MOLYBDENUM. 57 



rate the protoxide of lead in 2O75 grains of ni- 

 trate of lead. But 20 'J5 grains of nitrate of lead 

 contains 14 grains of protoxide of lead, which is 

 equivalent to an atom : 15 grains of anhydrous 

 molybdate of potash, therefore, contains a quan- 

 tity of molybdic acid equivalent to an atom. It 

 must be in combination with an atom of potash. 

 But as an atom of potash weighs 6, and the salt 

 15, it is plain that the weight of the atom of 

 molybdic acid must be 9 ; and the anhydrous 

 salt consists of 



1 atom molybdic acid . 9 



1 atom potash . . 6 



15 



The molybdate of lead being collected and dried, 

 weighed 23 grains. Now, it contained 14 grains 

 of protoxide of lead ; consequently, its constitu- 

 ents are 



1 atom molybdic acid 

 1 atom protoxide of lead 



2. Molybdate of potash crystallizes in small 

 four-sided right prisms, terminated by rhombic 

 bases. Its colour is white, with considerable 

 lustre ; it is opaque, and has a taste that puts 

 one in mind of that of a weak solution of potash j 



