Obfervation hr Blue Colours. 95 
water; at firft the mixture was of a deeper green 
than that with the Pruffian blue digefted in Vitriolic 
Acid; and upon diluting it, at firft the liquor altered 
but little; yet, in the {pace of half a minute it be- 
came of a deeper blue than the original, but a large 
quantity of a dirty white coloured matter was 
feparated. 
It alfo appears, that there is very little difference 
between the pure mineral Alkali brought from the 
Eaft-Indies, and the beft Spanifh Barilla, when it is 
freed as much as poffible from common Salt. 
From the deep colouring matter feparating on the 
dilution of Pruffian blue, digefted with Vitriolic 
Acid, by adding water to it, Quere, Whether a 
much finer blue might not be produced by pour- 
ing off that blue liquor from the white powder, 
and edulcorating it 2 
