Page:International Library of Technology, Volume 93.djvu/106

 EXAMINATION OF OILS

52. The color of the American crude petroleum varies from a clear water white, through a straw yellow, light amber, red, deep red, dark brown, to an opaque black.

The first, although only a freak in the petroleum fields, has been found in a well at Holders Run, Armstrong County, Pennsylvania. The others are of common occurrence, and may be seen in the crude oils of West Virginia, Pennsylvania, Ohio, Indiana, California, Kentucky, Texas, and Wyoming. Each of these states has produced crude oils of various shades, the light-colored oils usually coming from some strata nearer the surface than those of a darker shade.

53. Nearly all crude oils have a fluorescence varying from blue to dark green. That of Pennsylvania is of a beautiful light grass green. The specific gravity of crude oil varies from .77 to .98, all being lighter than water. It has been found that there exists a certain connection between color and specific gravity, the lighter-colored oils usually haying a lower specific gravity, and vice versa.

54. The variability mentioned in the preceding articles depends partly on the chemical composition and partly on the physical condition of the oil. All crude oils hold more or less natural gas in solution, which lowers their specific gravity; on the other hand, oils containing a comparatively large percentage of paraffin or asphalt have a greater specific gravity — this also applies to all sulphur oil. It further has been found that oils having low specific gravities furnish a greater percentage of gasolines and illuminating oils than those that are heavier.

The specific gravity of an oil plays an important part in its price. The more important factor in setting the price of oil, however, is its chemical composition and freedom from suspended matter. Heavy oils hold water and earthy matter in suspension, and must be heated in order that these may be settled before the oils are received by the pipe line. This causes a loss of the more volatile parts, and necessarily