94 _. An Account of, and 
except in-the fingle one made with Rock Allum; for 
the other operations have been repeated, and the 
refults have been uniform. 
The Acid of Phofphorus has been tried with the 
two precipitating liquors, and no blue colour was 
produced. It therefore remains to account, how 
this blue colour fhould be continually produced by 
the combination above-mentioned, efpecially as the 
phofphoric Acid was obtained from bones burned. 
to a perfect whitenefs, which might be expected to 
deftroy the tinging principle. | 
Some of the beft Pruffian blue that could be 
purchafed, was added to the ftrong Vitriolic Acid. 
It was changed to a green colour, but much paler 
than that produced from the colour precipitated by 
the Martial Solution, as above related, by adding the 
Acid of Vitriol to it; but on diluting the Pruffian 
blue, digefted in the Vitriolic Acid, with water, a 
large quantity of white powder was perceived, which 
evidently muft be the Earth of Alum. Upon 
further diluting and ftirring the mixture, it readily 
mixed with the tinging matter, and appeared uni- 
formly blended therewith. 
A portion of the blue colour, No. 1. was like- 
wife digefted with ftrong Vitriolic Acid. It was 
changed toa darker green colour than in the laft 
mentioned procefs, but on diluting it with water, 
it changed uniformly to blue: but on digefting 
fome of No. 2 with the Vitriolic Acid, there was 
a feparation when the mixture was diluted with 
water ; 
