of Molybdenum and some of its Compounds. 537 



perature, and how the compounds so produced behave when 

 heated in a current of carbonic acid. 



The only result which we are at present able to deduce 

 from these experiments is, that although sulphuret of potas- 

 sium is present, the molybdenum cannot be obtained in the 

 state of tersulphuret (MoS 3 ), but that a portion is converted 

 into bisulphuret (MoS 2 ), whilst at the same time a portion of 

 the potassium is converted into a higher sulphuret, and that 

 a certain excess of a higher sulphuret of potassium is requi- 

 site to form a certain quantity of sulphomolybdate of potas- 

 sium, and to retain it as such. 



Experiments to determine the Atomic Weight of Molybdenum 

 by fusing Molybdic Acid with Carbonated Alkalies. 



If only a neutral salt were produced on fusing molybdic acid 

 with an excess of carbonated alkali, the atomic weight of 

 molybdic acid and of molybdenum could be deduced in a very 

 simple manner from the amount of carbonic acid expelled. 

 Starting from this assumption we made the following expe- 

 riments : — 



I. 2' 180 grms. molybdic acid fused with 10*1007 grms. car- 

 bonate of potash, lost 0*6866 carbonic acid. 



II. 1*7112 grrn. molybdic acid fused with 10 9066 grms. 

 carbonate of potash, lost 0*5369 carbonic acid. 



III. 3*135 grms. molybdic acid fused with 93958 grms. 

 carbonate of soda, lost 0*9866 carbonic acid : accordingly, 

 100 parts molybdic acid expel, — 



I. II. III. 



Carbonic acid . . 31*4954 31*3749 31*4705 



And if we calculate from this the atomic weight of molybdenum, 

 assuming the atomic weight of carbon to be 75*12 (a), or 

 75*00 (/3), we have, according to — 



et. /S. 



Experiment I. 573*524 573*143 



Experiment II. 576*858 576*476 



Experiment III. 574*216 573*834 



Mean . . 574*866 574*484 



These experiments were made in the following manner: the 

 alkaline carbonate was heated to redness in a platinum crucible, 

 and after cooling over sulphuric acid, weighed. This was 

 repeated until two successive weighings entirely agreed. In 

 another counterpoised crucible the amount of molybdic acid 

 was weighed off, and a large excess of the alkali shaken into 

 the crucible containing the molybdic acid, the whole mixed 

 with a small platinum wire which had been previously coun- 



Phil. Mag. S. 3. No. 225. Suppl. Vol. 33. 2 N 



