Precursors, chemical reactants, reagents, analytical reactants

The State license for the activity connected with turn of precursors is required

Chemical reactants (reagents chemical) — the chemical preparations intended for chemical analysis of research, different laboratory works. In most cases chemical reactants represent individual substances; however carry to reactants also some mixes of substances (for example, petroleum ether). Sometimes reactants are called solutions of quite difficult structure of special purpose (for example, Nessler's reagent — for ammonia definition).

On degree of purity and appointment distinguish and respectively mark chemical reactants: special purity (o. s. ch. ), chemically pure (h. ch. ), pure for the analysis (ch. d. ), pure (h), cleared (ochishch. ), the technical products packaged in small container (tekhn. ).

Application

Many chemical reactants are specially made for laboratory use, but the purified chemicals which are let out for the industrial purposes find application also.

Types of reactants

Chemical reactants divide also into groups depending on their structure: the inorganic, organic reactants, reactants containing radioisotopes, etc. To destination allocate first of all analytical reactants, and also chemical indicators, organic solvents.

Analytical reactants

The value and practical value of analytical reactants are defined mainly by their sensitivity and selectivity. Sensitivity of chemical reactants is the smallest quantity or the smallest concentration of substance (ion) which can be found or quantitatively defined at addition of reactant. For example, the magnesium ion at concentration of 1,2 mg/l gives still noticeable deposit after addition of solutions of disodium hydrogen phosphate and ammonium chloride. There are much more sensitive reactants. Such reagents which give characteristic reaction with the analyzed substance or ion in the known conditions, irrespective of presence of other ions are considered specific. Specific reagents is known very little. In analytical chemistry it is necessary to deal mainly with the selection and group reagents. The selection reagent interacts with small number of ions. Group reagent is applied to simultaneous allocation of many ions. The selection analytical reagents represent mainly complex organic compounds capable to formation of characteristic inner - complex compounds with ions of metals. Many reagents for the organic functional analysis are known. For example, phenylhydrazine, 2,4 dinitrophenylhydrazine, semicarbazide and thiosemicarbazide are applied to qualitative and quantitative test of aldehydes and ketones.

Accident prevention

Many chemical reactants are poisonous, flammable, explosive; therefore during the work with them it is necessary to observe the corresponding and enclosed precautionary measures.