Lot 279: WAALS, Johannes Diderik van der (1837-1923). Autograph letter signed ("JD van der Waals") to Henri Becquerel (1852-1908). Amsterdam 22 June 1898. 3 pages, in French, 8 o, single folded sheet, with envelope. English translation included.

A highly technical scientific letter, full of scientific formulae, directly concerning Waals field of research, written to Becquerel, who received the Nobel Prize in physics in 1903. The letter criticizes a formula on the mixtures of a gas authored by Daniel Berthelot and introduced to the Academy des Sciences by Becquerel in 1898. "I have always believed that as far as the value of a12 is concerned, nothing can be concluded a priori. From the principle of symmetry it follows only that the second term of A has to contain the coefficients p and q in the same manner-but, as for the value of a12 it could be something completely different than Va1a2. The molecular attraction does not depend simply on the molecular weight, but possesses something specific for which we have not yet discovered the cause but which, however, exists." A letter with highly desirable content linking two physicists of the first rank. Van der Waals letters are very scarce on the market.