AS Biographical Account of [Junz, 
a passion for chemistry, which he cultivated himself even at that 
time with success. Ina short time they were united together by 
the bonds of intimate friendship. 
M. Descotils began his scientific career at the commencement of 
the troubles of the revolution; and towards the end of 1792 he was 
obliged to embark in quality of novice in a small vessel belonging to 
the state, from which he passed into a vessel stationed in the roads 
of Cherbourg. Soon after, by the advice of Dr. de Laville, for 
whom he always expressed a particular esteem, he resolved to stand 
candidate for the place of Eleve in the School of Mines, which 
Government had Just re-established. He received information of 
his admission into that school at the same time with the news of his 
nomination to the situation of aspirant in the marine; but he did 
not hesitate in his choice. Renouncing the dangers of the sea, and 
preferring study, and the pleasures of a life of tranquillity, he re- 
turned to Paris, where he gave himself up entirely to his taste for 
chemistry. 
In the year 1798 a great expedition was talked of, the object of 
which was unknown. MM. Berthollet and Monge, who were to 
' form a part of it, proposed to Descotils to accompany them. ‘The 
proposal was accepted; and Descotils, ignorant of his destination, 
but sure of acquiring information from these philosophers, so de- 
servedly celebrated, gave himself up to his destiny ; and, after.a 
voyage of 40 days, found himself on the coast of Egypt. 
During his abode in that burning climate, and in the midst of 
dangers constantly returning upon him, he gave himself up to 
several scientific researches, and he was one of those philosophers 
of whom the Institute of Egypt had to boast. On his return to 
Paris he got the management of the Laboratory of the School of 
Mines ; and in 1809 he was raised to the rank of Engineer in Chief, 
which he so well deserved. 
Notwithstanding the duties which Descotils had to discharge, his 
short career was marked by numerous experimental labours. We 
are indebted to him for many analyses of minerals,* in which he 
has shown a great deal of skill; but we shall merely mention such 
of his researches as have given him a distinguished place among 
chemists. 
His most important memoir is relative to the cause of the colours 
which certain salts of platinum assume (Ann. de Chim. xlviii. 153). 
He has shown that these colours are owing to the presence of a 
particular metal, which has been since distinguished by the name of 
iridium, and which is found likewise in the residaum which pla- 
tinum leaves when dissolved in acids. These results are of the 
greatest importance, because they have enriched chemistry with a 
* Only a small number of these have been published. The rest were made for 
private individuals, or for the Administration of Mines. Among the latter are 
those of the French ores of tin, and particularly those of the department of the 
Haute Vienne, the results of which are very important, because they show that 
Francepossesses extensive tin veins, which may be wrought with advantage, 
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