ON MOLYBD.ENA 175 



attracts phlogiston from the charcoal powder that is added ; 

 but alkali prevents as much earth from entering into this 

 union as is necessary to its saturation. It appears from 

 Sec. x. (3), that alkali more strongly attracts the earth than 

 the earth does phlogiston. This is a neutral salt, which is 

 soluble in water, and is entirely like the salt of Sec. vu. (//) ; 

 the charcoal which remains after the lixiviation yields 

 vapours in an open crucible, and gives a sublimate con- 

 taining phlogisticated earth of manganese. (3) This alkali 

 fixes the earth in the open fire (Sec. xi. (4)). (4) Hence 

 appears likewise the reason why this earth does not expel 

 the vitriolic acid from vitriolated tartar; for its attractive 

 power for the alkali must diminish in proportion as it comes 

 nearer to the point of saturation ; and as the pure earth 

 contains no alkali, it attracts a little from the vitriolated 

 tartar, consequently there can appear but a slight vestige of 

 vitriolic acid (Sec. vm. (d)). This small quantity of alkali 

 occasions its more easy solubility in water. The same earth 

 is found in Sec. vu. (c). 



SECTION XIII. 



Having now analysed molybdaena, by means of the 

 experiments which I have communicated, it still remained 

 to be able to recompose this mineral of its proximate con- 

 stituent parts. That molybdoena contains sulphur is already 

 known, and my experiments show the same thing. Some 

 very fine pulverised earth of molybdoena (Sec. vi. (c)) was 

 mixed with three parts of sulphur. The mixture was 

 distilled in the open fire in a glass retort, furnished with a 

 luted recipient. The retort was placed in the beginning in 

 such a manner that the sulphur which rose to the neck 

 should run back again : but at last this substance was 



