and yarn
these three operations are sufficient, but for piece goods a larger
number of operations is usually necessary in order to obtain a
satisfactory result.

_Loose Cotton._--The bleaching of loose or raw cotton previous to
spinning is only carried out to a very limited extent, and consists
essentially in first steeping the material in a warm solution of soda
for some hours, after which it is washed and treated with a solution
of bleaching powder or sodium hypochlorite. It is then again washed,
soured with weak sulphuric or hydrochloric acid, and ultimately washed
free from acid. Careful treatment is necessary in order to avoid any
undue matting of the fibres, while any drastic treatment, such as
heating with caustic soda and soap, as used for other cotton
materials, cannot be employed, since the natural wax would thereby be
removed, and this would detract from the spinning qualities of the
fibre. In case the cotton is not intended to be spun, but is to serve
for cotton wool or for the manufacture of gun cotton, more drastic
treatment can be employed, and is, in fact, desirable. Thus, cotton
waste is first extracted with petroleum spirit or some other suitable
solvent, in order to remove any mineral oil or grease which may be
present. It is then boiled with dilute caustic soda and resin soap,
washed, bleached white with bleaching-powder, washed, soured and
finally washed free from acid. In these operations, a certain amount
of matting is unavoidable, and it is consequently necessary to open
out the material after drying, in scutchers.

_Cotton Yarn._--Cotton yarn is bleached in the form of cops, hanks or
warps. In principle the processes employed are the same in each case,
but the machinery necessarily differs. Most yarn is bleached in the
hank, and it will suffice to give an account of this process only. The
sequence of operations is the same as in the bleaching of cotton
waste, and these can be conducted for small lots in an ordinary
rectangular wooden vat as used in dyeing, in which the yarn is
suspended in the liquor from poles which rest with their ends on the
two longer sides of the vat. For bleaching yarn in bulk, however, this
mode of procedure would involve so much manual labour that the process
would become too expensive. It is, therefore, mainly with the object
of economy that machinery has been introduced, by means of which large
quan