202 ASPHALT. 



the re-clistillation of heavy distillate? from an asphaltic petroleum, 

 when the residue remains as a solid asphalt-like substance. So it 

 would seem that oil asphalt does not occur solely in solution in 

 the same way that paraffin wax may be dissolved in petrol and 

 recovered by beat in original amount, but is partly formed at 

 least, as stated above, by polymerization induced at elevated 

 temperatures. Be that as it may, we cannot refuse to recognise 

 a residua] pitch from an asphaltic petroleum as an asphalt merely 

 on account of its partly pyrogenetic and accelerated origin. 



To the oft-quoted "man in the street" it may be a matter 

 of surprise that there should be any difference between the various 

 kinds of asphalt, but there is as much difference as there is in dif- 

 ferent kinds of wood. If you desired a piece of furniture that 

 would last for a long time you would choose a slow-growing wood 

 like mahogany or oak, rather than a quickly growing one like 

 willow; and a little reflection will show that asphalt is no excep- 

 tion to the general rule that the quality of a product in regard 

 to a special purpose is the effect of the treatment resulting in the 

 perfection attained, and proved by usage. As an example, iron 

 ore is found combined with oxygen as haematite, magnetite, 

 limonite, etc., or with sulphur as iron pyrites. Smelting these 

 ores gives wrought iron; and as such by further treatment it is 

 converted into cast iron and steel. Further addition of other 

 elements to the steel gives a material that is particularly adapted 

 to various usages, such as high-speed cutting tools, automobile 

 parts for toughness, artillery, etc. So it is *een that the treatment 

 of the crude material gives the perfected product for particular 

 purposes. Naturally you would not expect to treat a hydrocarbon, 

 such as petroleum, by a method as seveie as the high temperature 

 of smelting iron; its very nature presupposes as low a temperature 

 as possible being used to complete the reduction to a solid form. 

 The lower the temperature the longer the length of time in pro- 

 duction and the higher the quality attained. 



Native Bitumens according to Clifford Richaidsorr consist of 

 a mixture of native hydrocarbons and their derivatives, which may 

 be gaseous, liquid, a viscous liquid or solid; but if a solid, melting 

 more or less leadily upon the application of heat, and soluble in 

 turpentine, chloroform, carbon bi-sulphide, similar solvents, and 

 m the malthas or heavy asphaltic oils. He further says coal is not 

 a bitumen because it is not soluble to any extent in the usual 

 solvents for bitumen, nor does it melt at comparatively low 

 temperatures, nor dissolve in heavy asphaltic oils. But on dis- 

 tillation it gives rise to products that are similar to natural 

 bicumens, and are therefore termed pyro-bitumens. We mav 

 therefore look upon bitumen as that portion of asphalt, wherever 

 found, soluble in carborr bi-sulphide, and asphalt as the mixture 

 of a certain type of petroleum bitumen with varying amounts of 

 mineral matter. The latter may be as high as 90 per cent, or 

 more, as in a sheet asphalt pavement; or as low as 01 per cent., 

 as m the residual pitches derived from the asphaltic petroleums. 

 It is in this sense that the term is used in this paper, further 



