which, in the example given, would be 1-1/2 cwt., may
be added to the solution prior to the addition of rosin or sprinkled in
towards the finish of the boiling. When the whole has been sufficiently
boiled and allowed to rest, the liquor containing the colouring matter
will float over the resinate, and, after removal, may be replaced by
another washing.

Many other methods have been suggested for the bleaching, refining and
treatment of materials intended for saponification, but the above
practical processes are successfully employed.

All fats and oils after being melted by the aid of steam must be allowed
to thoroughly settle, and the condensed water and impurities withdrawn
through a trap arrangement for collecting the fatty matter. The molten
settled fatty materials _en route_ to the soap-pan should be passed
through sieves sufficiently fine to free them from suspended matter.

CHAPTER V.

SOAP-MAKING.

_Classification of Soaps--Direct Combination of Fatty Acids
with Alkali--Cold Process Soaps--Saponification under Increased
or Diminished Pressure--Soft Soap--Marine Soap--Hydrated Soaps,
Smooth and Marbled--Pasting or Saponification--Graining
Out--Boiling on Strength--Fitting--Curd Soaps--Curd
Mottled--Blue and Grey Mottled Soaps--Milling Base--Yellow
Household Soaps--Resting of Pans and Settling of
Soap--Utilisation of Nigres--Transparent Soaps--Saponifying
Mineral Oil--Electrical Production of Soap._

Soaps are generally divided into two classes and designated "hard," and
"soft," the former being the soda salts, and the latter potash salts, of
the fatty acids contained in the material used.

According to their methods of manufacture, soaps may, however, be more
conveniently classified, thus:--

(A) Direct combination of fatty acids with alkali.

(B) Treatment of fat with definite amount of alkali and no separation of
waste lye.

(C) Treatment of fat with indefinite amount of alkali and no separation
of waste lye.

(D) Treatment of fat with indefinite amount of alkali and separation of
waste lye.

(A) _Direct Combination of Fatty Acids with Alkali._--This method
consists in the complete saturation of fatty acids with alkali, and
permits of the use of the deglycerised products mentioned in chapter
ii., section 2, and of carbonated alkalies or caustic soda or potash.
Fatty acids are readily saponified with caustic soda or caustic potash
of all stren