56 URANIUM, ANTIMONY, CHROMIUM, & c 



protoxide has a brown colour ; the deutoxide, or 

 molybdous acid, has a purple colour when anhy- 

 drous, but a beautiful indigo blue when mixed 

 with water. The peroxide, or molybdic acid, is 

 white, or when hot, yellow. 



1. Bucholz found that 100 parts of molybde- 

 num, when converted into molybdic acid, unite 

 Atom of w ith 49 or 50 parts of oxygen. Now, if this acid 



molybde- A 



num and be a compound of 1 atom metal + 3 atoms oxy- 

 adcu gen, (as is likely, from the existence of three ox- 

 ides of molybdenum) it will follow, that the 

 atomic weight of molybdenum is 6, and that of 

 molybdic acid 9. For 50 : 100 : : 3 : 6. 



To verify this estimate, I exposed a quantity 



of molybdate of potash to such a temperature as 



I knew, from previous trials, was sufficient to 



Analysis of drive off all the water of crystallization. Fifteen 



molybdate / i 11 i TII 



of potash, grams or this anhydrous salt were dissolved in 

 water, and mixed with a solution of 20*75 grains 

 of anhydrous nitrate of lead : a double decompo- 

 sition took place ; and molybdate of lead preci- 

 pitated in the state of a white powder. The 

 supernatant liquid was colourless, and was neither 

 affected by sulphate of soda nor by nitrate 

 of lead ; showing that it contained no sen- 

 sible quantity either of lead or of molybdic 

 acid. 



We see from this experiment, that 15 grains 

 of anhydrous molybdate of potash contain just 

 the quantity of molybdic acid necessary to satu- 



