16G Biographical Account of [Sept. 



5. His next dissertation, published likewise in 1775, contains 

 the discovery of arsenic acid, and an account of its properties. He 

 had shown in his dissertation on manganese that phlogiston was one 

 of the constituents of white oxide of arsenic ; the object of the 

 present researches was to discover the other constituent of that 

 substance. This he conceived to be arsenic acid. So complete is 

 this dissertation, that but little has been since added to our know- 

 ledge of arsenic acid ; except accurate information respecting its 

 composition, and some improvement in the method of obtaining it. 



6. It seems to have been about this time that Scheele discovered 

 oxalic acid by heating a solution of sugar in nitric acid. Bergman's 

 dissertation on it made its appearance in 1776, as an inaugural 

 dissertation ; and as no notice was taken in it of Scheele, Bergman 

 passed for some time as the real discoverer. But the truth was 

 gradually divulged, and has been long universally known. Indeed, 

 1 put the question to Assessor Gahn, who was at that time a student 

 at Upsala, and in terms of friendship both with Bergman and 

 Scheele ; and he assured me that Scheele was the person who dis- 

 covered oxalic acid. 1 regret that I did not ask for some information 

 respecting the history of the discovery. But my stay at Fahlun was 

 so short, and I had so much to a>k from a man of Gahn's general 

 iaformation of the interesting persons with whom he had been in 

 habits of intimacy, that many material points escaped my recollec- 

 tion at the time. 



7- Scheele's first dissertation after his removal to Hoping was 

 upon the Nature of Silica and Alumina, both of which he showed, 

 contrary to the opinion of Beaume, to be peculiar earths, not 

 capable of being transmuted into each other, or into any other 

 known earths. 



8. His next dissertation was published in 177^> in ^ e Memoirs 

 of the Stockholm Academy, as indeed was the case with all the 

 preceding. It was the analysis of a urinary calculus, which he 

 showed to consist of a peculiar acid, the properties of which he 

 described with his usual minute accuracy. This is the acid now 

 well known by the name of uric acid. This paper was the com- 

 mencement of our knowledge of urinary calculi, which has been 

 since carried to so great a height by succeeding chemists. 



This dissertation contains likewise some very important remarks 

 on the constituents of urine, and may be considered as the first 

 approach to an analysis of that very complicated liquid. 



9. Scheele's next publication was his work on Air and Fire, 

 which was fir>t printed in 1777? though from the prodigious number 

 of experiments which it Contains it must have cost him many years 

 of labour. In every point of view it must be considered as one of 

 the most extraordinary works that ever appeared ; and contains a 

 vast number of curious discoveries, some of which had been anti- 

 cipated by Dr. Priestley ; but the greater number were new, even 

 when the work On Air and Fiie appeared. The object of the work 

 was to show that heat is a compound of oxygen and phlogiston, 



