20 Berzclliis on a new Mineral Bodi/, [Jan. 



reason, may be considered as oxides, which it has been hitherto 

 impossible to reduce ; while the third has a problematic exist- 

 ence. These bodies are chlorine, iodine, and fluorine. To render 

 the simplicity of these bodies more probable, advantage has been 

 taken of their supposed analogy with sulphur and phosphorus. 

 It is evident that in proportion as more bodies are discovered 

 and compared with these last, this analogy must either increase 

 or d^iminish in probabilit}\ This is the reason that induces me 

 to compare selenium with sulphur, chlorine, iodine, and some 

 other bodies. 



Sulphur and selenium, on one side, unite with the metals; and 

 these combinations, which, for the most part, still preserve some 

 of the external properties of metals, retani likewise the combus- 

 tibility of their radicals. The sulphuret and seleniuret of 

 potassium and sodium are soluble in water. They decompose it 

 at the same time, and produce hydrosulphurets and hydrosele- 

 niurets. 



Chlorine and iodine, on the other side, combine likewise with 

 the metals ; but their combinations have generally the same 

 characters as the anhydrous sulphates, phosphates, and arse- 

 niates. The radicals, at least the most combustible, have lost 

 their combustibility : the chloride and iodide of potassium and 

 sodium do not unite with oxygen ; do not decompose water ; 

 and do not form hydrochlorates and hydriodates (unless it be 

 pretended that the chlorides of potassium and sodium decom- 

 pose v.'ater v.ith the production of cold ; while the chlorides of 

 calcium and barium decompose it and produce heat). On the 

 contrary, the chlorides of copper, tin, and gold (and of several 

 Other metals, which are incapable of decomposing water, either 

 alone, or in the state of sulphurets, or mixed with the strong 

 acids), decompose water, and produce hydrochlorates. There is, 

 therefore, no analogy between sulphur and selenium on the one 

 side, and chlorine and iodine on the other, since they produce 

 entirely opposite phenomena. 



Sulphur, selenium, and tellurium, combine with hydrogen, and 

 produce particular acids, which are gaseous and very weak. It 

 had been long observed that sulphur and tellurium, notwithstand- 

 ing the difference in their physical and chemical properties, form 

 ■ combinations v.ith hydrogen of characters astonishingly analo- 

 gous. We now find a third body with v.'hich hydrogen forms 

 -a compound, having the same smell, the same taste, and the 

 same properties, as the two preceding ones. This class of acid 

 bodies gives with all the oxides, whose radicals have a stronger 

 affinity for oxygen than hydrogen has, a particular kind of salt, 

 which preserves the taste, and in part even the odour of the 

 acids ; though they are less capable of neutralizing the bases 

 than other acids. The oxides, whose radicals have a weaker 

 affinity for oxygen than that of hydrogen, are decomposed by 

 these acids. The result is water, and a combination of the radi- 



