DYEING. 
In order to dispose cotton to receive the 
dye, it must be first scoured ; some boil it 
ill sour water, but more frequently alkaline 
ley is used ; the cotton must be boiled in it 
for two hours, and then rung out, after- 
wards be rinsed in a stream of water till the 
w'ater comes olf clear, and then be dried. 
The cotton stutfs, which are to be prepared, 
must be soaked for some time in water, 
mixed with at most one- fiftieth of sulphuric 
acid, after which they must be carefully 
washed in a stream of water and dried. 
The acid employed in this operation has 
been observed to take up a quantity of cal- 
careous earth and iron, which would have 
injured the colours. 
Aluming and galling are generally neces- 
sary in dyeing cotton and linen. 
In the preparation with alum, about four 
ounces of it are required to each pound of 
the stuff'. It must be employed with the 
precautions mentioned in the last article ; 
some add a solution of soda in the propor- 
tion of one sixteenth of the alum, others a 
small quantity of tartar and arsenic. The 
thread is well impregnated by working it 
pound by pound in this solution. It is then 
put altogetlier into a vessel, and what re- 
mains of the liquor is poured upon it. It 
is left there for twenty-four hours, and then 
removed to a stream of water, where it is 
suffered to remain for an hour and a half, or 
two hours, in order to extract a part of the 
alum, and it is then washed. In this ope- 
ration the cotton gains about one fortieth 
of its weight. 
In the operation of galling, different 
quantities of galls, or other astringents, are 
used, according to the quality of the astrin- 
gents, or the effect desired. The galls 
powdered, are boiled for about two hours 
in a quantity of water proportioned to that 
of the thread to be galled ; the liquor is 
then suffered to cool to a temperature, 
which the hand can just support, after 
which it is divided into a number of equal 
parts, that the thread may be wrought 
pound by pound, and what remains is 
poured upon the whole together, as de- 
scribed in the process of aluming. It is 
then left for twenty-four hours, especially 
when intended for maddering for black, but 
for other colours twelve or fifteen are suffi- 
cient. After this it is to be wrung out and 
dried. When stuffs are to be galled, which 
have already received a colour, the opera- 
tion must be performed in the cold, that 
the colour may not be injured. Cotton 
w'hich has been aliimed, acquires more 
weight in the galling, than that which has 
not undersone that process. Although alum 
adheres but in small quantities to cotton, it 
gives it a greater power of combining botl» 
with the astringent principle, and the co- 
louring matter. 
Of Flax. 
As flax and hemp possess the same pro- 
perties as far as relates to dyeing, tire direc- 
tions for one will succeed equally well for 
the other. 
Flax must undergo several preparations 
before it is fit to receive the dye ; the first 
is the watering, by which the fibrous parts 
of the plant become disposed to separate, 
so as to be rendered fit for spinning. 
In watering, a glutinous juice, which 
holds the green colouring part of the plant 
in solution, and which is the medium of 
union between its cortical and ligneous 
parts, undergoes a greater or less degree of 
putrefaction, according to the mode of con- 
ducting the operation. This process is per- 
formed to the greatest advantage in pits 
situated on the banks of rivers, where the 
water may be changed often enough to pre- 
vent a degree of putrefaction that would 
injure the flax, and be prejudicial to the- 
workmen, yet not so often as to hinder the 
degree of putrefaction necessary for ren- 
dering the glutinous substance soluble in 
water. After watering, tlie flax is, dried, 
and the ligneous part separated by a mecha- 
nical operation. 
Some have proposed the mixing a small 
quantity of caustic alkali with the water to 
increase its solvent power, but it appears, 
from Dr. Home’s experiments, that the al- 
kali retards the operation, and renders the 
flax liable to break. But after the watering 
and drying, alkaline substances dissolve the 
greatest part of the colouring matter, on 
account of the change it has rtndergone 
from the exposure to air and light, and the 
consequent absorptiorr of oxygen. 
The processes published by the Prince of 
S. Sever for obtaining fine dre.ssed hemp, de- 
pend on the solution of the colouring mat- 
ter by alkali. He directs that dressed 
hemp be lixiviated in a solution, of two 
parts soda and one of lime, then impreg- 
nated with soap, and kept in digestion ; 
and afterwards well washed and hackled; but 
in this process only that portioir of the 
colouring matter is dissolved, which would 
have been carried off’ by the first leys used in 
the beginning of the bleaching of the cloth. 
