422 MM. Svanberg and Struve on the Atomic Weight 



gave after reduction 0*5195 grm. When the reduction was 

 complete, which was indicated by the weight remaining con- 

 stant, the residue was exhausted with water, which dissolved 

 a portion, forming a colourless liquid ; the insoluble portion 

 was collected on a filter. To the naked eye some portions 

 of the residue present a strong lustre and a tomback-brown 

 colour; this is still more distinct under the microscope. The 

 filtered solution was evaporated in a counterpoised crucible, 

 ignited and weighed. The salt forms a white powder, behaves 

 like the neutral molybdate of potash, and weighed 0*2496. 



100 parts of the trimolybdate of potash consequently lose 

 on reduction — 



5*973 oxygen, and yield 

 45*176 neutral molybdate of potash and 

 48*851 insoluble oxide (estimated from the loss). 

 If we compare this with theory, we find that 



I at. KaO, 3Mo03 + , at. HO is f J £ £g- J** 



decomposed into 1 _ HO 



which gives in 100 parts — 



a. b. 



Oxygen 6*143 . . 6*218 



KaO, MoO 3 .... 45*391 . . 45*539 



MoO, MoO 3 . . . 48*466 . . 48*243 



100*000 100*000 



When the insoluble oxide which has been freed by water 

 from the neutral molybdate of potash is heated with a solution 

 of caustic potash, a large quantity of molybdic acid dissolves. 

 The same occurred on boiling it with muriatic acid ; however, 

 it was far less violently acted upon by the latter. These ex- 

 periments indicate that molybdic acid exists in the insoluble 

 oxide, and we have on that account admitted the formula 

 MoO, MoO 3 , and not the formula 2M0O 2 , both which for- 

 mulae express the same relation between the oxygen and mo- 

 lybdenum ; it is however possible that by the action of the 

 potash, the insoluble residue may have passed into molybdic 

 acid, either by re-arrangement of the elements, or from having 

 absorbed oxygen from the air. Nitric acid readily converts 

 it into molybdic acid. 



By the careful addition of nitric acid to a solution of mo- 

 lybdic acid in carbonate of potash, the previously-described 

 double salt is precipitated ; on using a large excess of nitric 

 acid, however, the phaenomena are totally different. In this 

 case a very bulky precipitate is instantly produced, which 

 gradually increases. But in this precipitation different cry- 



