101 



becomes progressively larger until in the refined asphalt itself all 

 of the mmeral matter, at ordinary temperatures, may be regarded 

 as in a colloidal state. Trinidad asphalt appears, therefore, to be 

 a material the components of which are in a state of equilibrium, 

 and this accounts for its uniform composition. It is, therefore, a 

 unique material, and it is to the large amount of surface energy 

 developed by the liighly divided mineral matter which it contains 

 that the demonstrated industrial value of the asphalt is to be 

 attributed. 



•. The Introduction of Colloidal Clay into the purer forms of Bitumen. 



In the light of the preceding facts the inference was drawn by 

 the writer that c\a,j in a coUoidal state might be introduced in a 

 similar manner, industrially, into the purer forms of asphalt, and 

 into the residual asphalts prepared from petroleum. For this purpose, 

 a paste of clay and water, in which the clay was in a colloidal state 

 as regards the water, was emulsified with residual asphalts from various 

 tjrpes of petroleum. The water was then driven off at high tempera- 

 tures and it was found that the relation of the clay to the bitumen 

 became a coUoidal one. The proportions were so selected that the 

 resulting material, after the removal of the water, should consist of 

 67 per cent, bitumen and 33 per cent, of clay. These materials were 

 then maintained in a melted condition in tubes for 24 hours, at a 

 temperature of 325° F. The sedimentation which ensued, with the 

 reduction of the viscosity of the continuous phase at this high tempera- 

 ture, varied with the different residuals, and was as follows :■ — 



It is apparent from the preceding data that the colloidal capacity, 

 if it may be so designated, of the different materials is characteristic 

 of the particular bitumen and of its viscosity at a definite temperature. 

 The various bitumens are, in this way, very plainly differentiated. 



Industrial Application. 



Industrially these observations are of importance, especially in 

 the construction of asphalt pavements, such as that laid on the 

 Victoria Embankment in London. The mmeral aggregate of this 

 surface consists of fine sand, a filler for the voids in the sand, 



