IT S PROPERTIES AND COMPOSITION MUNRO 



17 



particles are cubes varying in color from lightblue to very 

 dark blue, according to their thickness. The light blue 

 ones were examined under crossed nicols. They are isotropic. 

 A basal section of a cubic crystal would give this effect. 



The writer can see 

 no valid reason for con- 

 sidering these crystals 

 other than crystal of 

 colloidal Molybdenum 

 Blue. This fact would 

 lend strength to 

 Wiemarn's and Pelet's 

 supposition that colloids 

 have the property of 

 vectorality. 



Pure crystals of 

 Stannous chloride were 

 dissolved in absolute 

 alcohol. A saturated 

 solution of Ammonium 

 Alolybdate in alcohol 

 was also prepared. Por- 

 tions of the stannous 



Fig. 6 i i • i i • 



chloride sohition were 

 diluted by adding more alcohol. A few drops of this 

 solution were added to the molybdate. A brownish pre- 

 cipitate was obtained. The same experiment was tried with 

 HCl added to the molybdate solution. The same result was 

 obtained. 



The alcohol solution was treated with zinc and sulphuric 

 acid with no apparent reaction. Sulphuretted hydrogen was 

 passed into the solution. A colloidal solution resulted. This 

 solution was fluorescent, giving blueish grey and red by re- 

 flected and transmitted light, respectively. After standing for 

 some hours the solution became a fawn color and a flocculent 

 brownish precipitate similar in color to that obtained by adding 



