Page:International Library of Technology, Volume 93.djvu/98

 called the still, these liquids may be boiled out one at a time, thus separating them, the vapors being collected in a special cooling apparatus, known as a condenser. This process of successive separation of the more volatile from the less volatile parts of a substance by vaporization is termed fractional distillation.

39. Order of Distillates.— The order of the distillates, as the products of distillation are called, is given in Table V.

TABLE V PRODUCTS OBTAINED FROM PETROLEUM Name Boiling Point Degrees Fahrenheit Specific Gravity Density Baumé's Scale Petroleum ether Gasoline C — petroleum — naphtha B— petroleum — naphtha A — petroleum — naphtha Illuminating oil (kerosene) Lubricating oil Paraffin or asphalt Coke 104 to 158 158 to 176 176 to 212 212 to 248 248 to 302 302 to 572 .65 to .66 .66 to .67 .67 to .707 .707 to .722 .722 to .737 .753 to .864 .864 to .96 85 to 80 80 to 78 78 to 68 68 to 64 64 to 60 56 to 32 32 to 15

The order shows how the products come over in the distilling apparatus. The first column of figures gives the highest and lowest boiling points of the various distillates. Two boiling points are given, since there are usually several hydrocarbons, each with a slightly different boiling point, mixed together in every oil put on the market. The specific gravity is the ratio of the weight of the oil to that of water. The last column is the measure of the specific gravity or density according to measurements by Baumé's hydrometer, an instrument according to which oils are usually rated in the markets. Table VI gives the specific gravities corresponding to the readings of the Baumé hydrometer.