matters of some vegetables. 113 
plumbs, and, I think, of the scarlet geranium, and of the 
pomegranate tree. 
The red cabbage, and the rind of the long radish are also 
coloured by this principle. It is remarkable that these, on 
being merely bruised, become blue ; and give a blue infusion 
with water. It is probable that the reddening acid in these 
cases is the carbonic; and which, on the rupture of the 
vessels which enclose it, escapes into the atmosphere. 
Of sugar-loaf paper. 
This paper has been employed by Bergman as a chemical 
instrument. I am ignorant of what it is coloured with. 
Sulphuric, muriatic, nitric, phosphoric, and oxalic acids 
make it red. Tartaric and citric acids, made rather yellow 
spots than red ones. Distilled vinegar, and acid of amber, 
had no effect on it. 
Carbonate of soda and caustic potash did not alter the 
blue colour of this paper. 
Water boiled on this paper acquired a vinous red colour; 
carbonate of lime put into this red liquor, did not affect its 
colour : nor did carbonate of soda or caustic potash change 
it to blue or green. 
Cold dilute sulphuric acid extracted a strong yellow tinc- 
ture from this boiled paper : carbonate of lime put to this 
yellow tincture made it blue ; but on filtering.the liquor which 
passed was of a dirty greenish colour.; and sulphuric acid 
did not make it red: a blue matter was left on the filter, 
which was not made red by acetous acid ; but was so by 
sulphuric. 
Q 
MDCCCXVIII. 
