126 
leaves, when immersed in water charged with these 
several acids -, for they exhibit, at first, a fawn co- 
lour, and then become white ; but etiolated leaves 
are not sensibly affected*. We observed, in some 
instances, that the green leaf not only became yellow 
or brown in acid liquors, but the liquor itself acqui- 
red a reddish hue. These effects of acids on the co- 
lours of leaves are also visible in common culinary 
processes ; for waters, denominated hard, from con- 
taining an excess of acid, greatly discolour the vege- 
tables which are boiled in them ; and the green co- 
lours of pickled vegetables are very much degraded 
by the action of the acid liquor in which they are 
preserved. 
375. As acids are thus found to discharge the 
green colour of plants, so alkalis may be expected to 
improve it; and experience confirms the expectation. 
If green leaves, says M. Senebier,"be plunged in al- 
kaline liquors, they preserve their colour, and the li- 
quor acquires a greenish tint. Leaves rendered yel- 
low by decomposition become brown in alkaline 
fluids ; but etiolated leaves, and those which are red- 
dened by age, pass to a green, though this did not 
happen to the etiolated leaves of the French bean f. 
We observed, that if water of potassa, or muriate of 
soda, was added to the water in which green leaves 
were infused, it improved their colour ; but if the 
green colour was first degraded by the action of the 
water, these substances did not restore it. 
376. If, then, it be established, by the' foregoing 
* Mem. Chim. torn, ii- p, 147. I Ibid, p. 14 V Q. 
