202 P>'°f' Berzelius on the Discovery of a [April, 



city of saturating acids, in which it even surpasses magnesia. 

 We have called it lithion, to indicate that it has been discovered 

 in the mineral kingdom, while the two others are of vegetable 



origin. 



Another discovery no less interesting is, that the information 

 which I gave you in my last letter, respecting the discovery of 

 tellurium in sulphur procured from the mine of Fahlun, which is 

 employed in the manufacture of sulphuric acid at Gripsholm, 

 appears to be incorrect. I have just been making a more accu- 

 rate examination of it at Stockholm, and I have found that what 

 M. Gahn and I took for tellurium is a new substance possessed 

 of very interesting properties. This substance has the properties 

 of a metal, combined with those of sulphur, to so great a degree, 

 that it might be supposed to be a new species of sulphur. The 

 following are some of its properties. In its metallic state, it has 

 a brilliant metallic lustre on the external surface with a tinge of 

 red • the fracture is vitreous, like that of sulphur, but with a very 

 brilliant lustre, of a grey colour. At the temperature of boiling 

 water it is softened, and at a higher temperature it melts ; it may 

 be distilled at a temperature approaching to that of boiling mer- 

 cury. Its gas, with which the heated part of the vessel may be 

 tilled, is yellow, exactly like that of sulphur. If it be sublimed 

 in a laro - e vessel, it is deposited in the form of flowers, of the 

 «olour of cinnabar, which are not, however, in the state of an 

 oxide. During its cooling it preserves for some time a certain 

 degree of fluidity, so that it may be moulded between the fingers 

 and be drawn into threads. The threads, when drawn out to a 

 great degree of fineness, if held between the eye and the light, 

 are transparent, and of a ruby colour ; while by reflected light 

 they exhibit a brilliant metallic lustre. When this new substance 

 is heated by a candle, it burns with an azure-blue flame, and 

 exhales a strong odour of horseradish, which led us to suppose 

 that it was tellurium. It is not easy to produce this odour from 

 purified tellurium, either because it does not belong to it, except 

 in as much as it contains this new substance, or because it is diffi- 

 cult to make it undergo the change which is necessary to pro- 

 duce this odour. The analogy of tellurium has induced me to 

 give it the name of selenium. 



Selenium combines with metals, and generally produces a red- 

 dish flame. The alloys have commonly a grey colour and a 

 metallic lustre. The selenuret of potassium dissolves in water 

 without evolving any gas, and produces a fluid of a red colour, 

 which has the taste of the hydrosulphuret of potash. If we pour 

 diluted muriatic acid upon the selenuret of potassium, a selenu- 

 retted hydrogen gas is disengaged, which is soluble in water, 

 and precipitates ail metallic solutions, even those of zinc and 

 iron. The gas has the odour of sulphuretted hydrogen gas, 

 when it is diluted with air; but if it is breathed less diluted, it 

 produces a painful sensation in the nose and a violent inflamma- 



