DIPPING, 
whatever, “The theory is 2 clea and the pradtice, to 
ar acquainted with the theory, fo very obvious, that 
common care and Reine it is fearcely poffible to 
cr? ° 
ndtgo, as we have jut before obferved, is -_ in 
the a: lies and alkaline earths, till de a 
n adding together, there- 
and lime, in {uitable proportions, the 
exygenates it, and renders it foluble in the lime, which, if in 
fufficient quantity, immediately diflolves it. The oxyd of 
iron, which has ferved to deprive the poe of its. ee 
the fulphate of lime formed by th the with 
re than 
there remains in folution ooly 
fie nd ne bafe of aaine. There are few dyers and cali- 
co-printers who do not imazine that folution of indigo 
confifts <7 all the fubfances that have 
er domjnate, as a very fim- 
ple experiment will fh i ar lime water, and 
copperas water together, and an inftant precipitation 
will nae lace. as any copperas remains in 
folution, every fucceffive addition of lime water will caufe a 
frefh pent te which confifts of oxyd of iron, and ful- 
phate of lime, formed by the union of the lime with the 
acid of the copperas. ne of the lime remains in folution. 
cid t 
The folution wil 
r only. o thofe 
the leaft acquainted vi the principles of ier thefe 
nec ee 
with clear 
and on the ftrength of the folution auired. The eat 
of indigo varies greatly, fome kinds, as the fine Spanifh and 
Eaft India, containing tw wice, and even thrice, as much co- 
jouring matter as the coarfer kinds. In general from two to 
five pounds of good indigo to every hundred gallons of wa- 
ter, are fuflicient to form vats for moft purpofes, bake 
fometimes, but rarely, required Aron er; 49 pounds in a 
vat holding 800 gallons, will produce a folution of fufficien nt 
intenfity to give a black nearly, at four or five immer- 
ns. 
The finer the quality of the indigo, and the greater the 
eral of copperas and lime, neceffary to | its fo- 
lut In general, however, one of ancy two 
pees, aaa two of lime, are confidered as the beft Renee 
and as fuch € giv en by Berthollet, who, to profound 
chemical fence, waite confderable practical knowledge, 
and the beft deseo aos the proceffes of the 
yers and calico-print 
The indigo is pe evcolly Soins. in a mill with water, till 
it is reduced to a {moo 
i of aggregation, it is fca all, 
attacked by coppers eo lime 3 ; all therefore that = se 
the a into the vat in a Iumpv 
Ever 
againft this, and when by rubb'nz it between the fingers, or 
on a pane of glafs, it appears fine and {mooth, and free from 
{mall hard, gritty aah eee it may be removed from the 
mill, mixed u or five times its ay : waters 
y lumps 
e vat having reccived its charge of it. and been 
filled up with clean water, 
is diffolved, the lime is added, and the vat well raked 
till all its contents are intimately mixed, the lime diflulved 
and the copperas decompofed. ig action of oxyd of i iron 
upon indigo requires time, and a 
©x 
0 thus brought more within the {phere 
of chemical os than when Heating in the whole mals of 
water int the 
PP 
merce ; at its maximum, or fecond ftate of oxydatio 
ms an orange-coloured, unerytalizable folanen otto 
ee —— properties from the for 
The n folution is ditinguifhed i= its great avidity 
for exe aod its difpofition to pafs to the orange, or fully 
 oapeenaed ftate. Itis this affinity for oxygen that fits it 
for the folution of indigo. © copperas of commerce is 
however not unfrequently a mixture of the two falts or oxyds 
a porti g acquired 
erhaps by too gre 
In ieee cafe re furface ia covered with a 
orange ruft, and a portion of the falt is rendered atlefs for 
the blue vat having already acquired its maximum of oxygen. 
The chief difference in the quality of copperas, is how- 
ever in the more or lefs ‘igus ag anaes of the acid, form- 
ing two diftin@ falts, which w i i 
e by manufacturers long before henita were acquainted with 
their exiftence. The fir 
reen, and contai 
e ers imagine 
coloured copperas is the beft, or, as they ‘tay, the frrongef, 
prejudice which the manufacturer Bes eafily accommodate 
by fprivkling a little fine fifted quick lime over the farace, 
which foon covers it with a coat of orange ruft. 
oat 
The lime ufed for the fee vat fhould be quick. ae 
