206 ASPHALT. 



as are known to occur in many parts of the world. Again the 

 mineral matter in its colloidal state may be produced in another 

 way : Warm alkaline water dissolves silica ; if it is made acid it 

 loses its solvent power, so the silica is precipitated in so finely 

 divided a state that it is gelatinous. The quantitative analysis 

 of silica is based on this same principle. Now the water in the 

 soft pitch as it rises near the centre of the Pitch Lake is alkaline 

 (Clifford Richardson, Pop. Sci. Monthly, July- Aug., 1912), but 

 in the crude asphalt it is acid (C.R. ibid), giving just the con 

 ditions requisite to produce colloidal silica. 



Within recent years a high grade asphaltic petroleum has 

 been found about 2,000 feet deep in the vicinity of the Pitch 

 Lake, which is doubtless the source of the lake. Let us apply 

 then the foregoing to the formation of Trinidad asphalt in the 

 theory as outlined by Clifford Richardson. The depression in which 

 the Pitch Lake occurs was probably in olden times just such a 

 mud spring as is described above, erupting under great pressure. 

 Then the petroleum under its own gas pressure broke through into 

 the friable stratum of clay, finally reaching the vent through 

 which the hot mud spring was forcing its way. There it was mixed 

 and thoroughly churned on its way to the surface, so that it 

 became an intimate emulsion of oil, mud and alkaline mineral 

 water, the various component parts being admitted to the mixture 

 in definite amounts according to the various sources of supply and 

 their pressure. The presence of water in the mud tends to prevent 

 any excessive heat, and it is probably not in the vapour phase 

 because of the great pressure which brings the material to the 

 surface against the weight of a plastic mass of asphalt over 150 feet 

 deep, which it keeps in constant motion. 



The conditions as postulated above are similar to those in an 

 oil refinery, producing what is known as B.S. (Bottom Sludge), an 

 emulsion of oil and water formed by the churning action of steam 

 on hot oil in the condensers, and there cooled. It is well known 

 and severely anathematized by every oil man ; similarly Trinidad 

 asphalt. 



The petroleum mentioned above as being the source of 

 Trinidad asphalt is unique in its structure inasmuch as the removal 

 by heat of a small fraction at a low temperature leaves a residue 

 which is a liquid asphalt, there being no intermediate fractions 

 (kerosene, neutral and gas oils) between the light naphtha and the 

 lubricating oils, so that a low temperature only is necessary to 

 reduce the crude petroleum to a liquid asphalt. Thus it happens 

 that the crude oil emulsion readily loses its lighter portions by a 

 species of film distillation from the hot colloidal particles, whereby 

 a small amount of heat is enabled to do a large amount of volatili- 

 zation in reducing an oil to a hard asphalt. 



Though it begins to melt about 180° F. it does not become 

 properly liquid till about 300° F. It has a consistency of 4° by 

 the penetrometer, and since this is harder than it would ever be 

 used in that condition it is softened by the addition of an asphaltic 

 flux to any degree of softness desired to suit conditions of traffic. 



