Page:Popular Science Monthly Volume 81.djvu/35

Rh The emulsified water can be removed from the crude Trinidad asphalt by grinding it to a fine powder and exposure to the air, or by heating the material to a temperature above the boiling point of water, and until the bitumen melts. Upon the latter fact is based the process of refining which is used industrially, and which will be described later.

The bitumen of Trinidad asphalt can be separated from the mineral matter by solvents, and thus prepared is a brilliant, glossy, pitchlike substance, which has a semi-conchoidal fracture when struck a sharp blow, but which yields to gentle pressure and slowly flows at summer temperatures. It softens at 76° C, flows quickly at 83° C, but is not liquid until a temperature is reached which is above 100° C. It has a specific gravity, when entirely free from mineral matter, of 1.032 at 25° C.

Its ultimate composition is

It is noticeable that this bitumen is characterized by the large percentage of sulphur which it contains, by the presence of nitrogen, and by the absence of oxygen.

It is to the sulphur which is present, as will be shown later on, that the valuable properties of the Trinidad bitumen are to be attributed.