DALTON, John. New Theory of the Constitution of mixed Aeriform Fluids, and particularly of the Atmosphere
London: For William Nicholson, 1801. First edition.

The first appearance of Dalton’s law of partial pressures. In this four-page letter written to William Nicholson (dated Sept. 14, 1801 and published in the October 1801 issue of Nicholson's jounral) Dalton gave the the first enunciation of his famous law of partial pressures:

When two elestic fluids, dented by A and B, are mixed together there is no mutual repulsion amongst their particles; that is, the particles of A do not repel those of B, as they do one another. Consequently, the pressure or whole weight upon anu one particle arises solely from those of its own kind.

"Although we now know that Dalton was inaccurate when he said that only like atoms in a mixture of gases repel and unlike atoms are indifferent toward each other, Daltonøs basic ideas did point him in the correct direction, causing him and his followers to reject a commonly held theory that all atoms in matter were alike. Dalton believed that atoms of different elements had different sizes and masses and that each element had its own unique and identical kind of atoms - all key points of his atomic theory." (Pickover: Archimedes to Hawking, p.179).

4to: 267 x 215 mm. In: Journal of Natural Philosophy, Chemistry, and the Arts, Vol. 5 (for the year 1801, printed 1802), pp. 241-244. (4, VIII, 352, 10 pp. and 18 plates. Contemporary speckled calf, finely re-backed.