igfi Method qJ' extracting MohjhJic Acid 



When the ^-holc quantity of niolybdena was introduced, i 

 ver\' brisk def]aii;ration took place. I dissolved the saUne 

 mass in distilled water. The whole dissolved except about 

 ten gros, which were oxide of iron and silex. The ley fur- 

 nished by crystallization a little undecomposed saltpetre, 

 nitrite of potash, and gaso-nitrous sulphates and molyb- 

 dates of potash, or holdmg nitrous gas. 



These experiments prove that 2|- parts of nitre are suffi- 

 cient to deprive of its sulphur one part of sulphurated mo- 

 lybdena, and to oxygenate the metal. This quantity might 

 even be diminished, were it not to be apprehended that the 

 small portion of undecomposed sulphur which is found in 

 the mass towards the end of the operation would with diffi- 

 culty be attacked by too small a quantity of nitre. 



To find the means of separating the molybdic acid from 

 the acidulous molybdate of potash thus obtained, I mads 

 the following experiments. 



Experiment III. 



To a portion of the above solution I added sulphuric acid 

 till nothing more was precipitated and the mixture had ac- 

 quired a stroni!;lv acid taste, after which it was digested cold 

 for two hours. The precipitate obtained was washed several 

 times with distilled water, and it was heated with twenty 

 parts of the same water. The whole of it readily dissolved. 



To this solution I added nitric acid until there was a con- 

 siderable excess. No precipitate was formed. I evapo- 

 rated the liquor to dryness. The residuum contained no 

 crystallized part, had no taste of saltpetre, and did not de- 

 flagrate when tin-own on burning coals. This residuum, 

 which was vellow, easily fused in an ignited crucible with- 

 out being evaporated by a strong heat. After cooling, it 

 was found to have assumed a yellower colour. This ex- 

 periment evidently proves that acidulous molybdate of pot- 

 ash is not decomposed either by sulphuric acid assisted by 

 a digesting heat, or by nitric acid; for the precipitate ob- 

 tained was exceedingly soluble, ?ind was not volatile at a 

 white heat. 



As I had e^'aporated the solution of molybdate conjointly 

 with nitric acid, it was possible that the nitrate of potash 

 formed in the first instance might afterwards be decomposed 

 hx the m(jlyi)dic acid separated. I therefore resolved to re- 

 peat the same operation with nitric acid. 



Experiment IV. 



• I decomposed a part of the above solution of acidulous 



molybdate. 



