I«? 



1818.] the Commencement of the Year 1817. Part I. \\ 



substance was observed by M. Alluaud. It was black, had a 

 certain metallic brilliancy, and was ramose. Gay-Lussac found 

 it composed of pure carbon. The metallic carbon of Dbbereiner, 

 he found, left a residue of 25 per cent, of iron and silica. Hence 

 it is obviously a carburet of iron and silicon. — (Ann. de Chim. et 

 Phys. iv. 67.) 



4. Selenium. — This is a new metallic substance, possessing 

 several characters similar to those of sulphur, and others to those 

 of tellurium ; for the knowledge of which we are indebted to the 

 sagacity and good fortune of Professor Berzelius. 



This new substance, which unfortunately is very scarce, was 

 discovered in the following manner. There is a manufacture of 

 sulphuric acid at Fahlun in which the sulphur employed is 

 extracted from the copper pyrites of that celebrated, mine. 

 Berzelius and Gahn lately purchased a share of this manufacture; 

 and on examining the process, they were struck with a red 

 matter which remained in the leaden chamber in which the 

 sulphur was burned. When this substance was heated, it gave 

 out a strong smell of horse-radish, which induced them at first 

 to believe that it contained tellurium ; but Berzelius took a 

 quantity of it to Stockholm, and examined it more carefully. He 

 succeeded in separating it from the sulphur with which it was 

 combined, and ascertained that it possessed new and very pecu- 

 liar properties. He gave it the name of selenium, from the 

 analogy which it has to tellurium. Its properties, as far as they 

 have been made known to us by Berzelius, are as follows : 



Its colour is grey, with a strong metallic lustre ; its fracture 

 is vitreous, like that of sulphur, or like that of fahlore, of which 

 it has the colour, though its lustre is much more considerable ; 

 its specific gravity is about 4-6 ; it is hard, but very easily 

 frangible, like sulphur ; when reduced to powder, it has a red 

 colour, with here and there a metallic lustre, as is the case with 

 the other brittle metals. 



It softens at the temperature of boiling water, and melts 

 when the heat is raised a little higher. During its cooling it 

 preserves a kind of ductility, like sulphur or Spanish wax ; so 

 that it may be kneaded between the fingers and drawn out into 

 fine threads which have a strong metallic lustre. When held 

 between the eye and the light, these threads are transparent, and 

 appear of a dark red colour. At a temperature nearly approach- 

 ing the boiling point of mercury, selenium boils, and may be 

 distilled over in opaque, metallic drops. The retort becomes 

 filled with a yellow vapour, quite similar to that of sulphur ; but 

 not so intense. When distilled in a retort with a large neck, it 

 sublimes in the form of flowers, of a fine cinnabar colour. These 

 flowers are not in the state of oxide, and are converted into the 

 usual greyish mass by simple fusion. When sublimed in the 

 open air without taking fire, it evaporates in a white smoke, 

 which is destitute of smell ; but when held in the flame of a 



