ity of goods being treated is placed
in the chamber and allowed to burn itself out; the quantity used being
about 6 to 8 per cent. of the weight of the goods. After the
sulphuring the goods are simply rinsed in water and dried.

Sulphur bleaching is not an effective process, the colouring matter is
not actually destroyed, having only entered into a chemical
combination with the sulphur dioxide to form a colourless compound,
and it only requires that the wool be treated with some material which
will destroy this combination to bring the colour back again in all
its original strength; washing in weak alkalies or in soap and water
will do this. Another defect of the process lies in sulphur being
volatilised in the free form, and settling upon the wool causes it to
turn yellow, and this yellow colour cannot be got rid of.

The goods must be thoroughly rinsed with water after the bleaching,
the object being to rid the wool of traces of sulphuric acid, which it
often contains, and which if left in would in time cause the
disintegration of the wool.

Sometimes the wool is washed in a little weak ammonia or soda (p. 033)
liquor, but this is not advisable, as there is too much tendency for
the colour of the wool to come back again, owing to the neutralising
of the sulphur dioxide by the alkali.

Instead of using the gas, the sulphur dioxide may be applied in the
form of a solution in water. The goods are then simply steeped for
some hours in a solution of the gas in water until they are bleached,
then they are rinsed in water and dried. In this method it is
important that the solution of the gas be freshly made, otherwise it
is liable to contain but little sulphurous acid, and plenty of
sulphuric acid which has no bleaching properties, but, on the other
hand, is liable to lead to damage of the goods if it be not washed out
afterwards.

A better method of utilising the bleaching action of sulphur in a
liquid form is to prepare a bath of bisulphite of soda, and acidify it
with hydrochloric acid, then to enter the wool, stirring well for some
time, and allowing it to steep for some hours, next to expose to the
air for a while, and rinse as before.

It is better to allow the wool to steep for about an hour in a simple
bath of bisulphite, then enter into a weak hydrochloric acid bath for
a few hours. The acid liberates sulphur dioxide in a nascent
condition, which then exerts a more powerful bleaching action than if
it w