Continuous tar acid distillation plant, c 1956.
© Science Museum / Science & Society Picture Library
Model (scale: unknown). From 1812, the the coal gas industry expanded rapidly with the result that large quantities of coal tar accumulated, which had no known use. In 1819, Macintosh discovered that the tar contained ammonia and naptha, which could respectively be used to make a dye and to disolve rubber in a proces for waterproofing cloth. It was not until 1846 that a full investigation of the constituents of coal tar was carried out by Mansfield, who was fatally burned during the work. From this, the coal tar distillation industry developed, producing a large range of chemicals with industrial uses, including benzene, napthalene and phenol. Complex plant was developed, such as this example which separates the components of the acid fraction of the tar.