100 



In determining the percentage of bitumen in the refined material 

 by means of solvents it is found that some of the mineral matter 

 passes through the finest filters and is not removed from the solution 

 on prolonged centrifuging. On examination under the ultra- 

 microscope it is revealed that it consists of clay in a colloidal condition, 

 originating in the mineral matter of the mud spring in which it existed 

 in this state as regards the water with which it is associated, and 

 which is introduced into the bituminous phase on the removal of the 

 water on refining. The amount of mineral matter in the colloidal 

 state depends on the concentration of the solution, that is to say, upon 

 its viscosity, as shown by the following data : — 



Characterisation of Solutions of Trinidad Asphalt (T.R.A.). 



Characterisation of Solutions of Trinidad Asphalt. 



Per cent. Concentration. 



Solvent : Benzol — 



1 per cent. (T.R.A. 



Refined, per cent. 

 Colloidal matter. 



Refined, amount 



calculated per 



1 per cent. (T.R.A.). 



2-54 

 1-00 

 0-42 

 0,-27 

 0-16 

 0-14 

 0-16 

 0-21 

 0-35 



In dilute solution it appears that the amount of matter in a 

 colloidal state is comparatively smaU, but with increased concentration, 

 that is to say, with increased viscosity of the continuous phase, it 



