soap-pan

In order to economise tank space, it is the general practice to store strong caustic lye (60° to 70° Tw., 33° to 37° B.) and to dilute it as it is being added to the soap-pan by the simultaneous addition of water.

The Handbook of Soap Manufacture H. A. Appleton

The charging hopper can be connected with the soap-pan by a pipe, and when the hopper is filled with liquid soap the plugs _c_ are raised and the air in the box C exhausted, thus causing the soap to descend into the cooling tubes.

The Handbook of Soap Manufacture H. A. Appleton

The molten settled fatty materials _en route_ to the soap-pan should be passed through sieves sufficiently fine to free them from suspended matter.

The Handbook of Soap Manufacture H. A. Appleton

Prolonged agitation with air has a tendency to oxidise the oil, which increases its specific gravity and refractive index, and will be found in the soap-pan to produce a reddish soap.

The Handbook of Soap Manufacture H. A. Appleton

The rosin may be added to the soap-pan after a previous partial saponification with soda ash, and removal of colouring matter, and finally saponified with caustic soda lye, or, as is more generally adopted, as a rosin change.

The Handbook of Soap Manufacture H. A. Appleton

Geitel and Lewkowitsch, who have studied this question from the physical and chemical point of view respectively, are of opinion that when an oil or fat is saponified, these three reactions do actually occur side by side, the soap-pan containing at the same time unsaponified triglyceride, diglyceride, monoglyceride, glycerol and soap.

The Handbook of Soap Manufacture H. A. Appleton

_Bone fat_ often contains calcium (lime) salts, which are very objectionable substances in a soap-pan.

The Handbook of Soap Manufacture H. A. Appleton

_ -- The melted fats and oils are introduced into the soap-pan and boiled by means of open steam with a caustic soda lye 14° to 23. 5° Tw. (10° to 15° B.).

The Handbook of Soap Manufacture H. A. Appleton

Having described the most important and interesting oils and fats used or suggested for use in the manufacture of soap, let us now consider briefly the methods of bleaching and treating the raw materials, prior to their transference to the soap-pan.

The Handbook of Soap Manufacture H. A. Appleton

In this case a system is generally adopted; for example, soap of the best quality is made in a clean pan, the nigre remaining is worked up with fresh material for soap of the next quality, the nigre from that boil, in its turn, is admixed with a charge to produce a batch of third quality, and the deposited nigre from this is again used for a fourth quality soap -- the nigre obtained from this latter boil would probably be transferred into the cheapened "washer" or perhaps if it was dark in colour into the brown soap-pan.

The Handbook of Soap Manufacture H. A. Appleton