One case of carbonic oxide poisoning in coal-tar distillation is described.[5] In cleaning out pitch from a still fourteen days after the last distillation a workman succumbed to carbonic oxide poisoning. This is at all events a rare eventuality, since no other case is to be found in the literature of the subject, but it is a proof that in the last stage of coal-tar distillation carbonic oxide plays a part.
Mention must be made of the frequent occurrence of severe skin affections in anthracene workers; they take the form of an eruption on the hands, arms, feet, knees, &c., and sometimes develop into cancer.
Observations in a chemical factory since 1892 showed that of thirty thus affected in the course of ten years twenty-two came into contact with paraffin.
Artificial Organic Dye Stuffs (Coal-tar Colours)
Manufacture.—The starting-points for the preparation of artificial coal-tar dyes are mainly those aromatic compounds (hydrocarbons) described in the preceding section. Besides these, however, there are the derivatives of the fatty series such as methyl alcohol (wood spirit), ethyl alcohol, phosgene, and, latterly, formaldehyde.
The hydrocarbons of the benzene series from tar distillation are delivered almost pure to the colour factory. Of these benzene, toluene, xylene, naphthalene, anthracene, and the phenols, cresols, &c., have to be considered.
Further treatment is as follows:
1. Nitration, i.e. introduction of a nitro-group by means of nitric acid.
2. Reduction of the nitrated products to amines.
3. Sulphonation, i.e. conversion to sulphonic acids by means of concentrated sulphuric acid.