from Native Mohjldena. lOy 



and Heyer*, in which calcined molybdena exhibited the 

 phasnomena of an acid, made me suspect that this molyb- 

 dena might be molybdic acid like that sublimated. In this 

 case the nitric acid might have been spared; which would 

 have rendered the process still shorter and more cecono- 

 )niral. 



To clear up my doubts in this respect I made the follow- 

 ing preliminary experiments. 



Experiment VII. 



I reduced to fine powder some grains of calcined molyb- 

 dena, poured over it a gros of water, and heated it above a 

 lamp. I then instilled into it some drops of a solution of 

 carbonate of soda : on each new instillation a strong effer- 

 vescence took place, and a g^reat part of the matter was dis- 

 solved. For the moment this result was sufficient to en- 

 able me to conclude from it the acid nature of the calcined 

 molybdena. The solution was filtered, and decomposed by 

 nitric acid. There was formed a precipitate of molybdic 

 acid, which placed it beyond a doubt that there was formed 

 a combination of this acid with soda. 



Experiment VIII. 



I pulverized some grains of calcined molybdena, and 

 boiled them for some minutes with an ounce of water. The 

 taste of the liquor, which was sensibly acid and metallic, as 

 well as the red colour it communicated to turnsole paper, 

 again proved the nature of the acid of calcined molybdena. 



It gave me great satisfaction to have found so short and 

 so oeconomical a method of obtaining molybdic acid. I can- 

 not help wondering, as the experiments of Scheele, Heyer, 

 and Ilseniann, have been so long known, that chemists have 

 not followed this method indicated to us by the nature of 

 calcined molybdena, and to v.hich they had so nearly ap- 

 proached. In order to ascertain more fully whether cal- 

 cined molybdena is pure molybdic acid, and to determine 

 the means of separating from it the heterogeneous sub- 

 stances with which it nught be still combined or mixed, I 

 made the following experiments. 



Experiment IX. 



As the molybdic acid has the property of combining 

 easily with a portion of potash, and of retaining that base, 

 it not entirely, at least in a great part, against the action of 

 all acids, this salt could not be of any use for purifying that 



* Crcll'i Clicmischc Annalcn, vol. ii. p. 26 and 125. 



N 1 acid. 



