CHEMISTRY GLOSSARY

hexagonal crystal system    →   heksagonski kristalni sustav

Hexagonal crystal system is based on four crystallographic axes. The system of crystallographic axes of the hexagonal crystal system consists of three equivalent horizontal (equatorial) axes of which the positive ends make an angle of 120°. These axes are sometimes denoted as a, b and d axes. The fourth axis is (c) is perpendicular to and shorter or longer than the other three.

high fructose corn syrup    →   visoko fruktozni kukuruzni sirup

High fructose corn syrup (HFCS) is commonly used in place of sugar in foods and drinks. Corn starch is hydrolyzed to glucose, which is then treated with glucose isomerase to produce a fructose-rich mixture. HFCS is available in a number of forms, named according to the percentage of fructose they contain, HFCS-55 for instance contains 55 % fructose and 45 % glucose. The enhanced sweetness, low cost and ease of use are the main reasons why manufacturers now prefer to use high fructose corn syrup instead of sugar.

Hirsch funnel    →   Hirschov lijevak

Hirsch funnels are essentially smaller Büchner funnels and primarily used to collect a desired solid from a relatively small volume of liquid (1-10 mL). The main difference is that the plate is much smaller, while the walls of the funnel angle outward instead of being vertical. It is named after the German chemist Robert Hirsch (1856-1913).

histidine    →   histidin

Histidine is an electrically charged amino acids with basic side chains. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested. Histidine is perhaps the most common and versatile catalytic residue in proteins. The imidazole sidechain of histidine has a pKa of approximately 6.0. This means that, at physiologically relevant pH values, relatively small shifts in pH will change its average charge. The unprotonated imidazole is nucleophilic and can serve as a general base, while the protonated form can serve as a general acid. In addition, it is often a ligand for transition metal ions such as iron and zinc.

• Abbreviations: His, H
• IUPAC name: 2-amino-3-(1H-imidazol-5-yl)propanoic acid
• Molecular formula: C₆H₉N₃O₂
• Molecular weight: 155.15 g/mol

pK    →   pK

pK is the negative logarithm (base 10) of an equilibrium constant K.

Planck constant    →   Planckova konstanta

Planck constant (h) is a constant that, when multipled by the frequency of radiation gives the quantity of energy contained in one quantum.

Equal to 6.626 075 5(40)·10^-34 J s. It was named after Max Planck (1858-1947).

homologous series    →   homologni niz

Series of compounds which have a common general formula and in which each member differs from the next member by a constant unit, which is the methylene group (-CH₂-) is called the homologous series. Members of a homologous series are called homolog.

An example of the homologous series with some of their homologs are given below. Straight chain alkanes having general formula C_nH_2n+2

Hooke’s law    →   Hookeov zakon

Hooke’s law stating that the deformation of a body is proportional to the magnitude of the deforming force, provided that the body’s elastic limit (see elasticity) is not exceeded. If the elastic limit is not reached, the body will return to its original size once the force is removed. The law was discovered by English physicist Robert Hooke in 1676.

If a body on elastic spring is displaced from its equilibrium position (i.e. if the spring is stretched or compressed), a restitution force tries to return the body back in its equilibrium position. The magnitude of that force is proportional to the displacement of the body

Where F is the restitutional (elastic) force, x is the displacement of the body and k is the spring constant, which depends on dimensions, shape and material of the spring.

hybrid orbital    →   hibridne orbitale

Hybrid orbital is an orbital created by mixing together atomic orbitals to form an equal number of new hybrid atomic orbitals. For example, a common hybridization is sp³ where s orbital combine with a three p orbitals to form four new orbitals. After hybridization, all hybrid orbitals have the same energy, lower than p orbitals, but higher than s orbitals.

plastic sulphur    →   plastični sumpor

Plastic sulphur is the shape of sulphur which emerges when hot, liquid sulphur pours out in the water. It can be stretched in long fibres is unstable unstable. It easily solidifies.