H

H

Halogenated hydrocarbons

Abbreviation: HH. Aliphatic or aromatic hydrocarbons in which hydrogen is partially or completely replaced by one or more halogens (e.g. carbon tetrachloride).

Halogens

These so-called "salt formers" are a group of non-metallic elements such as fluorine, chlorine, bromine and iodine. They form salts with typical metals to produce fluorides, chlorides, bromides and iodides, Sodium chloride. The abbreviation for halogens is X, e.g. in AOX (absorbable organic halogen).

Hard

Water hardness. Property of water determined by its content of calcium salts and magnesium salts (usually hydrogen carbonates). One German degree of hardness (1° dH) is equal to 10 milligrams of calcium oxide or 7.19 milligrams of magnesium oxide in one liter of water. Soap does not foam well in hard water because it forms insoluble calcium and magnesium salts. Warm water systems and heating units require soft water because otherwise scale (calcium carbonate) is deposited. In technical equipment, water softening is carried out via:

1. distillation
2. precipitation with soda or sodium phosphate
3. in the exchange process via so-called water softening systems
4. in the household via softening agents inherent in washing powders and cleaning agents

Hazardous incident provision

Set of rules pertaining to plant safety in plants containing certain hazardous substances or in which an operational failure could occur. This provision is the 12th provision of the Federal Pollutant Control Act and requires operators of plants that require authorization to set up and operate the plant in such a way as not to place in danger the neighborhood or the general public. This requirement applies to both existing plants and new plants. In addition to protective measures for the general public and the neighborhood (See: Immission control), the failure provision also includes work protection measures, because according to the legislative body, it is primarily the plant workers who are endangered in the case of plant failure.

Hazardous substance regulations

Regulations pertaining to hazardous substances: German Federal regulations based on the German Chemicals Act (See: Chemicals Act); replaces the Working materials ordinance and the poison prescriptions. Stipulates extensive measures for the placing on the market and handling of hazardous substances, especially regarding classification, labeling and packaging of dangerous substances and preparations, threshold values for carcinogenic substances, notification and permission regulations, instructing employees, medical screening, determination of hazardous substances by employers, protective measures.

Heavy metals

Metals with a density of over 4.5. Among the heavy metals are non-ferrous, ferrous and precious metals.

Heavy-metal compounds

Chemical compounds that contain heavy metals. Many heavy-metal compounds have a poisonous effect on the human organism, e.g. lead, cadmium, mercury, thallium and uranium salts. Some heavy metals (e.g. iron), in the form of biologically active complexes, serve as enzymes for metabolic processes important to life.

Heterogeneous

Term used for different, completely differing, varying.

HH

See: Halogenated hydrocarbons.

Hydrocarbons

HC: CXHy, organic compounds consisting of carbon and hydrogen. These make up the primary elements of all organic compounds. The lower components are odorless combustible gases, the middle components are usually gasoline and petroleum-like liquids and the upper components are solid substances. Distinctions are made between aliphatic, alicyclic and aromatic compounds. Some hydrocarbons are technically very important, e.g. as fuels (natural gas, propane, gasoline, benzene, etc.).

Hydrogen ion concentration

See: pH value.

Hydrogen ions

Positively charged protons; they attach to the negatively charged ends of water molecules to form H3O+ (hydronium ions), which are present in all acids and acidic salts.

Hydrolysis

Splitting caused by water. Modification of chemical compounds:

Hydrophilic

Designation used to describe something that likes water or is water-friendly.

Hydrophobic

Designation used to describe something that is water-repellent, technically waterproof.

Hygiene

Health care and practice. Doctrine of maintaining health of both the individual and the general public, prevention of illnesses and harm to health as well as positive promotion of health. M. von Pettenkofer (1818 to 1901) scientifically justified hygiene. A distinction is made between private and public hygiene. The latter has extended to become the public health system. The three work areas of hygiene are:

1. See: Environmental hygiene
2. social hygiene
3. psychological hygiene

Hygrometer

Instrument used to measure humidity. The hair hydrometer measures the relative humidity via the lengthening of a degreased human hair, the psychrometer (aspiration psychrometer) measures the absolute humidity via the cooling of a wet thermometer in the air current, the dew-point hydrometer indicates the dew point by condensation formation on a metal vessel that has been cooled by ether evaporation.

Hygroscopic

Said of materials that readily attract and absorb moisture from the air.