r22 EXPERTMENTS ON MtJLYBDEXA^ 



Constitution of very of Scheele. If any one doubt of this, he has only to 

 «in the native ^^^ ^^ ^^,^ ^^^^^ ^-^^ different elementary works we have on 

 state douoted. ^ - . •' 



chemistry, to be convinced of it. Who would not be sur- 

 prised to see cherliists still in doubt respecting the composi- 

 tion of molybdena us it is found native? Some consider it 

 as a sulphuret, in which the inolybdena is in the metallic 

 state; while others assert, that they cannot find a particle of 

 sulphur in it, and look upon it as a native molybdena. The 

 smell alone however is sufficient, to convince us of the pre- 

 sence of sulphur in it. Let any one heat laminse of the 

 purest molybdena, the sulphurous smell, that will exhale, 

 must prove to him, that it contains sulphur, if he have not 

 lost the sense of smell. 

 Proportion of Farther we are ignorant of the proportion in which oxi- 

 acid unknown. »^^ ^^ combined with the metal to form molybdic acid». 

 though it has been so long known. The want of positivef 

 knowledge on these points has led. me to think, that, if I 

 were to undertake a series of experiments on molybdena, I 

 should attempt a task of some utility, and that would con- 

 tribute to augment and improve our knowledge of this sub- 

 stance. To my friend Mr. Haberle I am indebted for the 

 quantity of molybdena, that has enabled me to make these 

 experiments. 

 First the exist- The first thing to be done was, I conceived, to remove all 



ence and quan- (jgy'i^^. respecting; the presence of sulphur, and to determine 



tity of sulphur , ' '^ . : . r ? 



tobeascer- its quantity. This I imagined would best be effected, by 



tamed. oxigenizing both the sulphur and the molybdena, and sepa- 



rating by means of barytes the sulphuric acid formed. But 

 it was necessary previously to ascertain, whether the molyb- 

 dic acid, which also forms a salt of no great solubihty with 

 barytes, would not occasion some errour in this computa- 

 tion. 



I. Experiments to determine the composition of the native 

 sulphuret of molybdena. 



The native sul- Exp. 1. Twenty-five grains of very pure chosen molyb- 

 taiusno t'xcess ^^^'^ '^'iGxa reduced to a fine powder, and heated quickly in 

 of sulphur, & a small glass matrass. No sulphur was disengaged. The 

 nooxigen. matrass when cooled contained a little sulphurous acid va- 

 pour, and the molybdena, which had been heated red hot, had 



scarcely 



