Experiments and observations on the specific gravities and attractive powers of various saline substances, pp. 7-41, extracted from: Philosophical Transactions of the Royal Society of London. Vol. LXXI. For the year 1781

KIRWAN, Richard

Edité par London: Lockyer Davis & Peter Elmsly, 1781

A propos de cet article

First edition. "His experiments on the specific gravities and attractive powers of various saline substances formed a substantial contribution to the methods of analytical chemistry, and in 1782 gained him the Copley medal from the Royal Society, of which he was elected a fellow in 1780" (Wikipedia). Affinity theories were used in one way or another by most chemists from around the middle of the 18th century into the 19th century to explain and organise the different combinations into which substances could enter and from which they could be retrieved. The goal of this paper "was to quantify the affinity between acids and bases. In 1720, Geoffroy had developed a chemical affinity table to visually represent the affinity of acids and alkalis in the production of salts. Intense study on affinity tables throughout the second half of the eighteenth century had culminated in 1775 with Torbern Bergman's monumental table with fifty rows and columns representing not only the alkalis and acids but also the salts they produced in order to examine double affinities. However, the size and complexity of Bergman's table showed that visual representation was becoming overly complicated. For every new acid or salt, a set of experiments, growing geometrically with each discovery, was needed to place it in the table. Kirwan's goal was to measure affinities numerically, rather than comparatively. Mirroring his work on the specific weight and heat of various airs, Kirwan now analyzed the affinities of substances for a common substance, marine air. This would also allow for easier study of double affinities by simply adding together and comparing affinity measurements through algebra. Kirwan's paper, 'Experiments and Observations on the Specific Gravities and Attractive Powers of Various Saline Substances,' laid out this experimental method for finding specific gravities and the results of experiments on several key chemical substances like spirit of salt and spirit of nitre. Kirwan, at times, draws from the chemical literature for his data rather than conducting new experiments. He quotes the work of Homberg, Lavoisier, and others. For each acid and alkali, Kirwan experimentally found how much marine acid air was needed to form a neutral salt. In finding the 'point of saturation' for acids and alkalis, Kirwan was drawing on the work of Homberg, whom he quoted. Unlike Homberg though, Kirwan studied the point of saturation in gases rather than aqueous solutions, giving him greater ability to isolate the substances involved. Kirwan suggested that there was a range of affinities dependent upon the respective quantities of the substances involved. When there were very different quantities of the substances, affinity would be high and the compound density would be low. When the substances were perfectly balanced, affinity would be low and the compound density would be at its maximum" (Stewart, Richard Kirwan's chemistry: heat, affinity, and phlogiston in the 1780s (2008), pp. 23-25). Richard Kirwan (1733-1812) was an Irish geologist and chemist. He was widely known in his day, corresponding and meeting with Lavoisier, Black, Priestley, and Cavendish. 4to, pp. 7-42 (slightly foxed).

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Détails bibliographiques

• Titre: Experiments and observations on the specific gravities and attractive powers of various saline substances, pp. 7-41, extracted from: Philosophical Transactions of the Royal Society of London. Vol. LXXI. For the year 1781
• Éditeur: London: Lockyer Davis & Peter Elmsly
• Date de parution: 1781
• Reliure: No Binding
• Édition: 1st Edition
• État de l'article: Very Good