1820.] Royal Academy of Sciences. 375 



gravity is 3*6. It produces a red powder by trituration, is 

 softened at the temperature of boiling water, a little above which 

 it melts ; and, while cooling, it remains for some time soft, 

 plastic, and capable of being drawn out into threads in the same 

 manner as seahng wax. At a temperature a few degrees higher, 

 it boils, and sublimes in the form of a yellowish gas, and con- 

 denses into beautiful red flowers, without undergoing oxidation. 

 It evaporates in the open air in a red smoke, and bums with a 

 blue flame, exhaling so strong a smell of horseradish that the 

 thirtieth part of a grain is sufticient to infect the air of the 

 largest room. 



Prof. Berzelius has given the name of selenium, derived from 

 the Greek name of the moon, to this substance, that we may 

 recollect the affinity it has with tellurium ; an affinity which may, 

 perhaps, only arise from the presence of selenium itself in every 

 specimen of tellurium hitherto examined. 



These discoveries having been announced to the Academy by 

 M. Gillet-Laumont, and soon afterwards confirmed by a letter of 

 Prof. Berzehus written to iM. Berthollet, M. Vauquelin imme- 

 diately set about verifying the report with respect to the alkali ; 

 and his observations have added some details to those which 

 INI. Arfvedson had given. Although M. Vauquelin had only a 

 small quantity of petalite at his command, he found in it as much 

 as seven per cent, of lithion. 



Prof. Berzelius has followed up his discovery of selenium with 

 the great care that it merited. He has treated it with most of 

 the chemical agents, and examined their actions upon it ; and, 

 having come to Paris this year, he has given a very detailed 

 account of his labours in the Annales de Chimie. He shows 

 that, taking every circumstance inlo consideration, selenium is 

 an intermediate substance between the combustible and metallic 

 substances. 



He has exhibited comparisons between selenium, with sulphur 

 and tellurium on the one side, and with chlorine, fluorine, and 

 iodine, on the other : all of them substances which many chemists 

 have lately wished to class along with sulphur, because they 

 yield, like that substance, acids, by being combined with hydro- 

 gen. What we have said on this subject in the analyses of 1813 

 and 1814, in giving an account of the newtheory of Sir H. Davy, 

 respecting those acids which he considers as being formed with- 

 out oxvgen, may be recollected. 



M. Berzelius finding the combinations of sulphur, tellurium, 

 and selenium, with metals and combustible substances, to have a 

 great analogy to one another, and on the other side, that the 

 combinations of iodine and chlorine, with the same substances, 

 liave also a great analogy betwixt themselves and with those of 

 oxygenized acids, though they do not resemble in the least 

 the preceding, concludes from hence, that they constitute 

 two very distinct orders of substances ; and by this he shows 



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