Dulong, Pierre-Louis à Ampère, André-Marie
Dulong, Pierre Louis à Ampère, André-Marie
5 août 1816 If I had delayed the reading of my paper for only one week, I would have lost the priority
for several rather important items. A paper has been received from Berzelius that deals with
the analysis of phosphates, of phosphoric acid, and phosphorous acid. We have agreed in very
few respects on the topics we both considered. He makes no mention of phosphatic acid nor of
hypophosphorous acid. Immediately following the reading of my paper, Gay-Lussac announced
verbally to the Académie that there are likewise four sulphur acids, namely, sulphuric
and sulphurous acid, which have been known for some time, and two new acids, which exist in the
sulfuretted sulfites (thiosulfates). However, up to now he has not been able to isolate these
acids. Your hypothesis as to the composition to the thiosulfates is applicable to the
hyposulfites, but in order for it to acquire any credence it will be necessary at least to
obtain by itself the phosphoretted hydrogen gas which is combined with phosphorous acid in
hypophosphorous acid. However, my analyses show that the phosphoretted hydrogen gas which is
produced under this condition ought to contain four times as much phosphorus as that which Davy
has analysed. I know perfectly well that the gas which bursts into flame spontaneously contains
more phosphorous than that Davy studied, but it is not at all probable that it contains four
times as much. Furthermore, I do not claim that this would be impossible, and when I had
determined the relation of this acid to the other compounds of phosphorous and oxygen I
immediately suspected that it was not a binary acid. I plan to clear up this doubtful point by
new experiments.
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Source de l'édition électronique de la lettre : 
Extrait de lettre publié en anglais.