of Molybdenum and some of its Compounds. 533 



protoxide of molybdenum = MoO, MoO 3 . Admitting this, 

 100 parts of molybdic acid should furnish — 



a. b. Found. 



Molybdic oxide . 88*751 88*582 88-34-4. 



Experiment II. — 2*1927 grms. molybdic acid were exposed 

 for nine hours in a current of hydrogen to the most intense 

 red heat that a lamp with double draught is capable of fur- 

 nishing. The loss in this case amounted to 0*3793 or 17 298 

 per cent., and the substance in the bulb had throughout a 

 gray metallic colour, which exhibited merely in the centre 

 of the mass some spots of brown. The loss supposes that 

 2 at. molybdic acid = 2 MoO 3 have been reduced to the 

 state of MoO, MoO 2 ; this formula may also be written Mo 2 O 3 , 

 and it then corresponds to a sesquioxide, such as we find in 

 many metals. It may also be assumed that 4 at. MoO 3 have 

 been converted into 2MoO, MoO 3 , which agrees better with 

 the preceding experiment and with what occurs in treating the 

 acid salts of potash and soda with hydrogen. Whichsoever 

 of these views is admitted, the calculated result always remains 

 the same; and 100 parts of molybdic acid furnish — 

 a. b. Found. 



83*126 82*873 82*702 



If in this experiment 2 ats. molybdic acid have lost 3 ats. 



ill i • i j 



oxygen, and have become converted into the compound 



Mo 2 O 3 , then the atomic weight of molybdenum is 567*137, 



which does not differ much from the atomic weight we have 



arrived at. We did not repeat these experiments, as for 



various reasons they cannot yield results sufficiently accurate 



to base thereupon the determination of the atomic weight. 



We are, however, perhaps justified in concluding from the 



experiments just described, that molybdic acid exposed to the 



reducing influence of hydrogen, at the highest temperature 



which glass is capable of bearing, cannot be reduced to the 



slate of metal, but only to the lowest oxide. 



Experiments with Sulphuretted Hydrogen. 



Although the treatment of molybdic acid and of the neutral 

 and trimolybdate salts of potash with sulphuretted hydrogen 

 gas did not lead to the desired object, they nevertheless pre- 

 sent various interesting phaenomena. 



2*739 grms. of dried and ignited molybdic acid were ex- 

 posed in a reduction-tube to the reaction of dry sulphuretted 

 hydrogen. As soon as the gas came into contact with the 

 acid, heat was evolved and the colour of the acid changed 

 to black, but this soon stopped. If the bulb is now heated, 



