from Nalkre Molybdevia. 203 



and reduce it to powder; introduce it into an inclined re-, 

 toi t, and torrefy it, to separate the sulphur, and to oxygenate 

 the metal, m a heat which must be immediately raised to a 

 very high des:;ree. When the molybdena has lost its bril- 

 liancy, and ils black colour has changed tc gray, lessen the 

 heat, and continue to expel the last portions ol the sulphur, 

 and to complete the oxygenation oi the metal at a more 

 moderate heat, continually stirring the matter wah an iron 

 spatula. By these means the matter will be prevented from 

 entering into fusion with the oxide ot' iron and a small 

 quantity of aluminc with A\hich they are mixed, and from 

 forming a mass which the anunonia can afterwards dtcom- 

 pose only with difficulty, and nothing will rcmaui adhering 

 to the crucible. The mineral is then to be reduced to a very 

 fine powder, and it must be diecsted several times with a 

 suliicient quantity of liquid ammonia to extract the whole 

 molybdic acid. The diiferent liquids are then to be united, 

 and being poured into a glass retort are distilled to dryness. 

 Molybdate of ammonia will remain in the retort. The heat is 

 increased to incandescence, in order to expel the ammonia. 

 If the retort be too large, the matter must be removed into 

 a smaller. 



This process would not answer where it is required to 

 analyse ore of molybdena. In this case it would be neces- 

 sary to oxygenate the sulphur and the metal by the help of 

 nitric acid. This meihod will contribute in ail probability 

 to ameliorate and render easier the analysis of sulphuret of 

 molybdena. 



Addition to the preceding Experimevts. 

 I had undertaken four times, and with the same success,, 

 the separation of the molybdic acid by the help of ammo- 

 nia in the proportions of experiment XIV, when in treat- 

 ing in this manner a pretty large quantity of calcined ino- . 

 lybdena I observed a surprising ) ha-nomenon which hi- 

 therto I had not remarked. I separated the acid fiom two 

 ounces of molybdena by the help ol ammonia. The filtered 

 liquor was left at rest for some days, to see v.hether any 

 thmg would be deposited ; which actually was the case. 

 Some flakes which cxhibitLd the same pha:nomena as oxide 

 of iron weie dejiosited. I again placed the liqupr on one 

 side, to see whether a new separation would lake place. I 

 had, however, evaporated and decomposed a quantity of 

 the solution of molybdate of ammonia equal to a sixteenth 

 part of the whole liquid. The residuunr exhibited tlic •^ame 



phienoniena 



