D

D

dB

See: Decibel.

Decibel

Abbreviation: dB. Unit of measurement for the magnitude of sound pressure, sound intensity and acoustic power. For frequently measured sound pressure, this unit of measurement is equal to 20 times the logarithm of the quotient of the sound pressure and the reference sound pressure. It is called the sound pressure level. (A logarithmic scale is necessary because the sound pressure next to human ears may cover a range of several powers of ten.) Since the sound perception of the human ear not only depends on the magnitude of the sound pressure level but also on the frequency (number of oscillations per second), the sound level A - weighted according to the volume was introduced internationally as a measurement variable. The unit of measurement is the decibel A [dB (A)]. On the logarithmic scale, an increase of 10 dB (A) is roughly equivalent to a two-fold increase in volume. The previously used unit of measurement, DIN phon, is now obsolete. A change in volume of 1 decibel is perceptible to humans with good hearing (cf. Noise).

Decontamination

The elimination of toxic, microbial or radioactive contamination. Collective term for all treatment methods for isolating toxic products or rendering them innocuous.

Derivatives

Derivatives are chemical compounds derived from a parent substance by means of separation, addition or exchange of groups or atoms, and which still resemble the parent substance in terms of structure or properties.

Desorption

Reverse of adsorption. The release of gases, liquids or solids from surfaces.

Desulfurization

The removal of sulfur or sulfur compounds from fuels (gas, coal, crude oil) prior to combustion or the removal of sulfurous combustion products i.e. sulfur oxides from flue gases. In both cases, the objective is to lower sulfur dioxide emissions into the atmosphere. Desulfurization of gases and distillate heating oils and diesel fuels is possible and is already performed today. Desulfurization of residual heating oils or solid fuels is theoretically conceivable, e.g. by means of fuel gasification, but still requires a great deal of research. Several methods of desulfurizing waste gas at efficiencies in excess of 80% are available and in use.

Detergents

In Germany, this term was originally used for surface-active substances in general, which today are referred to as Tensides. In other countries, the word detergents was always understood to mean finished washing agents, a meaning which has also become widespread in Germany.

Deutsches Institut for Normung e.V. (German Standards Institution)

See: DIN.

De-dusting system

Technical systems such as fabric filters, electrostatic filters, wet filters and other Separator for reducing emissions.

Dialysis

The separation of dissolved particles according to their particle size as a result of Diffusion through semipermeable membranes. Gentle means of purification of macromolecules (e.g. proteins) in chemistry and technology.

Diffusion

The distribution of molecules of one substance into another, resulting from thermal motion, dependent on concentration gradient, temperature and molecular weight. The diffusion constant indicates the rate at which a diffusing quantity of substance spreads through a unit area per unit of time.

Dilute acid

Diluted (20%) used sulfuric acid. Accrued in large quantities in the chemical industry, e.g. in the preparation of titanium dioxide. Dilute acid is regenerated.

DIN

Abbreviation for the German Standards Institution, which publishes standards in the form of standards sheets with the designation DIN. All DIN standards together make up the German Collection of Standards. This includes around 20,000 DIN standards, i.e. definitions, dimensions, testing procedures, variable determinations etc. for technical areas, sciences, medicine, agriculture and numerous other areas of human activity. Accounting for approximately 2/ 3 of all standards, the field of engineering and technology is by far the largest.

Dioxins

Synonym for chlorinated dibenzo-p-dioxins. Highly toxic compound of chlorine and hydrocarbon causing serious health damage and developmental disorders.

Dirt

Substances that undesirably stick to other materials or are distributed throughout other materials. Subjective perception determines whether or not this is dirt. See: Impurities.

Disperse system

Chemistry: System of two or more phases, in which one phase (the dispersed substance or dispersed phase) is finely distributed in another (disperser or dispersing medium). Depending on the degree of dispersion (degree of distribution) of the disperse phase, a distinction is made between:

- coarsely dispersed: particle size larger than 100 millimeters and
- molecularly disperse: particle size less than 1 millimeter.

Disposable packaging

Packaging disposed of after use (throw-away packaging). Packaging of this type has been the subject of controversy in recent years in connection with waste disposal. The fact was occasionally overlooked that numerous packaging materials are by their very nature disposable (cans, plastic packaging for frozen foods, tubes), without which the transport and distribution of many foods would not be possible. Disposable packaging means a reduction in cleaning processes, which are cost-intensive and harmful to the environment. Ecobalances are used to compare and evaluate disposable and returnable packaging for each product to determine the most favorable packaging, taking into account both ecological and economical aspects.

Dissociation

Chemistry: The process by which a homogeneous substance is broken down into its constituents or into certain groups of atoms. Caused by the weakening of the binding forces when thermal energy is introduced (thermal dissociation) or when transferred to solvents which lower the attractive force of particles, dissolved in the form of ions (electrolytic dissociation), as a result of a high dielectric constant (e.g. water).

Dumping ground

Controlled, environmentally compatible and supervised dumping of waste, as opposed to disorderly, unsupervised dumping. Controlled dumps are equipped with base sealing to prevent toxins from contaminating groundwater.

Dust