespread of them is water, the cut is a part 11,19%

of V. Izvestno a large number of connections B. with carbon — hydrocarbons (see). Is petroleum composition, black coal, nek-ry minerals century; is a component of acids, the bases, acid and basic salts etc. Contains in a human body apprx. 10%

of V. V laboratories B. receive effect of acids on metals, napr, action by a chamois to - you on zinc: H 2 SO 4 + Zn = H 2 + ZnSO 4 .

In the equipment B. receive: 1) from the natural gas consisting generally of methane to-ry mix with water vapor and oxygen and heat to t ° 800 — 900 ° in the presence of the catalyst:

2CH 4 + O 2 + 2H 2 O = 2CO 2 + 6H 2  ; the received mix of gases is divided (usually at deep cooling);

2) at electrolysis of NaCl or KCl solutions as a by-product in production of alkalis, hypochlorites and chlorates.

Under the corresponding conditions of V. connects to the majority of elements of the main subgroups of a periodic system of elements. With oxygen forms water (H 2 O) and hydrogen peroxide (H 2 O 2 ). At V.'s combustion on air or in oxygen water is formed and heat is generated:

2H 2 + O 2 = 2H 2 O + 115,74 kcal.

V.'s ignition happens at t ° apprx. 580 °. Mix B. and oxygen in a volume ratio 2: 1 (detonating gas) it is explosive. Century directly connects to halogens, nitrogen, sulfur, carbon.

During the heating of alkali and alkaline earth metals (sodium, potassium, calcium, etc.) in V.'s stream the solid crystal matters called by hydrides a part turn out to-rykh negatively charged V. is:

2Na + H 2 = 2Na + H - .

Has strong recovery properties century and it is capable to connect to oxygen, even being a part of other connections, napr, oxides of heavy metals, or to join many organic compounds (see. Hydrogenation ). With the participation of atoms B. in organisms of animals and plants many proceed redoxreactions (see).

In comparison with atoms of all other elements atoms B. have the simplest structure. Atom of light isotope 1 H consists of one proton (atomic nucleus) and one electron rotating around it. Ionization energy of atom B., i.e. the energy necessary for a separation of an electron from the orbit, next to a kernel, makes 312 kcal / g-atom. Atomic nuclei of heavy isotopes have more complex structure: kernel of a deuterium ( 2 H) the kernel of hyzone consists of one proton and one neutron ( 3 H) — from one proton and two neutrons.

Detection and quantitative definition of gaseous V. in mix with other gases is made by cooling of gas mixture with a liquid air; at the same time all other gases, except helium and neon, are completely condensed. Chemically connected V.'s definition is made by its oxidation in water.


Bibliography: Remy G. Kurs of inorganic chemistry, the lane with it., t. 1, M., 1972; Melior J. W. Comprehensive treatise on inorganic and theoretical chemistry, v. 1, L., 1946.

V. P. Mishin.

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