n6 Mr. Smithson on the colouring 
Caustic potash made it green. 
Caustic ammonia seemed not to have more effect on it than 
carbonate of soda. 
Some poppy petals being bruised in a mixture of water 
and marine acid, formed a florid red solution : a superabun- 
dance of chalk added to this red liquor, did not make it blue; 
but turned it to a dark red colour exactly like port wine. 
Some poppy petals bruised in a weak solution of carbonate 
of soda, and the mixture filtered, the liquor which came 
through was not at all blue, but of a dark red colour like 
port wine. Caustic potash made this red liquor green, which 
finally became yellow. 
Some dried poppy petals of the shops, gave a strong 
obscure vinous tincture to cold water. This red tincture 
heated with whitening, did not alter to blue, but preserved 
its red colour. 
These very imperfect experiments may perhaps suggest 
the idea, that the colouring matter of this flower is the same 
as the red colouring matter of the mulberry. 
Of sap green. 
The inspissated juice of the ripe, or semi-ripe, berries of 
the buckthorn, constitute the pigment called sap green; by 
the French, vert de vessie. This species of green matter is 
entirely different from the common green matter of vege- 
tables. 
It is soluble in water. 
Carbonate of soda and caustic potash changed the solu- 
tion of sap green to yellow. Paper tinged by sap green is a 
sensible test of alkalis. 
