CARBONISING WOOL RAGS

The " wet " or dilute sulphuric acid process is now almost entirely superseded for rags by the " dry " or hydrochloric acid gas treatment, because the colours of the rags do not " bleed " so much as with the wet process. The gas is generated in a retort placed beside the extracting chamber. In the retort is placed a mixture of common salt and sulphuric acid, or the gas is produced by merely heating liquid hydrochloric acid (spirits of salt). The extracting chamber consists of a revolving cylindrical cage, contained in a cased iron vessel heated by steam In this the rags are subjected to the acid fumes. The rags are slightly moistened by steam to facilitate the action of the acid on the cotton. The inside of the cylinder is covered with hooks, and, as it turns slowly, the rags are carried up and drop from the hooks, ensuring a thorough contact with the gas. The operation is complete in three hours. After the carbonising, the shoddy is put through a burr crushing machine, where the charred vegetable matter is removed. Then the goods are washed well or neutralised, and are then ready for the next process of manufacture.