In 1765 the business was sold, and Scheele obtained a situation in Malmö with an apothecary named Kjellström. His master testified that he had extraordinary application and ability, and related that he was in the habit of criticising all that he read, saying of one statement, “This may be the case”; of another, “This is wrong”; of a third, “I shall look into this.” His memory was prodigious: he is said never to have forgotten anything which he had read relating to his favourite subject. He took little interest in anything else, and both his employers appear to have encouraged him to the utmost in his favourite pursuit. In 1768 he left Malmö for Stockholm; but here the exigencies of his duties interfered with his leisure for experimentation. While there, in conjunction with his friend Retzius, he discovered tartaric acid, which up till then had never been separated from tartar, its potassium salt. Here too he made investigations on the acid of fluor-spar (hydrofluoric acid); but finding his time too greatly occupied with routine work, he took a situation at Upsala, the seat of the largest university of Sweden, in 1770. At that time Bergman was Professor of Chemistry there, and Linnaeus occupied the Chair of Botany; both had then achieved a wide reputation. With Bergman he soon established close relations, and Retzius wrote that it was difficult to say which was pupil and which teacher. While at Upsala he wrote his great work on _Fire and Air_, which we shall shortly have to consider. From his laboratory notes it appears that before 1773 he had obtained oxygen by the ignition of silver carbonate, red mercuric oxide, nitre, magnesium nitrate, and from a mixture of arsenic acid and manganese dioxide. Here too he discovered chlorine, and made researches on manganese, arsenic, and baryta. In 1775 he was elected a member of the Royal Swedish Academy of Sciences, an honour which much improved his social status. In the same year he became manager of a business at Köping, where he passed the rest of his days, in spite of urgent appeals to engage in more remunerative work; indeed, he was strongly pressed to go to Berlin, and also, it is said, to London, for his publications had led to his recognition as one of the greatest chemists of the age. His book on _Fire and Air_ was not published for some years after the manuscript had been in the printer’s hands. We learn from his letters that he was much afraid of being anticipated in his discoveries, as indeed events showed that he had reason to be.