Neutral salt

Neutral salt is a salt that does not react acidic or basic in aqueous solution, i. H. the pH of a previously neutral solution remains at a value of 7 after a neutral salt has dissolved. Another common definition, which basically corresponds to the above, understands neutral salts as salts that result from the complete neutralization of an acid with a base.

According to this differentiation, salts can be classified into three groups: 1. Neutral salts: By dissolving the salt in a solvent or a solution, the pH value of this solvent or this solution remains unchanged. 2. Acid salts: The pH value drops as a result. 3. Basic salts: The pH value increases as a result.

Examples

Sodium Chloride - NaCl
Ammonium acetate - CH ₃ COONH ₄

history

Due to the amphoteric character of the amino acids and proteins , they can react with acids , bases or salts . As early as 1879 Albrecht Kossel investigated the behavior of proteins towards neutral salts. The cation of the neutral salt binds to the negatively charged carboxylic acid group and the anion to the positively charged ammonium group. With albumins the solubility is increased ( salting in ), with globulins it is decreased ( salting out ). Paul Pfeiffer and co-workers used the amino acids as a simpler model system and found a variety of combinations with neutral salts. The solubility of the amino acids is always increased when they form molecular bonds with the neutral salt. These compounds can be isolated.

Others

The influence of neutral salts on the solubility of other compounds has been sufficiently investigated , especially for amino acids , and shows that the solubility changes drastically depending on the types of cations and anions. This effect is known as the Hofmeister effect and can be applied to many other biomolecule classes.

swell

AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .

Individual evidence

↑ A. Kossel: About the chemical composition of peptones . In: Journal of Physiological Chemistry . tape 3 , no. 1-2 , 1879, pp. 58-62 .
↑ Paul Pfeiffer , Fr. Wittka: About the salting out of amino acids and the separation of amino acids with the help of neutral salts . In: Reports of the German Chemical Society . tape 48 , no. 1 , 1915, p. 1041-1048 , doi : 10.1002 / cber.191504801146 .
↑ Paul Pfeiffer, J. Würgler: The Influence of the Solubility of Amino Acids by Neutral Salts . In: Hoppe-Seyler's journal for physiological chemistry . tape 97 , no. 2–3 , 1916, pp. 128-147 , doi : 10.1515 / bchm2.1916.97.2-3.128 .
↑ JP Greenstein, M. Winitz: Chemistry of the Amino Acids . Vol. 1, 1961, pp. 666-672.

[1] A. Kossel: About the chemical composition of peptones . In: Journal of Physiological Chemistry . tape 3 , no. 1-2 , 1879, pp. 58-62 .

[2] Paul Pfeiffer , Fr. Wittka: About the salting out of amino acids and the separation of amino acids with the help of neutral salts . In: Reports of the German Chemical Society . tape 48 , no. 1 , 1915, p. 1041-1048 , doi : 10.1002 / cber.191504801146 .

[3] Paul Pfeiffer, J. Würgler: The Influence of the Solubility of Amino Acids by Neutral Salts . In: Hoppe-Seyler's journal for physiological chemistry . tape 97 , no. 2–3 , 1916, pp. 128-147 , doi : 10.1515 / bchm2.1916.97.2-3.128 .

[4] JP Greenstein, M. Winitz: Chemistry of the Amino Acids . Vol. 1, 1961, pp. 666-672.