time to time into this country, some of which has been known in the market by the name of the "Mahloo Mixture." Owing, however, to the rigid scrutiny to which tea is now subjected, it is likely that the quantity of such spurious teas passed into this country will become very small. It has been seen that the adulterants of tea may be conveniently studied under three heads—viz. : Ist. properties. Substances which can be detected by their physical 2nd. Mineral salts, along with some organic substances, all of which have distinctive chemical reactions. 3rd. Partially exhausted leaves. When tea is treated with hot water a large proportion of the soluble organic matter of the leaf is extracted, together with some of the mineral compounds, chiefly potash salts. If in a suspected sample the problem to be solved was merely whether it consisted wholly of exhausted leaves, the proof of sophistication would be very easy. But when a portion only of the tea is in that condition the question presents greater difficulty. This arises from the fact that in vegetable products, tea amongst the rest, nature has provided no hard-and-fast line as to the proportion in which the soluble or characteristic constituents may be present. Where a given test, say that of the total water extract is relied upon and applied to a number of teas, great difference exists between the maximum and minimum results. It is obvious, therefore, that a considerable admixture of a spurious tea could be added to one of the better kinds without reducing the amount of extract below that obtained from a genuine though inferior tea. It will be found difficult in practice to separate individual exhausted leaves. Where this can be done, the results of an analysis of them would no doubt be conclusive. Usually it is necessary to weigh out a given quantity—say 100 grains—of the tea, and after repeated extraction with boiling water, the filtered extract is evaporated down either in whole or in part, and the percentage of dry extract calculated. Or, 200 grains of tea are finely powdered in a mortar, and introduced into a flask with 2,000 grains of water at 60° F. (15.5° C.), and raised to the boiling-point over an argand burner. After this point has been reached, it is removed from the lamp, allowed to stand for 2 minutes, and filtered hot to prevent deposition of the tannate of theine. The specific gravity of the filtrate is then taken with a gravity bottle, and the result noted. The best filter for the purpose appears to be one made of flannel, and used double. SPECIFIC GRAVITY OF TEA INFUSIONS Made by extracting I part of dry Tea with 10 parts of Water at 60° F. (15.5° C.) raised to the boiling-point and quickly filtered. SPECIFIC GRAVITY OF INFUSIONS, Made by extracting I part of dry exhausted Tea with 10 parts of Water at 60° F. (15.5° C.), raised to the boiling-point and quickly filtered. PERCENTAGE OF EXTRACTIVE MATTER IN TEA DRIED AT 212° F. (100° C.). It will be seen that the range of specific gravity is very considerable in these teas. For purposes of comparison it would, however, be proper to compare the different classes of tea with each other. In the case of Congou (China), the gravities fall between 1009'80 and 1011*70. In green tea and Pekoes they fall between 1011'00 and 1014'50. If, therefore, exhausted leaves were added to good tea, the specific gravity obtained from the mixture would not fall below that given by a genuine poor tea, unless such leaves bore a somewhat high proportion to the genuine tea. This remark also applies, as has been already pointed out, to the estimation of the total extractive matter in tea, which varies to an equal if not greater extent. * As imported. TABLE OF TOTAL AMOUNT OF ASH In various kinds of Teas dried at 212° F. (100° C.), together with the Proportion of the Ash soluble in Water and insoluble in Acids, &c. Scented Orange Pekoe, com... 755 717 3:56 2.86 *56 2.11 '75 201 fine... 770 6.72 3.99 2.27 845 643 297 2.76 46 190 '70 1.80 '32 1.90 *29 2'04 76 172 68 179 '93 I74 2'33 *58 199 53 2.28 '62 1.56 43 184 7'08 6.70 3'54 254 Indian, Kaugra Valley Young Hyson 7 36 6 12 344 225 In the preceding results, which are selected from numerous analyses of average samples of genuine imported teas, the percentage of ash in no case, except one on page 10, reaches 8 per cent., while the sand in only a few instances exceeds 1 per cent. The amount soluble in water in only one case falls below 3 per cent.; in the majority of the teas the proportion lies between 3'20 and 360 per cent. As exhausted tea is deprived of a large part of the soluble salts, it follows that any serious admixture of such leaves would materially lower the percentage of soluble ash. The following table exhibits the percentage of ash, with the amount soluble in water, etc., found in tea-leaves which had been infused in the ordinary way for domestic use, and afterwards dried : PERCENTAGE OF ASH In used Tea-leaves with the Amount soluble in Water, etc. The table on the following page is founded on the analysis of unprepared tea-leaves received direct from India. |