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20/20

Subject: Music

This US group was formed in Los Angeles, California, in 1978 by Steve Allen (guitar, vocals) and Ron Flynt (bass, vocals), two expatriate musicians from Tulsa, Oklahoma. Drummer Mike Gallo ...

benzopyrene

benzopyrene   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
22 words
Illustration(s):
1

...A crystalline aromatic hydrocarbon, C 20 H 12 ; m.p. 179°C. It is found in coal tar and is highly carcinogenic....

HNIW

HNIW   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
42 words
Illustration(s):
1

... ( hexanitrohexaazaisowurtzitane ) A powerful explosive, C 6 N 12 O 12 . It has a three-dimensional bridged structure containing six N-NO 2 groups. Also known as CL20 , it is extremely sensitive and so far has not been produced in bulk....

superphosphate

superphosphate   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
103 words
Illustration(s):
2

...A commercial phosphate mixture consisting mainly of monocalcium phosphate. Single-superphosphate is made by treating phosphate rock with sulphuric acid; the product contains 16–20% ‘available’ P 2 O 5 : Ca 10 ( PO 4 ) 6 F 2 + 7H 2 SO 4 = 3Ca ( H 2 PO 4 ) 2 + 7CaSO 4 + 2HF Triple-superphosphate is made by using phosphoric(V) acid in place of sulphuric acid; the product contains 45–50% ‘available’ P 2 O 5 : Ca 10 ( PO 4 ) 6 F 2 + 14H 3 PO 4 = 10Ca ( H 2 PO 4 ) 2 +...

hydrogen peroxide

hydrogen peroxide   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
216 words
Illustration(s):
1

...with an anthraquinone) of hydrogen and water in the presence of oxygen. Hydrogen peroxide readily decomposes in light or in the presence of metal ions to give water and oxygen. It is usually supplied in solutions designated by volume strength. For example, 20-volume hydrogen peroxide would yield 20 volumes of oxygen per volume of solution. Although the peroxides are formally salts of H 2 O 2 , the compound is essentially neutral. Thus, the acidity constant of the ionization H 2 O 2 + H 2 O ⇌ H 3 O + + HO 2 − is 1.5 × 10 −12 mol dm −3 . It is a strong...

amino acid

amino acid   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
199 words
Illustration(s):
1

...hydrogen or an organic group and determines the properties of any particular amino acid. Through the formation of peptide bonds, amino acids join together to form short chains ( peptides ) or much longer chains ( polypeptides ). Proteins are composed of various proportions of about 20 commonly occurring amino acids (see table). The sequence of these amino acids in the protein polypeptides determines the shape, properties, and hence biological role of the protein. Some amino acids that never occur in proteins are nevertheless important, e.g. ornithine and...

halogens

halogens   Quick reference

A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
443 words
Illustration(s):
1

...form covalent compounds, with single bonds. All are reactive elements with the reactivity decreasing down the group. The electron affinity decreases down the group and other properties also show a change from fluorine to astatine. Thus, the melting and boiling points increase; at 20°C, fluorine and chlorine are gases, bromine a liquid, and iodine and astatine are solids. All exist as diatomic molecules. The name ‘halogen’ comes from the Greek ‘salt-producer’, and the elements react with metals to form ionic halide salts. They also combine with nonmetals, the...

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