ce is of no importance in white goods. If, on the other hand,
the cotton has to be subsequently dyed with direct cotton colours (see
DYEING), the presence of oxycellulose may result in uneven dyeing.
Tendering of the pieces, due to insufficient washing after the final
souring operation, is a common defect in bleached goods. As a rule the
free acid can be detected by extracting the tendered material with
distilled water and adding to the extract a drop of methyl orange
solution, when the latter will turn pink if free acid be present.
Other defects which may occur in bleached goods are iron stains,
mineral oil stains, and defects due to the addition of paraffin wax in
the size.

_Bleaching of Linen._

The bleaching of linen is a much more complicated and tedious process
than the bleaching of cotton. This is due in part to the fact that in
linen the impurities amount to 20% or more of the weight of the fibre,
whereas in cotton they do not usually exceed 5%. Furthermore these
impurities, which include colouring matter, intracellular substances and
a peculiar wax known as "flax wax," are more difficult to attack than
those which are present in cotton, and the difficulty is still further
enhanced in the case of piece goods owing to their dense or impervious
character.

Till towards the end of the 18th century the bleaching of linen both in
the north of Ireland and in Scotland was accomplished by bowking in
cows' dung and souring with sour milk, the pieces being exposed to light
on the grass between these operations for prolonged periods.
Subsequently potash and later on soda was substituted for the cows'
dung, while sour milk was replaced by sulphuric acid. This "natural
bleach" is still in use in Holland, a higher price being paid for linen
bleached in this way than for the same material bleached with the aid of
bleaching powder. In the year 1744 Dr. James Ferguson of Belfast
received a premium of L300 from the Irish Linen Board for the
application of lime in the bleaching of linen. Notwithstanding this
reward, the use of lime in the bleaching of linen was for a long time
afterwards forbidden in Ireland under statutory penalties, and so late
as 1815 Mr Barklie, a respectable linen bleacher of Linen Vale, near
Keady, was "prosecuted for using lime in the whitening of linens in his
bleachyard."

[Illustration: FIG. 8.--Mather & Platt's Horizontal Drying Machine.]

The methods at present employed for