2^2 EXPERIMENTS ON MOLYBDENA. 



Could not be But T could discover no method of collecting- the blue oxide 



cmlm^ofitsso- '" ^^^ P"^'^ ^^^^^ ' ^®'"' '^^^^^' ^ ^^^ evaporated the solution of 

 IkibUity. this oxide, I could not separate the residuum, on account 



of its great solubility, either from the sulphuric acid, or 

 from the alkaline sulphate formed by means of the sulphu- 

 retted alkali- A portion of sulphur too remained in this 

 residuum. It is true the alkalis separated a small quantity 

 of oxide, when the solution was concentrated, but its solu- 

 bility did not permit me to wash what was on the filter. I 

 Blue colour must observe too, that an excess of alkali destroyed the blue 

 ^'^'^ik^t-^ ^^ colour ; consequently it is probable, that it occasioned a 



higher degree of oxidation. 

 Other acids To elfect the separatloa sought, I endeavoured to avail 



iurn the mo- myself oi" the experiment of Scheele and other chemists, 

 ivbdic blue. . . 



namely, that molybdic acid, when dissolved in other acids. 



Muriatic acid, affords a blue liquor. The muriatic acid appeared to me 

 most proper, on account of its volatility. Accordingly I 

 dissolved two drachms of brown oxide, obtained by cal- 

 cining molybdate of ammonia, in moderately concentrated 

 muriatic acid. The solution during ebullition changed 

 from brownish yellow to yellowish green, and lastly to a 



eniuply sepif- *^^*^P blue. I evaporated to dryness, and obtained a mass 



laied. of a dull blue, but I could not free it entirely from the 



acid that adhered to it. On washing it, it was partly dis- 

 solved, and what passed through the filter, as well as what 

 remained on it, contained muriatic acid. If I heated the 

 blue mass move strongly, it became gray, and was deprived 

 of its solubility in water as well as of its muriatic acid. 

 After several imsuccessful trials varied in different ways, I 

 was at length led to the object I sought by the consideration 



Must metals of a simple fact, namely, that a solution of molybdic acid 



..huiS': the assumes a blue colour by the contact of most metals. I 



nuilybdic acid . •' . 



iiiue. conceived it would be the same with molybdena itself, and 



that this metal, participating in the oxigen of the molybdic 



acid, would change it to the state of blue oxide. 



V3 grs. of mo- Exp. 25. In consequence I took twelve grains of metal- 



Jyixlenaand ij^. u^^^iyi^fiena and twenty-four of molybdic acid, reduced 



24 of Its acid -^ 1 , 



in water torm the whole to a very fine powder, and. put this into seven 



biueox.de. ounces of water. After standing ten minutes the liquor 



assumed a blue colour, which grew deeper and deeper. On 



boiling 



