Obfervations on Blue Colours. 89 
formed; but upon adding more of the folution, a 
fine blue colour was produced which readily preci- 
pitated. This being wathed frequently with water 
till the fupernatant liquor was_quite tafielefs, was 
then dried, and produced the colour No. 1. 
As I was defirous of feeing whether Roch Alum 
would have any different effect, four ounces of Roch 
Alum and one ounce of Martial Vitriol were diffolved 
in two quarts of water, by boiling them together, 
and with fome of this folution a precipitate from the 
Mother-water of Soda Phofphorata was produced, 
which, after it was well wafhed, yielded the blue 
Colour No. 2, which is ofa very pale hue. 
A fmall quantity of thefe powders was given to a 
perfon that paints in water colours, who on trying 
sthem faid they were too fpongy for that purpofe. 
As there was a very copious, light precipitate pro- 
duced in the above two experiments, andthe colouring 
matter, when dried, but fmallin quantity ; ] evaporated 
the Mother-water of Soda Phofphorata to a thick pelli- 
cle, and a deliquefcent falt was produced: ithe remain- 
ing liquor was precipitated with a folution of common 
Alum and Martial Vitriol, made with the propor- 
tions above-mentioned. A precipitate, not fo light 
as the two others, and in appearance lefs in quantity, 
was produced, but which, when wafhed and dried, 
yielded about the fame weight as the others. It was 
of a paler blue than the firft production, but of a 
bright colour; fome of which is contained in the 
paper marked No. 1, witha +. 
M This 
