Sulphuring is generally performed in an 
arched or very close chamber, constructed 
in such a manner, that the articles to be ex- 
posed to the action of the sulphur can be sus- 
pended on poles. The chamber being tilled, 
a certain quantity of sulphur is put in a state 
of combustion in iiat dish.es, having a large 
surface with very little depth ; the entrance 
is speedily shut, and all the inte: slices around 
the door are carefully stopped to prevent 
the access of the atmospheric air. The acid 
generated by the combustion of the sulphur, 
penetrates the stuffs, attacks the colouring 
matter, destroys it, and effects the bleaching. 
The stuffs are left in the stoves some time after 
the deflagration has ceased. This time varies 
from six to twenty-four hours. They are then 
taken out, and made to pass through a slight 
washing with soap, to remove the roughness 
they have acquired by the action of the acid, 
and to give them the necessary softness. 
This process is imperfect. At first, the 
acid of the sulphur acts only on the surfaces, 
and does not penetrate. This aerial immer- 
sion is not sufficient ; the gas cannot intro- 
duce itself to a sufficient depth into the stuffs, 
and the superficies only are whitened. 
A superior method has been lately invent- 
ed, which is by making use of the sulphure- 
ous acid. 
The sulphureous acid, or that acid gene- 
rated by the imperfect combustion of sulphur, 
differs from the sulphuric acid (oil of vitriol), 
by its containing less of the acidifying prin- 
ciple, and by being the mean term between 
the sulphuric acid. 
Sulphureous .acid gas unites very easily 
with water, and in this combination it may 
be employed for bleaching wool and silk. 
The sulphureous acid in this state of liquidi- 
ty, may be prepared by making it traverse 
water in an apparatus nearly similar to that 
used fi r preparing oxygenated muriatic acid. 
'1 he most economical method of obtaining 
it, is to decompose sulphuric acid (oil of vi- 
triol), by the mixture of any combustible 
matter capable of taking from it a part of its 
oxygen. In exact experiments of the la- 
boratory, when the chemist is desirous of 
having great purity, it is obtained by means 
of metallic substances, and particularly by 
mercury ; but for the purpose of which we are 
treating, where great economy is required, 
we should recommend the most common sub- 
stances. We shall therefore give the follow- 
ing process. Take chopped straw, or saw- 
dust, and introduce it into a mattress; pour 
over it sulphuric acid, applying at the same 
time heat, and there will be disengaged sul- 
phureous acid gas (vapour of sulphur), 
which may be combined with water in the 
apparatus. 
I lie pieces are rolled upon the reels, and 
are drawn through the sulphureous acid by 
turning them, until it is observed that the 
v Idleness is sufficiently bright. They.are then 
taken out, and are left to drain on a bench co- 
vered with cloth, lest they should be stained 
inconsequence of the decomposition of the 
wood bv the sulphureous acid; they are next 
washed in river Water, and Spanish white is 
employed, if it should be judged necessary. 
J his operation is performed by passing the 
pieces through a tub of clear water, in which 
about eight pounds of Spanish white have 
been dissolved. To obtain a fine whiteness, 
the stuffs, in general, are twice sulphured. 
BLEACHING. 
According to this process, one immersion 
and reeling two or three hours are sufficient. 
Azuring or bluing is performed by throwing 
into the Spanish-white liquor, a solution of 
one part ot Prussian blue to 400 parts of 
water ; shaking the cloth in the liquid, and 
reeling it rapidly. The operation is termi- 
nated by a slight washing with soap, to give 
softness and pliability to the stuffs. The final 
operations of drying, stretching, pressing, &c. 
are foreign to our present subject. 
Bleaching of silk. Silk is a semitrans- 
parent matter, spun by a caterpillar, and 
formed ot a substance contained in its body, 
wlfich becomes hard in the air. .This insect 
inhabits warm climates, being indigenous 
in Asia : it was naturalized in Europe about 
the time ot the downfal ollhe Roman empire. 
I he filaments prepared bv the silkworm 
are rolled up in a cod or ball." In this state, 
in which we find it, it is covered with a yel- 
low varnish, which destroys its brilliancy "and 
renders it rough. Silk by chemical analysis 
gives carbonate o f ammonia and oil ; water 
at a boiling heat produces no effect upon it; 
alcohol makes it experience no change ; but 
concentrated alkaline leys attack and dissolve 
it. 
To give splendour to silk, it must be freed 
from its varnish. This covering is soluble 
in alkaline leys. . Silk is generally scoured 
by means of soap, by which it loses one-fourth 
its weight. The matter disengaged from 
it is very fetid, and if the silk is not rinsed in 
plenty of water, putrid fermentation will take 
place. Even when the best soap is used, it 
is generally suspected that it injures the white- 
ness of the silk. The splendour of the Chi- 
nese silk is brighter than that of the Euro- 
pean, and the Chinese employ no soap in 
their operations. A slightly alkaline lev' will 
dissolve the varnish of the silk without using 
soap, and this has also been effected by the 
action ot boiling water at a very high tempe- 
rature. J 1 
I he method which has been used success- 
fully in France is as follows : 
lake a solution of caustic soda, so weak as 
to mark only a fourth of a degree, at most, 
of the areometer for salts, and fill with it the 
boiler of the apparatus for bleaching with 
steam. Charge the frames with skeins of 
raw silk, and place them in the apparatus 
until it is full ; then close the door, and make 
the solution boil. Having continued the 
ebullition for twelve hours, slacken the fire, 
and open the door of the apparatus. The 
heat of the steam, which is always above 250°, 
vyili have been sufficient to free the silk from 
the gum, and to scour it. Wash the skeins 
in warm water ; and, having wrung them, 
place them again on the frames in the appa- 
ratus, to undergo a second boiling. Then 
wash them several times in water, and im- 
merse them in water somewhat soapy, to 
give them a little softness. 
Notwithstanding the whiteness which silk 
acquires by these different operations, it must 
be carried to a higher degree of splendour by 
exposing it to the action of sulphureous acid 
gas, in a close chamber, or by immersing it 
in sulphureous acid, as before recommended 
for w ool. 
Bleaching prints, and printed hooks. An 
application has been made ot the new mode 
of bleaching, to the whitening of books and 
prints that have beensoiledby smoke and time. 
229 
Simple immersion in oxygenated muriatic 
acid, letting the article remain in it a longer 
or shorter space of time according to the 
strength of the liquid, will be sufficient to 
whiten an engraving : if it is required to 
whiten the paper of a bound book, as it is 
necessary that all the leaves should be moist- 
ened by the acid, care must be taken to open 
the book well, and to make the boards rest on 
the edge of the vessel, in such a manner that 
the paper alone shall be dipped in the li- 
quid: the leaves must be separated from 
each other, in order that they may be equallv 
moistened on both sides. 
The liquor assumes a yellow tint, and the 
paper becomes white in the same proportion; 
at the end ot two or three hours, the book 
may be taken from the acid liquor, and 
plunged into pure water, with the same care 
and precaution as recommended in regard 
to the acid liquor, that the water may exactly 
touch the two surfaces of each leaf. The 
water must be renewed every hour, to ex- 
tract the acid remaining in the paper, and to 
dissipate the disagreeable smell. 
By following this process, there is some 
danger that the pages will hot be all equally 
whitened; either because the leaves have not 
been sufficiently separated, or because the 
liquid has had more action on the front mar- 
gins than on those near the binding. On this 
account, the best way is to destroy tiie bind- 
ing entirely, that each leaf may receive an 
equal and perfect immersion ; and this is the 
second process recommended by M. C'liap- 
tal. 
“ They begin,” says lie, “ by unsewing 
the book, and separating it into leaves, which, 
they place in cases formed in a leaden tub, 
with very thin slips of wood or glass, so that 
the leaves, when laid flat, are separated from 
each other by intervals scarcely sensible. 
I he acid is then poured in, making it fall on 
the sides of the tub, in order that the leaves 
may not be deranged by its motion. When 
the .workman judges, by the whiteness of the 
paper, that it has been sufficiently acted upon 
by the acid, it is drawn off by a cock at the 
bottom of the tub, and its place is supplied 
by clear fresh water, which weakens and car- 
ries off the remains of the acid, as well as the 
strong smell. The leaves are then to be 
dried, and alter being pressed, may be again 
bound up. 
“ I be leaves may be placed also vertically 
in the tub ; and this position seems to posse'ss 
some advantage, as they will be less liable 
to be torn. With this view 1 constructed a 
wooden frame, which I adjusted to the proper 
height, according to the size of the leaves 
which I wished to whiten. This frame sup- 
ported very thin slips of wood, leaving only 
the space of half a line between them. "I 
placed two leaves in each of these intervals, 
and kept them fixed in their place by two 
small wooden, wedges, which I pushed in 
between the slips. " When the paper was 
whitened I lifted up the frame with leaves, 
and plunged them in cold water, to remove 
the remains of the acid, as well as the smell ; 
this process I prefer to the other. 
“By this operation books are not only 
cleaned, but the paper acquires a degree of 
whiteness superior to what it possessed when 
first made. The use of this acid is attended 
also with the valuable advantage cf destin- 
ing ink-spots. r J his liquor has no action upon 
