BLEACHING. 
merce rendered more active by having 
been mixed with one third of lime. After 
sufficient boiling it is washed with water', 
and put into close wooden troughs, con- 
taining the oxygenated acid, in which it is 
allowed to macerate for 3 or 4 hours, press- 
ing the cloth frequently, and exposing its 
surfaces to the action of the liquor. It is 
thus alternately exposed to the action of 
the alkaline ley and the oxygenated acid, 
till its colouring matter is completely ex- 
tracted, or it is sufficiently bleached, which 
requires in general from 4 to 8 immersions, 
according to the nature and coarseness of 
the cloth, cotton requiring fewer immer- 
sions in the bleaching liquor than linen. 
The subsequent steps of the process are to 
rub the cloth strongly with soft soap in 
■warm water. This renders the surface 
more smooth aud uniform, and takes away 
the smell of the oxygenated acid, which 
otherwise remains a considerable time. 
The cloth is again washed, and is lastly 
immersed for a short time in water, in 
which, from a one-sixtieth to a one-hun- 
dreth part of sulphuric acid has been dis- 
solved. The cloth thus acquires a much 
finer whiteness, from the sulphuric acid 
dissolving the remaining colouring matter 
which has resisted the action of the alkali 
and oxygenated acid, as well as a small 
quantity of iron and calcareous earth con- 
tained in all vegetable matter, or even de- 
posited in the cloth from the alkaline leys. 
Lastly, the cloth is generally exposed to 
the air for some days, and watered, to carry 
off any remains of either of the acids, and 
to remove completely the odour of the oxy- 
genated acid. 'Jhe theory of the action 
ot tiie oxygenated muriatic acid in bleach- 
ing is very simple, as stated by Berthollet. 
Its analogy to the common process by ex- 
posure to the air aud light, he observes, is 
complete. The end obtained by either 
is the combination of oxygen with the 
colouring matter of the vegetable. By 
this combination the colour is nearly de- 
stroyed, and the matter on which it de- 
pends is at the same time rendered soluble 
in the alkaline solution. Hence the neces- 
sity of the alternate application of these 
two chemical agents ; the one removing 
from the cloth what the other has rendered 
soluble, and which, although whitened, 
would regain part at least of its colour in 
time. Hence it is found, that the oxyge- 
nated muriatic acid is in this operation 
converted into common muriatic acid, and 
the alkaline solution is at length so loaded 
with colouring matter, that it becomes un. 
fit to be used. The only difference be- 
tween the two methods is, that in the one 
the oxygen is presented in a much more 
concentrated state than in the other, which 
facilitates the process, or renders it more 
rapid without injuring the strength of the 
fibre. At least, the only injury of this kind 
that can happen must arise from improper 
management; having used too strong an 
acid, or the not washing the cloth suffi- 
ciently after the process is finished. The 
greatest difficulty attending the use of oxy- 
muriatic acid arose from its suffocating 
odour, which rendered it almost impossible 
to work with it in an open vessel, and any 
apparatus contrived to turn the cloth and 
expose fresh surfaces of it to the action of 
the liquid in close vessels has been found 
imperfect. The addition of an alkali to 
the liquid removes in a great measure the 
odour of the acid, or at least prevents its 
unpleasant effects; and although it at the 
same time diminishes to a certain extent 
its bleaching power, this is more than com- 
pensated for by the advantage. The quan- 
tity of alkali added amounts to about 1 lb. 
ot the potash or pearlash of commerce to 
the quantity of acid prepared from 4 lbs. 
of muriate of soda. And to avoid the effer- 
vescence which would arise from the dis- 
engagement of the carbonic acid, during 
the combination of the oxymuriatic acid, 
tlie potash is deprived of it by the pre- 
vious addition of lime, the alkaline solu- 
tion after its operation being poured off 
clear. 
Independently of the weakening of the 
power of the acid by this addition, a con- 
siderable expense was introduced by the 
use of the alkali ; and it becaifie an object 
ot importance to the manufacturers of tins 
country to substitute a cheaper substance 
which should have the same effect. Lime 
was tried at first in an imperfect manner, 
but at length with such improvements that 
it is now always used. The difficulty of 
using it arose from the insolubility of the 
lime in water, the quantity taken up being 
so inconsiderable, that the solution could 
have little effect in correcting the odour of 
the acid. A very important improvement, 
therefore, was that of using lime suspended 
in water, and kept in suspension by an agi- 
tation in a close vessel, into which the gas 
was transmitted. Its condensation was 
thus facilitated, and the compound which 
is formed with the lime being soluble in wa- 
ter, the undissolved or unsaturated lime was 
