146 
which neither acids nor alkalis, nor even light itself> 
can change *. 
401. Many experiments of a similar kind were 
made by Dr Lewis. The colour of many blue 
flowers, he observes^ is extracted by water, but not 
by alcohol- } and the expressed juice, also, of such 
flowers, is for the most part blue. Both the blue 
juice and infusion are reddened by acids, and render-* 
ed green by alkalis and lime water. The red colour, 
produced by acids, at length fades by exposure ; and 
the green, produce^ by alkalis, changes to yellow* 
Red flowers impart their colour both to water and 
alcohol. The rose-coloured infusions were acted 
upon by acids nearly in the same manner as the 
blues j but the full deep reds were not. The deep 
infusion of red poppies was changed not to green 5 
but to purple, by alkalis. Yellow flowers give out 
their colour to water and alcohol ; but neither acids 
nor alkalis alter the species of the colour, though 
both of them vary its shade ; acids rendering it paler 
and alkalis deeper. The fine yellow dust of the an- 
thers of flowers gave a fine bright yellow to alcohol, 
and a duller yellow to water, which colours were 
heightened by alkalis, and turned red by acids. Even 
white flowers contain colourable matter, which 
is rendered green by alkalis, but not reddened by 
acids. The sulphurous acid vapour, which destroys 
the colour of other flowers, does not aflfect that of 
white ones f. 
* Mem. Phys. torn. iii. p, 107. 
f Neumann's Chen*, by Lewis, p, 430. et seq. 
