Salts

SALTS, products of the substitution of hydrogen ions in acids by metal ions; they can be obtained by various methods: 1) by substitution of the acid's hydrogen with a metal, e.g., Zn + H₂SO₄ = ZnSO₄ + H₂, or by displacing one metal in a salt with another: CuSO₄ + Fe = FeSO₄ + Cu; 2) by neutralization of acids with bases: NaOH + HNO₃ = NaNO₃ + H₂O; 3) by the action of an acid on a basic oxide: H₂SO₄ + CaO = CaSO₄ + H₂O; 4) by the action of an alkali on an acidic oxide: CO₂ + NaOH = NaHCO₃; 5) by the combination of an acidic oxide with a basic one: CO₂ + Na₂O = Na₂CO₃; 6) by the action of an acid on the salt of another acid; this method can be applied if the reaction products differ significantly in their solubility, e.g., a) when the acid of the decomposed salt is volatile or capable of forming volatile products: BaCO₃ + 2HNO₃ = Ba(NO₃)₂ + H₂CO₃ = Ba(NO₃)₂ + H₂O + CO₂ or b) when the acid of the decomposed salt is insoluble and precipitates: K₂SiO₃ + 2HCl = 2KCl + H₂SiO₃; 7) for obtaining salts, their interaction in solutions with the formation of insoluble compounds is significant: BaCl₂ + Na₂SO₄ = BaSO₄ + 2NaCl. From the reactions cited above, it is clear that a salt can also be viewed as a product of the substitution of hydroxyl ions of metal hydroxides by acid anions. In cases where all hydrogen ions of an acid are replaced by a metal or all hydroxyl ions of a base hydrate are replaced by acid anions, salts are called normal or neutral. If only a part of the hydrogen ions of a polybasic acid is replaced by a metal, the salt is called acid (NaH₂PO₄—monometallic acid sodium phosphate, NaHSO₄—acid sodium sulfate); if, in the hydrate of an oxide of a polyvalent base [Bi(OH)₃], only a part of the hydroxyl ions is replaced by acid anions, then the resulting salt is called basic: Bi(OH)₂NO₃—basic bismuth nitrate. Salts are solids; some of them are highly soluble in water. Salts of alkali metals and ammonium are almost all soluble in water. Salts of strong acids are also almost all soluble in water (with the exception of chloride, bromide, and iodide salts of silver, lead, copper, and mercury; sulfate salts of barium, strontium, radium, lead, and some other compounds). An important property of salts is the ability of their aqueous solutions to conduct electric current, which is due to the dissociation of molecules into ions. It is also characteristic of salts that their molecules possess pronounced polarity (see Dipoles). Besides simple salts, there are also complex ones (see Complex compounds). The nomenclature of salts is not sufficiently developed. The following names of salt anions are often used: Cl^-—chloride, OCl^-—hypochlorite, ClO₃^-—chlorate, ClO₄^-—perchlorate, Br^-—bromide, MnO₄^-—manganate, MnO₄^-—permanganate, S^2-—sulfide, SH^-—hydrosulfide, SO₃^2-—sulfite, HSO₃^-—bisulfite, SO₄^2-—sulfate, CrO₄^2-—chromate, Cr₂O₇^2-—dichromate, NO₂^-—nitrite, NO₃^-—nitrate, etc. The cation of a salt is given the usual name of the metal with an indication (in numerals) of the valence if the latter is variable, for example: iron(II) sulfate FeSO₄; copper(I) chloride CuCl; copper(II) chloride CuCl₂. The rational nomenclature of salts with complex ions is more complex and less developed. Salts are part of the tissues and fluids of the organism. Soluble salts determine the osmotic concentration and the concentration of hydrogen ions of physiological fluids, significantly influencing the degree of dispersion, aggregation, and swelling processes of tissue colloids. The correct ratio of the concentrations of individual ions in tissue fluids is of great importance for the organism; otherwise, the poisonous effect of individual ions appears; equilibrated or physiological solutions are those in which, while maintaining the osmotic concentration necessary for the organism, their poisonous effect is eliminated due to the antagonism of various ions. See also Ions, Mineral metabolism.