EXPERIMENT^ ON MOLYBDENA. JQ^ 



From the experiments on the blue oxide, that have been General re- 

 related, we may deduce the following results. ^"''^• 



1. Several of the degrees of oxidation before observed 

 have been confirmed, and some others discovered. In the 

 experiments made on metallic molybdena I have frequently 

 remarked, that its surface lost its splendour, and seemed to 

 become coated with a gray matter. 



This is certainly a commencement of oxidation, and is Different 

 the first stage : the brotcn oxide is the next: and this passes, ^^^f^^ °^ °^^' 

 as has been said, by boiling to the blue; which may likewise 

 be produced by heating the metal, or by heating the brown 

 oxide obtained by the decomposition of the molybdate of 

 ammonia; and it appears, that the substance produced by 

 these two different operations may be considered as identi- 

 cal. After the blue oxide we have the blueish green, which 

 may be produced by boiling the blue, or leaving it exposed 

 some time to the air: and the contact of metallic molyb- 

 dena, or the action of pure ammonia, will bring this back 

 again to the state of blue oxide. Lastly the blueish green 

 oxide passes to yelloiv, and afterward to white, which is the 

 inolybdic acid. The transmutation of the blue oxide into Alkali pro- 



the last two is sing-ularly promoted by the presence of an mo'es a higher 



^ J ^ J r oxidation, 



alkali. 



2. The white molybdic acid placed in contact with the Molybdic acid 

 brown oxide, or with metallic molybdena, divides its oxigen converted lo 

 with them, and thvis passes to the state of blue oxide. The 

 blue colour, that molybdic acid acquires on the addition of 

 a metallic solution, as remarked by Scheele, Heyer, and 

 Ilsemann, is an effect of a similar disoxigenation. Other 

 disoxigenizing circumstances may occasion the conversion of 

 the molybdic acid to the state of blue oxide, as for instance 

 the passing of ammoniacal gas over it. 



After having discovered these different degrees of oxida- Proportions of 



tion, it appears an object to ascertain the proportion of °^'S='' ^^V.'^' 

 , , . , rrii • T 1 11 -1 lect of farther 



oxigen to the metal m each. 1 nis 1 shall pursue with some inquiry. 



other inquiries, when I have procured a sufficient quantity 

 of the ore of molybdena. The principal subjects of my 

 research will be the blue and the brown oxide, as tljey are 

 the most stable, and are most easy to procure in large quan- 

 tity and unmixed : but what renders them particularly in- 

 O 2 teresting 



