Attention has already been called to the chief constituents of tea as far as their active principles are concerned. Of the active ingredients, tannin is the most abundant and caffein next. The quantity of moisture contained in ordinary commercial tea, which has been kept dry, rarely goes above 10 percent, and is usually about 5 percent.

The analysis of 63 samples of tea by Spencer in the Bureau of Chemistry, purchased on the open market, gave the following averages:

The chemical analysis of a tea, while it gives a correct notion of its composition, does not necessarily reveal anything respecting its character and comparative merits. All teas contain essentially the substances which have been mentioned in the table of analysis, but they vary greatly among themselves in palatability and character. It is difficult to determine the chemical characteristics of a tea on which its value depends. The terms flavor, strength and aroma are not associated with any definite ideas of chemical composition. In many cases, in fact, in all cases, the qualities of the tea do depend to a certain extent upon chemical composition. For instance, the astringency of a tea is due to its tannin; its exhilarating effect to its caffein; and its aroma to certain volatile principles, the nature of which is not well known. Usually the teas which have the larger quantities of these subtle matters are found to be the most valuable, but it is not true in all cases.