BLEACHING. 
quality and texture of the ra£, it is then either to be pref- 
fed, or (land in tome convenient receptacle to drain away 
the fuperfluous water, and then put into the box or cafe 
prepared for bleaching the paper, or any other box, chert, 
or cafe, made of wood, of any lliape ov dimenfions, only 
obferving it is perfectly tight. 1 have ufed frequently, 
for this purpofe, cafes three feet fquare, and about two 
feet three inches deep. The noxious vapour which ilfued 
from the bleaching-cafes immediately on their being 
opened, having made (everal of the people employed 
therein extremely ill, and having experienced the perni¬ 
cious effects of it feverely myfelf, I turned my attention 
to a preventive; and, confidering the attraftions of all 
alkalies with acids, I difcovered, after trying various 
means, that the lixivium which we have always at hand 
anfwered the purpofe fully. When I have put it in too 
ftrong, or in too great a quantity, its effects have been 
curious : in feveral of thofe trials, after putting in my 
lixivium of various ftrengths and quantities, laying on my 
falfe bottom, and throwing in the article thereon, to the 
amount of at lead one hundred weight and a quarter in 
each cafe, I have found on opening, after (landing the 
ufual time of eight or ten hours, the cafe which had the 
weakeft portion of the lixivium well done throughout; 
where it was a little ftronger, one fmall fpot in the centre 
had the colour untouched ; and, w’here it was ftrongeft, 
one large globular form in the middle, of about eighteen 
inches diameter, was as full of colour as when put in; 
while all round, top, bottom, and fides, particularly the 
bottom, was purely white. This I attributed to the power¬ 
ful attraction of the lixivium, drawing the gaz down at 
the fides and corners, where it would find an eafier partage 
than in the centre, where it lay in a more folid body. One 
gallon of the fecond running of the lixivium will be gene¬ 
rally found a proper quantity for every hundred weight, 
to draw the bleaching power into the pulp, and render 
the procefs fafe and pleafant to the operator. It may be 
fuppofed much of the gaz muft be waited in the lixivium: 
if put in injudicioully it will, but, if in a proper quantity, 
the fame charge will bleach much more effectually than 
without it; being fo volatile that it is difficult to confine 
it. I have feen the finer and more fubtile parts penetrate 
through the neck of a (tone retort of confiderable thick- 
tiefs, which is foon rendered porous by repeated ufe ; and, 
as foon as the cafe was opened, great quantities would fly 
off, and, if the people employed did not fly from it for a 
time, they Would experience a trembling of the limbs, lick 
head-ach, painful fenfation at the rtomach and throat, and a 
wheefingcough, as if affliCled with a violent arthma; all of 
which are removed by the application of the lixivium. As 
the gaz decompofes all the fubftances found in the pores of 
w'ood, to thedeftruCfion of the wood and continual decreafe 
of the bleaching power, it will be neceflary to line the cafe 
with fome kind of cement that will repel it: I have lined my 
box or cafe with a thick coat of white paint, which hath an¬ 
fwered tolerably well. When I have thus prepared my box 
or cafe with the lixivium and falfe bottom, I fill it with the 
article to bleach ; having clofed the cover, I fix the retort 
with the chemical mixtures heretofore mentioned. The 
precife charge to each of thefe retorts cannot be affixed, 
but muft be regulated by the article to be bleached, which 
the judgment and ingenuity of the operator muft deter¬ 
mine ; for inftance, that charge which might with fafety 
be employed on a ftrong coarfe rag would injure the tex¬ 
ture of a fine or tender one; and that charge which would 
be fufficient for a fine rag would be ineffectual for a very 
coarfe one. A few careful experiments will fiirniftt a di¬ 
ligent perfon with more inftrudtions and knowledge on 
thofe particulars than all that can be written; 1 have 
however generally found, that lefs than two pounds 
weight of vitriolic acid, to each hundred weight of rag 
or pulp, hath been inefficient for the fineft, and that'more 
than five pounds weight was mifchievous to the coarfeft, 
having a tendency to take out ftrength as well as colour. 
The heat communicated to thefe retorts is by boiling 
10 3 
water, as before mentioned, being neither accompanied 
with the dirt, the expence, or labour, of land-heats, and 
much more uniform in its effects. Many circumrtances 
may happen to make feparate cafes and fire produce dif¬ 
ferent (hades, therefore, inftead of many cafes, I intend 
having only one, equal in dimenfions to all 1 propofe 
bleaching at a time ; witli retorts in proportion; with a 
trough of fome convenient fubftance, to hold the body of 
retorts in boiling water; and with a cover to confine in 
the fleam; by which means the heat will be retained, and 
the cold air kept from checking the afeent of the gaz 
when it becomes weak. A cafe of about twelve feet long, 
three feet deep, and twenty-eight inches wide, with about 
fourretorts, would bleach from fix to eight hundred weight 
at a time. After the article hath been expofed to the 
aflion of the gaz for eight or ten hours, it may be taken 
out of the cafes; and, if entirely freed from (heaves, it 
may be made into paper ; but, if any (heaves remain, it 
muft be again fubmitted to a fecond maceration, or boil¬ 
ing, and made into paper ; then finidied from the packs 
in the water-leaf or (lieet, as before particularized. In 
witnefs whereof, &c.” 
Thefe appear to be all the modern improvents as yet 
made in bleaching, founded upon the difeoveries of the 
French chemirts. But there has been a very ufefnl dif- 
covery lately made, by Mr. John Grimrtiaw, of Strines- 
Hall,,in the county of Derby, for bleaching printed, paint¬ 
ed, rtained, or dyed, cloths, &c. by means of vegetable 
fubrtances only ; and for clearing them of the impurities 
generally contracted in printing or rtaining them. For 
this difeovery he obtained a patent, which bears date the 
17th of February 1796, and deferibes the method as fol¬ 
lows:—“ I the (aid John Grimrtiaw do hereby declare, 
that the nature of my faid invention or difeovery is as fol¬ 
lows. The vegetable fubftances, in particular dates of 
preparation, to be ufed in clearing or bleaching, or affift- 
ing to clear or bleach, printed, painted, rtained, or dyed, 
cloths, or other materials, confiding of, or manufactured 
from, linen, cotton, hemp, filk, dr wool, or any two or 
more of them, and other printed, painted, rtained, or 
dyed, goods, manufactured or produced from animal or 
vegetable materials, or both, confift of the grains either 
of barley, wheat, oats, rye, or other corn, which remain 
after fuch barley, wheat, oats, rye, or other corn, has 
been made into malt, or brought into a fweet date ; and 
either brewed, for the purpofe of making ale, beer, or 
other malt liquor, or ufed for the purpofe of diftillation. 
Such grains, in all cafes, to be brought into a four date, 
either by keeping the fame without mixture until they be¬ 
come four; or by mixing the fame, either with four beer, 
or with alegar, or vinegar, or with cream of tartar, or 
with any other acid, in order to render the fame four. 
** The manner of ufing fuch four grains is, by putting 
three or four bufhels, or a greater or lefs quantity, of the 
fame, either into a copper or other pan or vetfel, contain¬ 
ing either two hundred gallons, or more or lefs, of water 
or other liquid, and either in a boiling or hot (fate, and 
putting four, or more, or fewer, pieces of fuch printed, 
painted, rtained, or dyed, cloths, or other materials or 
goods, into fuch mixture, and continuing the fame in fuch 
mixture either for five or ten minutes, or a greater or lefs 
length of time. This operation may be performed in a 
copper pan, exaCtly fimilar to thofe which are ufed by 
calico-printers, for the purpofe of clearing their printed 
calicoes, cottons, and linens, with bran ; and it renders 
the ufe of bran unneceflary. The operation may be greatly 
expedited by working the pieces quickly out of and into 
the mixture, by means of a winch or reel, placed acrofs 
the top of the pan or vert el above the mixture, over which 
winch or reel each of the pieces may be made to pad's. 
The winch or reel may be turned quickly round, either 
by the hand of a man, or any other power. The manner 
in which I generally exercife my invention or difoovery is 
as follows : I take any quantity of .common brewlionfe-, 
grains, fuch aS remain after ale or beer has been brewed 
1 o 
