What Every Member of the Trade Community Should Know about: Classification of Sets Under Htsus

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 edition. Excerpt: ...into two general classes, coal tar and water-gas tar. The specifications call for one or the other. They can be readily distinguished by the amount of freecarbon content. This is determined by dissolving the tar in carbon disulphide (CS2), the insoluble residue being carbon. Coal tar carries more free carbon than water-gas tar. 4. The volatile matter is determined not by an evaporation test as with asphalt, but by fractional distillation, the total per cent. distilled up to 1700 C, 2350 C, 2700 C, and 3000 C, respectively, being determined. This necessitates 4 weighings, but only one complete test is made. 5. Melting point test. From the residue remaining after the above distillation, 2 cubes, 1 c.c. each, are made, cooled to a given temperature, and suspended by a wire in water 1 inch above the bottom of a glass beaker. Heat is applied at a given rate to warm the water 50 C. per minute. The temperature at which the tar softens enough to touch the bottom of the beaker is taken. The result is the average of two determinations. Asphaltic oils.--These oils are used in maintenance work. The tests made are the same as for asphalt, except that in place of the penetration test, a viscosity test is applied. This is determined by the time taken for a specified quantity (50 c.c.) at a given temperature to flow through a small hole of specified size in the testing machine. The shorter the time, the more liquid the oil. Finished pavement.--The above tests all relate to the raw materials. It is important, however, that they be used in the proportions demanded by the specifications. To insure this, blocks of the freshly laid pavement are cut out and forwarded to the laboratory. The sample is first listed and numbered for future reference. A portion is...