wer of
attracting excess of colour in any subsequent dyeing process and thus
lead to stains, the origin of which may not be readily grasped at the
first sight.

It is best, therefore, either to allow the solution to settle in the
cistern till quite clear, which is the simplest way, or to filter
through cloth.

The chemicing is best done cold and with weak solution, at 1/2 deg. Tw.
rather than 1 deg. Tw. Warming the liquor increases the rapidity of the
bleaching action, but there is a risk of over-chloring, which must be
avoided as far as possible, because there is then danger of tendering
the fibre, moreover, such over-chlored cloth has an affinity for
colouring matters that is not at all desirable, as it leads to the
production of stains and patches in the dyeing operations. It is much
better, when a single chemicing does not bleach the cloth sufficiently
and give a white, to run the cloth twice through a weak liquor rather
than once through a strong liquor.

Although the chemicing is followed by a sour, which, acting on the
bleaching powder, liberates chlorine that bleaches the fabric, yet the
greatest proportion of the bleaching effect is brought about while the
pieces are being piled up into heaps between the chemicing and the sour.
In this state they should be left for some hours, covered over with a
damp sheet, care being taken that they are not left piled so long as to
become dry, as in this event there is a great risk of tendering the
cloth or fabric; it is, therefore, a good plan to moisten them with a
little water from time to time. They should not be tightly piled up, but
be as loose as possible, so that the air can get to them, as it is the
carbonic acid and other acid vapours in the air, that by acting on the
chemic causes slow liberation of chlorine, which effects the bleaching
of the goods.

(10) =White Sour.=--After the chemicing the goods are treated to a sour,
for which purpose either hydrochloric acid or sulphuric acid may be
used.

Hydrochloric acid possesses the advantage of forming a more soluble salt
of lime (calcium chloride) than does sulphuric acid (calcium sulphate),
and it has a more solvent action upon any traces of iron and other
metallic oxide stains which may be present in the goods. On the other
hand, on account of its fuming properties, it is unpleasant to work
with. The souring is done by passing the goods through an acid liquor at
2 deg. Tw. strong and piling for two or three h