t air, by means of a specially designed self-contained
jacketed crutcher, in which two shafts carrying small blades or paddles
rotate in opposite directions, to reduce the density of the soap below
that of water and so enable the compressed tablet to float. The
difference in weight of a tablet of the same size before and after
aerating amounts to 10 per cent.

Ordinary milling soap is used as a basis for this soap; the settled soap
direct from the copper at 170 deg. F. (77 deg. C.) is carefully neutralised with
bicarbonate of sodium, oleic or stearic acids, or boro-glyceride,
perfumed and aerated.

Floating soap, which is usually white (some are of a cream tint), cannot
be recommended as economical, whilst its deficiency in lathering
properties, owing to occluded air, is a serious drawback to its
popularity as a toilet detergent.

_Shaving Soaps._--The first essential of a shaving soap, apart from its
freedom from caustic alkali or any substance exerting an irritating
effect upon the skin, is the quick production of a profuse creamy lather
which is lasting. Gum tragacanth is used in some cases to give lasting
power or durability, but is not necessary, as this property is readily
attained by the use of a suitable proportion of potash soap. The best
shaving soaps are mixtures of various proportions of neutral soda and
potash soaps, produced by the combination of ordinary milling base with
a white potash soap, either melted or milled together. Glycerine is
sometimes added, and is more satisfactorily milled in.

Every precaution should be taken to ensure thorough saponification of
the soaps intended for blending in shaving soap, otherwise there will be
a tendency to become discoloured and develop rancidity with age. Shaving
soaps are delicately perfumed, and are placed on the market either in
the form of sticks which are cut from the bar of soap as it leaves the
compressor, or stamped in flat cakes.

Shaving creams and pastes are of the same nature as shaving soaps, but
usually contain a larger proportion of superfatting material and
considerably more water.

TEXTILE SOAPS.

In the woollen, cloth, and silk textile industries, the use of soap for
detergent and emulsifying purposes is necessary in several of the
processes, and the following is a brief description of the kinds of soap
successfully employed in the various stages.

1. _Woollen Industry._--The scouring of wool is the most important
operation--it is th