Unpublished paper and letters, 'Observation sur la manière de former l'alun par la combinaison directe de ses principes contituants' ['Observation on the way of forming alum through the direct combination of its constituent parts'] by [Jean Antoine Claude] Chaptal Chaptal's paper discusses ways in which alum is formed, including by combining clay and vitriolic acid [sulphuric acid], or through the decomposition of pyrite schist. Preceded by two covering letters in English from R J [Richard Joseph] Sullivan to Sir Joseph Banks. Subject: Chemistry Whilst the Royal Society declined to publish this essay, it was published in the Mémoires de l’Académie royale des sciences in 1788: Chaptal, Jean Antoine Claude. 'Observation sur la manière de former l'alun par la combinaison directe de ses principes contituans'. Mémoires de l’Académie royale des sciences, tome 10, 1788, pp 768-777. [1789]