gz Colours from Vitriol . 
and therefore a few Tea Leaves put to 
ffceep for fome Minutes in any Mineral 
Water made hot, will readily difcover if 
it contains Vitriol, by fuch its Change of 
Colour : the Proportion of the Vitriol may 
likewife be guelfed at by the Deepnefs or 
Palenefs of the Tincture. 
On writing with a Solution of Green 
Vitriol, nothing is feen upon the Paper 
when dry: but by rubbing it over with 
a Decoction of Galls, what was written 
becomes black and legible. Spirit of Vi¬ 
triol wiped gently upon this, makes it 
vanifh again immediately : Oil of Tartar 
fer deliquium restores the Letters once more, 
though not black but yellowilh -f-. 
A ftrong Decodtion of red Rofes mixed 
with a Solution of Vitriol produces a black 
Ink, which on dropping Spirit of Nitre 
into it becomes inilantly red, and is far¬ 
ther convertible into a greyilh Liquor, by 
adding a little of the volatile Spirit of Sal 
Armoniac. 
Good Writing Ink being not always or 
every where to be procured, it will not 
perhaps be unacceptable to give here an 
eafy Way of making it, which I can re¬ 
commend from many Years Experience. 
To one Quart of Rain Water, or foft 
River Water, put four Ounces of blue 
* Vide Lemry's Chemiftry, chap, iS. 
Galls 
