136 ADULTERATION AND DETECTION. 



with the aid of a microscope. (2) When only lightly 

 colored or suspected, place a sample of the leaves in a 

 cup or wine-glass and pour on briskly boiling water 

 and stir well for two or three minutes, then strain well 

 through a thin muslin cloth. The coloring-matter, if 

 any, will be found adhering to the cloth, that passing 

 through, sticking to the sides, or forming a sediment at 

 the bottom of the vessel into which it is strained. If 

 these deposits be treated with a preparation of chlorine, 

 or a solution of chloride of lime, and turn white, the 

 coloring substance used is indigo. But if treated 

 with a little potash, and it becomes brown, it will 

 prove to be Prussian blue, the application of a little 

 sulphuric acid having the effect of turning it blue 

 again. 



What are known to trade as " Canton Green teas " are 

 made from tea-dust and exhausted leaves ground up fine 

 and aglutinized with a preparation of gum, glue or other 

 starchy substance to unite and hold them together and 

 then artificially colored or glared. This fabrication is 

 readily detected by crushing the so-called leaves between 

 the fingers or rubbing them between the hands, upon which 

 they leave a yellowish-brown stain, greasy in nature. 

 Or by powdering a small quantity of the alleged leaves 

 and treating the dust with a dilution of sulphuric acid it 

 becomes very much discolored, and if it assumes a 

 leaden-blue color on the application of caustic potash it 

 is colored with Prussian blue. Again, place a small 

 quantity of the leaves in a cup or glass and pour on 

 boiling water, they will immediately begin to disintegrate 

 and form a thick, gluey deposit at the bottom of the 

 vessel. By treating this precipitate with a little iodine 

 the mass will become separated and dissolve into its 

 original dust. 



