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38 alchemy Rhazes, or Abû Bakr Mohammed ibn Zakaráyá el-Rázi, who lived circa 925, and Avicenna, or in Arabic Abû Ali el-Hosein ibn-Abdallah ibn-Sina, born 980, died 1037. The former, a Persian, practised medicine at Baghdad as a follower of Galen and Hippocrates. The latter, one of the most eminent of Moslem physicians and a voluminous writer, was a native of Bokhara. He is mainly known in the history of science by his Canon of Medicine, in which he describes the composition and preparation of remedies. He wrote at least one treatise on alchemy, but others attributed to him are probably apocryphal. Of his Philosophia Orientalis, mentioned by Roger Bacon and Averroes, no trace remains.

Although it is reasonably certain that the alchemists of the time of Geber and of his successors had a considerable acquaintance with manipulative chemistry, there were so many impudent literary forgeries during the alchemical period that the precise extent of the knowledge possessed by the early chemists must always remain uncertain.

A number of the ordinary chemical processes, such as distillation, sublimation, calcination, filtration, appear to have been known to, and to have been commonly practised by, the Arabian chemists; and many saline substances, such as carbonate of soda, pearlash, sal-ammoniac,