64 WRITINGS OF JAMES SMITHSON. 



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. 



Sulphuric, nitric, and marine acid, made it red. Carbon- 

 ate of lime added to a reddened solution, restored the green 

 colour, which therefore appears to be the proper colour of 

 the substance. 



The green colour, which the last infusions of galls present, 

 appears to be different, both from the usual green of vege- 

 tables, and from sap green. 



Some animal greens. 



A green puceron, or aphis, being crushed on white paper, 

 emitted a green juice, which was immediately made yellow 

 by carbonate of potash (wrongly called sub-carbonate.) 



There are small gnats of a green colour : crushed on 

 paper, they make a green stain, which is permanent. 

 Neither muriatic acid nor carbonate of soda altered this 

 green colour. It is consequently of a different nature from 

 the foregoing. 



