Law of Equivalent Proportions

from Wikipedia, the free encyclopedia

The law of equivalent proportions states that chemical elements always combine to form chemical compounds in the ratio of certain compound masses (" equivalent masses") or integer multiples of these masses . It was set up in 1791 by the German chemist Jeremias Benjamin Richter (1762-1807) without resorting to the atomic hypothesis . Richter is therefore considered to be the actual founder of stoichiometry . His law goes beyond the law of constant proportions drawn up soon after by Joseph-Louis Proust in 1797 and the law of multiple proportions , which was expanded by John Dalton in 1808 , but includes both. Dalton also demonstrably knew the fundamental work of Richter, but already based his explanation of the law on atomic theory.

Richter based his law on the practical experience that two salts, which react with one another, in turn form neutral compounds, and he wanted to quantify this phenomenon:

“Mathematics includes all those sciences in its field where there are only quantities, and a science consequently lies more or less in the circle of the art of measurement, the more or less quantities are to be determined. This truth led me, in chemical experiments, to the question whether and to what extent chemistry is a part of applied mathematics; it was especially agitated by the so common experience that two neutral salts, when they decompose one another, make neutral compounds again. The immediate conclusion, so I drew from this, could be no other than that there must be certain proportions between the constituents of the neutral salts. "

- JB Richter : Beginnings of stoichyometry or the art of measuring chemical elements, first part, 1792 (preface)

Richter first mixed the two salts calcium acetate and potassium tartrate in an aqueous solution . The solution remained neutral, which at the time did not seem obvious, and calcium tartrate precipitated . Richter generalized this fact and concluded that a salt mixture of A1B1 combined with A2B2 can form four mixed salts in certain mathematical combinations (A1B1, A1B2, A2B1, A2B2). From the ratios A1 / B1 = x, A2 / B1 = y etc., all individual salt mixtures can be calculated according to the neutrality of the resulting solution.

See also

Individual evidence

  1. ^ A b A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 23.
  2. ^ Wilhelm Ostwald : JB Richter, in Günther Bugge: The book of great chemists , Verlag Chemie, Weinheim 1974, Volume I, p. 375, ISBN 3-527-25021-2 .

literature

  • Jeremias Benjamin Richter: Beginnings of stoichyometry or the art of measuring chemical elements , first, second and third part, Breßlau and Hirschberg, 1792–93.
  • AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
  • C. Poggemann, The idealistic-romantic work "Beginnings of Stoichiometry" and its philosophical foundations in Christian-Platonic physics theology, in: Wilfried Schröder (ed.), Physics and Geophysics with Historical Case Studies (A Festschrift in honor of Karl-Heinz Wiederkehr) , Science Edition / Interd. Comm. History IAGA / History Commision DGG, 16th year 1997. Issue 2–5, ISSN  0179-5856 , pp. 326–345.
  • Günther Bugge: The book of great chemists , Verlag Chemie, Weinheim 1974, Volume I, p. 369, ISBN 3-527-25021-2 .