14 MOLYBDENUM BLUE 



mondy says: "Colloids can be completely remo\x"d from a liquid 

 by porous bodies. As a lecture experiment the author has used 

 the absorption of Molybdenum Blue by animal charcoal. As 

 in other cases the absorption was quantitative and irreversible." 



It was found however, that if the solution was filtered as 

 soon as it became colorless and the filtrate treated with SnCU, 

 a slight blue coloration was obtained. This shows that it 

 is incorrect to assume, as Zsigmondy evidently does, that the 

 bleaching action is wholly due to absorption. The action is 

 also one of oxidation, although to a much smaller extent. 



The oxidizing power of charcoal was shown by treating the 

 brown solution obtained from the extreme reduction of Blue 

 by Zinc. The supernatant liquid gradually changed to blue. 



Vectoriality. — Some liquids are vectorial in character. 

 They form "crystals" while still in the liquid, i. e., they assume 

 definite shapes. Extensive research has been done on this 

 property of liquids. The question as to whether, or not, col- 

 loided phases exhibit vectorial properties, has apparently not 

 been settled to the satisfaction of all, as yet. However, men 

 who have worked upon this problem usually support the affirma- 

 tive. To quote Lincoln ("Physical Chemistry," 1920): 



"Von Weimarn even believes vectoriality is manifested 

 by gaseous substances and in addition, has presented evidence 

 which he considers to be direct proof of the vectorality of the 

 colloid phases. In the case of colloid iodine and certain colloid 

 dyes, L. Pelet and Wild claim to have observed the fusion of 

 ultra-microscopic particles which assumed definite crystalline 

 shapes." 



An attempt was made to obtain crystalline Molybdenum 

 Blue and thus confirm the work of Von Weimarn and Pelet 

 and Wild. 



Microscopic slides were placed in shallow evaporating 

 basin, containing filtrate from Blue prepared with SnCh. 

 The solution was allowed to evaporate at room temperature. 

 When slide became exposed it was removed and allowed to 

 dry. It was examined under the microscope. 



