H4 
Mr. Smithson on the colouring 
After this treatment the paper remained brown ; seem- 
ingly such as it was before being dyed blue. 
It should seem that there are at least two colouring matters 
in this paper; one red, which is extricable from it by water; 
the other blue, which requires the agency of an acid to ex- 
tract it. 
Its insolubility in water, and low degree of sensibility to 
acids, distinguish the blue matter from turnsol ; to which its 
not being affected by alkalis otherwise much approximate it. 
Its easy solubility in dilute sulphuric acid, and being reddened 
by it and several other acids, show it not to be indigo. 
Of the black mulberry. 
The expressed juice of this fruit is of a fine red colour. 
Caustic potash made it green, which gradually became 
yellow. 
Carbonate of soda did not make it green, but only blue. 
Carbonate of ammonia changed it to a vinous red, rather 
than to blue ; and this redness increased on standing. 
Caustic ammonia made it bluer than its carbonate ; but, on 
standing, the mixture became of the same vinous red. 
The mulberry juice mixed with carbonate of lime became 
purple. On filtering, a red liquor passed ; and the carbonate 
of lime left on the filter was blue. An addition of whitening 
to the red filtered liquor did not alter its colour ; nor did this 
second portion of whitening become blue. Heating did not 
affect the red colour of this liquor ; so that it was not owing 
to carbonic acid, disengaged from the carbonate of lime. 
Caustic potash instantly made this red liquor a fine green, 
and gradually yellow. 
