of Molybdenum and some of its Compounds. 433 



molybdate of potash with a solution of the nitrate of lead, 

 when a white flocculent precipitate immediately separates, 

 which is very sparingly soluble in water. After washing 

 and drying it forms a white powder, which fuses only at a 

 very high temperature. It appears to contain no chemically 

 combined water, for on ignition it lost only 3*380 per cent, 

 after having been dried at 212°, and this quantity only cor- 

 responds to f atom of water. The analysis of this salt, if 

 it is desired not to employ hydrosulphate of ammonia, is at- 

 tended with several difficulties, as a perfect separation of the 

 molybdic acid from the oxide of lead is impossible. In both 

 analyses we have obtained an excess of lead. We effected 

 the separation by treating the ignited salt in a beaker with 

 sulphuric acid and the application of heat. In the first ana- 

 lysis we attempted to determine directly the molybdic acid by 

 evaporating the sulphatic solution, and subsequent ignition 

 with the addition of a few drops of nitric acid. In this deter- 

 mination it is impossible to avoid a considerable loss. 



Analysis. — I. 0*7367 grm. lost on ignition 0*023, and gave 

 0*6082 sulphate of lead, or 0*4175 oxide of lead and 0*2612 

 molybdic acid. 



II. 1*5436 grm. salt lost on ignition 0*0446, and gave 



1*2609 sulphate of lead = 0*9278 oxide of lead; or in 100 



parts — i. ii. 



Water . . . 3*122 3*638 



Oxide of lead. 60*730 60*106 



Molybdic acid 36*148 36*256 



Admitting the water to be hygrometric, the salt will have the 

 following composition : — 



a. Calc. b. Calc. Found. 



1 at. Oxide of lead 1394-645 61072 1394645 61-425 62704 61-893 

 1 at. Molybdic acid 888-966 38928 875-829 38-575 35-449 



2283-611 100000 2270474 100000 98153 



Salts of Silver. 



Neutral Molybdate of Silver, AgO, MoO 3 .— When a so- 

 lution of neutral molybdate of potash is mixed with nitrate 

 of silver, a yellowish flocculent precipitate is obtained, which 

 gradually becomes darker under the influence of light. It 

 is slightly soluble in water, but readily so in water containing 

 nitric acid. After being washed and dried at 212°, it was 

 analysed by dissolving it in ammonia, and then precipitating 

 the silver as chloride, taking care to add an excess of mu- 

 riatic acid, in order to hold the whole of the molybdic acid 

 in solution. We attempted to determine the molybdic acid 

 directly, by evaporating the filtered solution, expelling the 



