It was mainly through the work of Nikolai Semenovich Kurnakov and his students that Berthollets opposition to Prousts law was shown to have merit for many solid compounds. Kurnakov divided non-stoichiometric compounds into berthollides  and daltonides depending on whether their properties showed monotonic behavior with respect to composition or not. The term berthollide was accepted by IUPAC in 1960. The names come from Claude Louis Berthollet and John Dalton, respectively, who in the 19th century advocated rival theories of the composition of substances.  Although Dalton "won" for the most part, it was later recognized that the law of definite proportions had important exceptions.