one hand, and
that of the dye-stuff on the other. Wool must be treated differently
from cotton, a process of dyeing which gives good results with the
latter fibre would lead to nothing but disastrous effects with wool or
silk; on the other hand, processes are used in the dyeing of wool
which could not be possibly used for cotton on account of the very
different properties of the fibre.

A few words as to the properties of wool as far as they relate to the
methods of dyeing may be of use. Wool has the property of resisting
the action of acids in a great degree, so that it may be treated with
even strong acids with impunity. On the other hand, alkalies and
alkaline solutions have strong action on it; the caustic alkalies
rapidly dissolve wool, and their use must be avoided in all cases of
dyeing this fibre. The carbonates of the alkalies have not so strong
an action, and therefore may be used in moderation; nevertheless, (p. 060)
too strong solutions of these should not be used. Soap has no
disintegrating action on wool, and soap solutions may be used whenever
necessary for cleansing or dyeing wool. Ammonia has no action on wool,
and it may be used in place of soap if desired. There is one feature
of wool that must be alluded to here, and that is its felting
property. When wool is boiled with water and is handled a good deal,
the fibres clot or felt together into a firm coherent mass. This
should be avoided as much as possible, and when wool is cleansed and
dyed in the loose condition it is absolutely necessary that every care
be taken to avoid felting. This condition is much influenced by the
temperature and the condition of the bath in which the wool is being
treated, too high a temperature or too prolonged a treatment tends to
increase the felting, therefore in dyeing wool prolonged treatment at
the boil must be avoided.

Further, the condition of the bath has some influence on this point;
it is found that an alkaline bath tends to considerably increase the
felting properties of the wool, and on this account dyers invariably
avoid the use of both the caustic and carbonated alkalies. Strong soap
liquors have also some influence in the direction of increasing the
felting, therefore soap should not be used if it can possibly be done
without. Ammonia has not so strong a felting action as the other
alkalies. Acids, on the other hand, exert a retarding action on the
felting of the wool, and this is a matter of some intere