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Receipt for making the yellow dye. 
Take \ powdered indigo, and mix it in a 
high glafs veffcl, with 5 2 of ftrong fpirit of nitre, 
previouily diluted with 5 8 of water j let the mixture 
ftand for a week, and then digeft it in a fand heat 
for an hour or more, and add ^ 4 more of water to 
it; filter the folution, which will be of a fine yellow* 
colour. 
Strong fpirit of nitre is liable to fet fire to indigo ; 
and it is on that account that it was diluted with 
water, as well as to hinder its frothing up. 5 2| 
of ftrong fpirit of nitre will fet fire to ^ | of indigo ; 
but, if it be highly concentrated, a Ids quantity will 
fuffice. 
If the indigo be digcfled twenty four hours after 
the fpirit of nitre is poured on it, it will froth and 
boil over ; but, after ftanding a week or lefs, it has 
not that property. 
One part of the folution of indigo in the acid of 
nitre, mixed with four or five parts of water, will 
dye filk or cloth of the paled yellow colour, or of 
any fhade to the deeped, and that by letting them 
boil more or lefs in the colour. The addition of 
alum is ufeful, as it makes the colour more lading ; 
according as the folution boils away, more water 
mud be added. 
None of the colour in the operation feparates from 
the water, but what adheres to the filk or cloth ; 
of confequence this colour goes far in dying. 
Cochineal, Dutch litmus, orchel, cudbear, and 
many other colouring fubdances treated in this man- 
ner, will all dye filk and wool of a yellow colour. 
VoL. LXI. S The 
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