Q. 3160. Decolorizing oils.

Manufacturer and Builder 2, 1883

Q. 3160. Decolorizing oils.
Please give me the best process known for decolorizing oils.
- P. H. T., Chicago, Ill.

Answer. This inquiry is not specific enough for us to answer intelligently. The methods adopted for decolorizing (bleaching) oils vary with the nature of the oil. Some oils cannot be succesfully bleached, a statement which is especially true of oils that have been burnt or charred by any previous process. The following are the several methods in use, and experiment alone in many cases can determine which is the best to employ in any peculiar case:
1st. Exposure to sunlight, in large white glasses, which soon bleaches the oil, but gives it a rancid flavor.
2d. Agitation with a.2 per cent solution of potassium permanganate. This agent bleaches effectively, but also leaves a bad flavor.
3d. Agitation with water containing gum, and addition to the emulsion formed, of coarsely crushed wood charcoal, warming the whole to nearly 212° Fah., and, when cold, dissolving out the oil by means of ether or petroleum spirit. The latter is recovered by distillation. The result is said to be good.
4th. Passing nitrous acid vapors through the oil.
5th. Clarifying by adding to 500 parts of oil 50 parts of China clay and 50 of water.
6th. Agitation of the oil at ordinary temperatures with a weak solution of albumen. Heat with steam to coagulate the albumen, allow the clots to settle, and remove the clarified oil by decantation.
Many oils are partially or completely discolored by filtration through or agitation with freshly burnt animal charcoal or bone-black. The filters used are similar to those employed in the sugar refineries.