it's properties and composition MUNRO 23 



composition of the sample of Blue analyzed, but for the anhy- 

 drous gel, the formula is, no doubt, M03O8. 



It would be interesting to note whether the variation in 

 composition of the precipitated ammonium phosphomolyb- 

 dates, which "seem to violate the constancy of composition 

 test for distinguishing compounds from mixtures," could not 

 be explained in a similar manner. Possibly the variation is 

 due to the adsorption of water or an oxide by the ultramicrons 

 the amount of which varies with conditions. 



The formation of Molybdenum Blue by the action of am- 

 monium molybdate and a stannous salt is a sensitive test for 

 tin. An attempt was made to determine the sensitiveness of 

 the test for tin. 



Stannous chloride was obtained by dissolving ."2138 g of 

 pure tin in C.P. HCl. The solution was diluted to 500 cc and 

 50.01 cc of this solution diluted to 500 cc. A tin bead was drop- 

 ped into the resulting solution and the solution immediately 

 titrated against an approximately 1/5% solution of Ammonium 

 molybdate. 



1 cc tin 



Average ratio -— , ., , 



60.1 cc sol. AM 



c • . . -2138^ 1 1 



oensitivity = X 



^ 5000 600 1.423.000, 



(Some error due to SnCli— >■ Sn CI4.) 



Sensitivity of test for Molybdenum was also tried. It 

 could not be determined with any degree of accuracy, owing to 

 the formation of the green solution, when Sn CI2 was in excess. 

 This faint green color was very hard to detect. 



Summary of Findings or Confirmations 



1. Blue is most readily prepared by action of SnCU and 



H.S. 



2. Green and brown colors are due to further reduction com- 



