ADULTERATION AND DETECTION. 



To still better distinguish between them treat a sample 

 of the suspected tea as in making an ordinary infusion to 

 soften and expand the leaves, then separate and uncurl them 

 and lay flat on a piece of glass or other smooth surface 

 for comparison with the genuine leaf. Next see that they 

 agree in description and formation, but more especially in 

 the venations and serrations. Or soak the leaves in hot 

 water, and carefully unroll and closely examine their for- 

 mation and structure and then compare closely. The 

 epidermis of the lower surface of the true leaf can be 

 with a little caution detached in small portions with a 

 sharp razor, and then analyze the frame or skeleton of 

 the leaf in a little water or glycerine, under a microscope, 

 comparing the venations and serrations with those of the 

 genuine tea-leaf. Still another simple and inexpensive 

 test is to boil a few of the suspected leaves for a minute 

 or two on a watch glass, with a little distilled water, and 

 add an equal portion of burnt magnesia, treating the 

 whole until it is reduced to a large-sized drop. If no 

 crystalline sublimate is obtained therefrom by the opera- 

 tion the leaves cannot be those of genuine tea. 



Chemically an examination of the ash of tea-leaves 

 also affords some criteria which may also be utilized for 

 the purpose of identifying the true tea-leaf. For instance, 

 in common kinds of wood, such as oak, deal and pine, 

 the proportion of ash is a few-tenths per cent, of the 

 whole, and by taking wood in its ordinary air-dried con- 

 dition it contains some 20 to 30 per cent, of moisture. 

 Leaves, on the other hand, contain 10, 20 and even 30 

 times as much mineral matter, there being doubtless a 

 connection between this abundance of mineral matter 

 and the active chemical changes which take place in the 

 leaves during the growth of the plant. In tea-leaves, 

 therefore, as in leaves in general, the ash amounts to a 



