The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

Coloring Finishing And Painting Wood

Before the war opened in 1914 the United States had imported not far from 350 different dyes from Germany. While at first some of the dyes of American manufacture were fugitive, because of the Jack of proper raw materials, and the inexperience of our chemists and workmen in quantity production, the quality soon improved, until at present American dyes rank well with those produced abroad.

It is of interest to note that, altho a very large number of foreign dyes are still imported, the volume is small, being only about 5 per cent, while 95 per cent of the total tonnage used is now manufactured by our own dye-factories here in the United States.

94. Products of Coal-Tar Distillation.—During the year 1845 Hofmann, a German chemist, discovered that the hydrocarbon, benzene, is present in coal-tar. Research students, especially the Englishman, Perkin, discovered Mauveine or Mauve somewhat accidentally when working with aniline, a derivative of benzene; and they found out that a beautiful violet or mauve color of tinctorial power is produced by the oxidation of aniline. Benzene (C6H6) is simply one of many coal-tar derivatives, as is also aniline which comes from nitrobenzene.

The various component parts of coal-tar are separated by distillation at various temperatures. The most important groups are indicated as follows:

1. Temperature up to 110° C. produce first runnings.
2. Temperature from 110° up to 210°C. distil out light and middle oils. From the above two groups at temperatures under 150cC. benzene (C6H6), toluene (C7H8), xylene (C8H10), and their many derivatives are obtained. The boiling-point of benzene is 81°C. Toluene boils at 110°C, and xylene at about 130° to 141°C. Aniline comes from benzene thru its derivative, nitrobenzene. This so-called naphtha, or light-oil distillate, represents commonly only about 3 per cent of the coal-tar weight, and the yield of benzene is about 11/2 per cent of the original tar.
3. Temperatures between 210° and 240°C. produce the heavy oils, known as the carbolic oils. In this group are found cresol, and especially phenol, and naphthalene (C10H8).
4. Temperatures from 240° up to 270°C. distil heavy or creosote oils. Much naphthalene is produced in the lower temperatures of this group, but little is present near the 270°C. temperature. Many hydrocarbons are mixed with coal-tar creosote oil, some of them being phenol, naphthalene, and anthracene, the lastnamed substance coming off at the highest temperatures, especially.

Coal-tar creosote is practically free from the light oils, which come off at the lowest temperatures, and "pitch" which remains as a residue at the temperature of 270°C. This creosote is similar in its properties to wood-tar creosote, and is used as a preservative. The creosote distillate represents about 10 per cent of the coal-tar weight, and may yield as much as about 8 per cent of naphthalene.