1.50 
DYING. 
ploy a certain quantity of woad. But thefe abfurd re- 
ftrittions were at lad removed, and woad is now fcarcely 
tiled in dying, except as a ferment to indigo. The blue 
colouring matter, however, which it contains, mud, in 
all cafes, contribute confiderably to the dye. 
A diffident quantity of woad, mixed with bran, is put 
into the vat, filled with warm water, whofe temperature 
is kept up diffidently to endire fermentation. After¬ 
wards quicklime and indigo are added. The indigo is 
deprived of its oxygen, and diffolved by the lime. When 
the.folution is .complete, the liquid has a green colour, 
except at the furface, where it is copper-coloured, or 
blue, becaufe the indigo at the furface abiorbs oxygen 
from the air, and a (dimes its natural colour. The wool, 
or woollen-cloth, is dipped in, and palled through the 
liquid as equably as poffible ; thofe pieces being firlt 
dyed which are to aldime the.deeped (hade. Dyers ufu- 
ally enumerate thirteen different fliades of blue cloth, 
acquired by the different gradations of the colour in the 
vat. No part of the cloth lliould come in contaft with 
the fediment, which would fpoil the colour. When the 
cloth is tirff taken out of the vat, it is of a green colour ; 
but it foon becomes blue, by attracting oxygen from the 
air. It ought to be carefully waffied, to carry off the 
uncombined particles. This folution of indigo is liable 
to two inconveniences : i. It is apt fometimes to run too 
fait into the putrid fermentation : this may be known by 
the putrid vapours which it exhales, and by the difap- 
pearing of the green colour. In this date it would foon 
dedroy the indigo altogether. The inconvenience is re¬ 
medied by adding more lime, which has the property of 
moderating the putrefcent tendency. 2. Sometimes the 
fermentation goes on too languid. This defect is reme¬ 
died by adding more bran or woad, in order to diminifh 
the proportion of quicklime. 
Of YELLOW. 
The principal colouring matters employed to dye yellow, 
are weld, fujiic, and qucycitron bark. The rej'cda luteo/a, known 
in this country by the name of weld, is a plant which grows 
wild in mod European countries. Cultivated weld has 
a more (lender dem than the wild kind, but it is more 
valuable, becaufe it is richer in colouring matter. It is 
an annual plant, of a yellowifh green colour, furnifhed 
with a great number of final 1 leaves. Vt£hen ripe it is 
pulled, dried, tied up in parcels, and in that date fold to 
the dyer. Weld readily yields its colouring matter to 
water. The faturated decoction of it is brown ; but when 
fufficiently diluted with water it becomes-yellow. Acids 
render its colour fomewhat paler, but alkalies give it a 
deeper (hade. When alum is added to it, a yellow colour¬ 
ed precipitate falls down, confiding of alumina combined 
with the colouring matter of weld. The affinity, there¬ 
fore, of this colouring matter for alumina is (o great, that 
it is able to abftradt it from fulplutric acid. Its affinity 
for oxyd of tin is at lead equally great; for muriat of tin 
caufes a copious bright yellow precipitate, compofed of 
the colouring matter and the oxyd combined. Mod of 
the metallic falts occalion fimilar precipitates, but vary¬ 
ing in colour according to the metal employed. With 
iron, for indance, the precipitate is dark grey, and with 
copper brownifh green. 
The morus tinEloria is a large tree which grows in the 
Wed-India iflands. The wood of this tree is of a yellow 
colour, with orange veins. The French call it yellow 
wood, (ben's jaune ■,) but the Englifh dyers have given it 
the name of fujiic. This wood has been introduced into 
dying linee the difeovery of America. The precife time 
is not known ; but that it was ufed in England foon af¬ 
ter the middle of the feventeenth century, is evident front 
fir William Petty’s paper on Dying, read to the royal l'o- 
ciety foon after its inditution. Fudic gives out its co¬ 
louring matter with great facility to water. The faturated 
decoftion of it is of a deep reddifh yellow colour; when 
fufficiently diluted, it .becomes orange yellow. Acids 
render it turbid, give it a pale yellow colour, and oc- 
cafion a flight greenilli precipitate, which alkalies re-dif- 
folve. Alkalies give the decoftion a very deep colour, 
inclining to red ; fome time after they have been added, 
a yellow matter feparates from the liquid, and either 
fwims on the furface, or adheres to the fides of the vef- 
fel. Alum, fulphat of iron, of copper, and of zinc, pro¬ 
duce precipitates compofed of the colouring matter com¬ 
bined refpeCtively with the bafes of thefe different falts; 
and the colour varies according to the fubftance with 
which this colouring matter is combined. With alumina 
it is yellow ; with iron, yellowifh brown; with copper, 
brownifh yellow ; and with zinc, greenifh brown. 
The quercus nigra, to which Dr. Bancroft has given the 
name of quercitron , is a large tree which grows Cpontane- 
oully in North America. Dr. Bancroft difeovered, about 
the year 1784, that the bark of this tree contains a great 
quantity of yellow colouring matter, and fince that time 
it has been introduced into dying with much advantage. 
To prepare it fqr the dyer, the epidermis is fhaved off, 
and then it is ground in a mill. It feparates partly into 
flringy filaments, and partly into a fine light powder. 
Both of thefe contain colouring matter, and therefore are 
to be employed ; bj.it, as they contain unequal- quanti¬ 
ties, they fliould be ufed in their natural proportions. 
Quercitron bark readily gives out its colouring matter 
to water at the temperature of 100°. The infufion has a 
yellowifli brown colour, which is rendered lighter by 
acids, and darker by alkalies. Alum occafions a fcanty 
precipitate of a deep yellow colour; muriat of tin, a co¬ 
pious bright yellow precipitate ; fulphat of tin, a dark 
olive precipitate; and fulphat of copper, a precipitate 
of a yellow colour inclining to olive. 
Befides thefe yellow dye-fiuffs, there are others occa- 
fionally ufed by dyers. The following are the mod re¬ 
markable : Cenijla tinEloria, or dyers broom : yields a very 
inferior yellow, and is only ufed for coarfe woollen (luffs. 
Serratula tinEioria, or faw-wort: yields a yellow.nearly of 
the fame nature with weld ; for which, therefore, it is a 
good fubftitute. Juglans alba, or American hiccory : the 
bark of which yields a colouring matter fimilar to that 
of quercitron bark, but much (mailer in quantity. Anotta 
is a name given to a red pafie formed of the berries of 
the bixa orellana, a tree which is a native of America. 
This pafie yields its colouring matter to a folution of alkali 
in water. The folution affords an exceedingly beautiful 
yellow dye, but very fading, and incapable of being fixed 
by any known mordant. Turmeric is the root of the 
curcuma longa, a plant which grows both in the Eafi and 
Weft: Indies. It is richer in colouring matter than any 
other yellow dye-ftuff. It yields very beautiful yellows, 
but too fading to be of much life, and no mordant has 
any influence in contributing to their permanence. 
Yellow colouring matters have all too weak an affinity 
for cloth, to produce permanent colours without the life 
of mordants. Cloth, therefore, before it be dyed yel¬ 
low, is always prepared by combining fome mordant with 
it. The mordmt moft commonly employed for this pur- 
pofe is alumina. Oxyd of tin is fometimes ufed when 
very fine yellows are wanted. Tan is .often employed as 
a fublidiary to alumina, in order to fix it more copioufly 
on cotton and linen. Tartar is alfo ufed as an auxiliary 
to brighten the colour; and muriat of foda, fulphat of 
lime, and even fulphat of iron, in order to render the 
(hade deeper. The yellow dyed by means of fuftic is 
more permanent, but not fo beautiful as that given by 
weld or quercitron. As it is permanent, and not much 
injured by acids, it is often ufed in compound colours 
wliere a yellow is required. The mordant is alumina. 
When the mordant is oxyd of iron, fuftic dyes a good 
permanent drab colour. Weld and quercitron bark yield 
nearly the fame kind of colour ; but, as the bark yields 
colouring matter in much greater abundance, it is much 
more convenient, and, upon the whole, cheaper .than 
weld. It is probable, therefore, that it will gradually 
iuperfede 
