226 
more than drawing or combing the flax in 
small parcels at a time, through a pile or 
group of polished and sharp iron spikes, 
placed (irmly in woo l through an iron plate. 
The spikes are placed pretty close together: 
the first hackle (for deferent hackles must 
be used) is coarse, the second finer, and the 
third finer still. 
Tiie process of hackling answers a double 
or triple purpose ; first, it divides the fibres 
of the llax, as much as this can be effected 
by mechanical means ; secondly, it separates 
the minute fragments of wood which escaped 
the process of scutching ; and lastly, it se- 
parates the short coarse flax, commonly 
called town 
Spinning and weaving are too well known 
to need description. The linen, as it comes 
from the loom, is charged with what they 
call the weaver’s dressing, which is a paste of 
ilour boiled in water; and as this is brushed 
into the yarn of the warp before it is woven, 
it is somewhat difficult to separate it w hen 
dry. To discharge this paste, the linen must 
lie steeped in water for about forty-eight 
hours; when this extraneous substance under- 
goes a kind of fermentation, which does not 
extend to the substance of the linen itself, 
upon the same principle that the green sap 
is disengaged from the flax without injury to 
its texture. 
When the linen is well washed after this 
last process, it contains nothing that water ; j 
can separate ; it is of a greyish white colour, 
although the fibres of which it is composed, 
when divested of every adventitious sub- 
stance, are naturally very white. 
The matter which thus colours the linen, 
is of a resinous nature, insoluble in water, 
and from its intimate union or dissemination 
through the very fibres of the flax, is difficult 
of separation, even by those substances 
which have a solvent power oyer it. 
To disengage it, however, in as cheap and 
expeditious a manner as possible, without in- 
juring the texture of tine fabric, is the sole 
object of the process of bleaching. 
Potash is the first menstruum which should 
be used in bleaching. It is most economical 
to render it caustic, for the purpose of bleach- 
ing. This is done by adding quicklime to. 
the mild potash, the former having a stronger 
affinity for the carbonic acid than the latter. 
But care must be. taken not to use the alkali 
too strong, otherwise it will attack and de- 
stroy the ribro.us part. The potash, from 
its ^solvent power over the colouring matter, 
dissolves and separates the part immediately 
exposed to its action; that is, the pad of it 
which rests superficially upon the fibres ot 
the flax or thread ; for it requires ten or 
twelve repeated boilings, at least, with the 
alternate agency of the atmosphere, to sepa- 
rate the whole of the resin. 
It might be asked, why such an active 
solvent as potash should not carry away the 
whole of the resin at once, or at least as much 
as it alone could in any waysepaiate. inis 
requires an explanation. A tiat appears 
to us to be a single ultimate fibre of flax in 
grey linen, is composed ot a bundle ot mi- 
nute filaments, closely cemented or aggluti- 
nated . together by the resinous matter; the 
potash first used therefore acts only upon the 
resin of the external costing of filaments; 
by which means they are loosened or sepa- 
rated, and exposed to the further action, of 
BLEACHING. 
the air. The second boiling in potash opens 
a second layer, and thus, successively, layer 
after layer ; until the whole is divided, oi 
opened to the centre. Were the solution ot 
potash sufficiently strong to force its way 
at once to the centre, it would act upon the 
filaments themselves, and destroy the texture 
of the doth. 
Each filament, after the process of potash, 
retains an impregnation of colouring matter, 
so intimately united, as to resist the further 
action of it. This can only be removed oy 
the slow and gradual influence of the oxygen 
gas of the atmosphere. 
From the properties of oxygen gas and 
potash, their manner of operating is very ob- 
vious. The oxygen gas dissolves in each 
boiling a certain quantity oi the. colouring 
matter, with which it forms carbonic acid gas, 
and partly divides the filaments that eluded 
the action of potash. T he carbonic acid gas, 
from its volatility, flies oft and mixes with tne 
atmosphere. Thus, alternately, the one 
dissolving, and the other burning out (toi 
bleaching is slow combustion), the linen is 
whitened. 
Mankind have at all times employed tree 
air as the most convenient menstruum toi 
bleaching. When tired with the slowness of 
its action, they assisted it by detersive leys, 
which abridged the process a little : and this 
union of boiling and exposure on the gra^s, 
formed the whole of the antient art ot bleach- 
ing. Formerly, when it was necessaiy to 
bleach cloth, it was customary to immerse it 
in pure water, to free it from the dressing. 
Thus preliminary operation was sometimes 
hastened by a cold ley ; the cloth was then 
rinsed in running water, and spread out on 
a meadow, round which ran a stream ot lim- 
pid water that served for watering the different 
pieces. 
After being exposed in this mannei some 
time, the cloth was washed and bolted in a 
fresh ley ; it was then again spread out on 
the grass: and this operation was several 
times repeated until the- required whiteness 
was obtained. It was still necessaiy to wind 
it through soapy water, not only to give it 
softness and pliability, but to bleach com- 
pletely the borders, which oppose the longest 
resistance. 
It was brought to its ultimate state ot white- 
ness by drawing it through whey, or diluted 
sulphuric acid. By this short description it 
may be seen, that a considerable time was 
necessary before the absorption of oxygen 
could take place ; to hasten this operation 
of nature appeared impossible, until modern 
chemistry had demonstrated that oxygen 
might be extracted, and combined with water, 
to be afterwards applied to substances whcie 
its influence might be necessary. 
To promote the speedy action ot atmo- 
spheric air, or rather the oxygenous part of 
it, in its ordinary elastic state, is well known 
to be impossible. . • 
The ox: genated muriatic acid gas lias 
been already described under the word Air. 
This gas, combined with water, forms the 
oxygenated muriatic acid, which is therefore 
only 'a combination ot muriatic acid and oxy- 
gen; but this principle adheres but weakly 
to the muriatic acid. 
All vegetable colours are attacked by this 
acid antf whitened with more or less celerity, 
which depends on their greater or less facility 
of combinin g with oxygen. The colon ring.™ a t- 
ter undergoes a real slow combustion, v- .rich 
terminates by the formation of carbonic a< id, 
which escaping under the form of elastic fluid, 
produces what we call bleaching. 
In whatever manner the oxygenated muri- 
atic acid is procured, it is evident that the 
oxygen adheres to it only weakly ; and it is 
oil this property that the possibility depends 
of producing speedily, in manufactories, that 
action which the atmosphere produces but 
slowly, and of bleaching in a space of time 
proportionally short. 
The oxygenated muriatic acid is employed 
in four different ways for the purposes of 
bleaching ; first, in the state of gas alone ; 
secondly, in the state of gas combined with 
water, or what is called tire acid; thirdly, 
potash is mixed with the acid to condense tne 
gaseous vapour and destroy its suffocating 
odour ; fourthly, oxygenated muriates, dis- 
solved in water, are employed. 
The first method, viz. employing the gas, 
was never used but for the purpose of experi- 
ment ; as the vapour is of so noxious a quality, 
that to breathe it is fatal, and several people 
fell a sacrifice to their attempts in employing 
it. _ . 
When condensed in water, or in the state 
of oxygenated muriatic acid, it was found in- 
convenient in the large way, on account of 
the expence and difficulty in constructing 
the necessary apparatus, and the suffocating 
vapour which escaped. 
For the discovery of the oxygenated muri- 
atic acid, its effects on colouring matter, and 
its inestimable advantages, the arts are in- 
debted to the justly celebrated Scheele. M. 
Bertliollet lost no time in applying this curious 
and highly interesting substance to the most 
important practical uses. His experiments 
of bleaching by oxygenated muriatic acid, 
proved completely successful, and he did not 
delay to communicate his valuable labours 
to the public. The new method of bleach- 
ing was quickly and successfully introduced 
into the manufactories of Manchester, Glas- 
gow, Rouen, Valenciennes, and Courtray ; 
and it has since been gradually adopted in 
almost all parts of Great Britain, Ireland, 
France, and Germany. The advantages 
that result from this method, which accele- 
rates the process of whitening cottons, linens, 
paper, &c. to a surprising . degree, in every 
season of the year, can be justly appreciated 
by commercial people only, who experience 
its beneficial effects in many ways, but par- 
ticularly in the quick circulation of their capi- 
tals. 
To save the expence of first preparing the 
muriatic acid, the usual practice is to mix 
with the oxide of manganese, muriate of soda 
or common salt, arid sulphuric acid diluted 
with water. I he sulphuric acid acts upon 
the salt, and disengages from it the muriatic 
acid, which is oxygenated by the oxyde of 
manganese. 1 he proportions observed when, 
cotton is to be bleached, are. 
Manganese - 30 parts. 
Common salt, 80 
Sulphuric acid, 60 
Water, - WO. 
For linen-cloth the proportions are a9 
follow : 
Manganese, - 60 parts,: 
