Founded on these observations an assay of the tea-extract may be made by the following simple process: Put ten grams of tea into a pint flask and pour on about two-thirds of distilled water accurately measured, a cork and bent tube is then adapted to the mouth of the flask and a connection made with a condenser. The contents of the flask are next heated and made to boil strongly. That having been done the boiling is stopped and the flask and condenser disconnected and the distillate poured back into the flask and the decoction of tea observed closely. If quite clear fifty grams are weighed out and evaporated to dryness in a water-bath and weighed till constant. If the decoction be not quite clear by this time it is to be filtered hot; the first small filtrate is best thrown away and the filtrate collected, weighed, and dried in the water-bath until the residual tea-extract becomes quite constant. Having performed the operation in the manner directed, the weight of the tea-extract actually weighed will be the weight of the extract yielded by one gram of the sample to be assayed.

But in coming to a decision as to the genuineness of a sample of tea of which an analysis has been made by this method, it is of importance to remember that genuine tea is subject to considerable variation in composition. The quality and condition of the leaf at the time of gathering and the different treatments which it undergoes in the process of manufacture, or whether the tea is Black or Green, cause the composition to exhibit a wide range of variation. Taking the percentage of the extract as a basis from which to start, that in genuine tea being from 32 up to 50 per cent. in its ordinary commercial condition. Such being the case, it is obvious that a determination of the percentage of extract will not enable the expert or analyst to say whether the sample of tea be of a lower or higher grade of pure tea, or whether it is composed of a high grade of genuine tea and a portion of exhausted leaves. In a general way, however, this question is not of vital importance to the analyst, as a solution may be arrived at from a determination of the soluble ash, which would be found rather deficient on incineration. For although tea may be exceptionally rich in extract, and although there are difficulties in the way of deciding whether a given sample of tea consists of average quality or of fine tea mixed with spent tea, there are no such difficulties in recognizing the case of tea of average grade, mixed with a considerable quantity of exhausted leaves, as it is assumed in this formula that the soluble ash in genuine tea is 3.6 per cent. and that in spent tea only 0.3 per cent. But in using this formula it must be understood that the results are only rough approximations, judgment and discrimination being required to determine by it.

Tea-extract yields a comparatively large quantity of ammonia when it is boiled with potash and permanganate of potash, and it is probable that this character may prove very valuable also in testing the purity of tea, for which purpose a solution containing about 10 per cent. of solid potash, free from ammonia and nitrogenous matter, is required and easily obtained. Ten grams of this solution of potash is put into a small flask-retort, working in an oil-bath and connected with a small condenser; the whole apparatus to be carefully freed from the last traces of ammonia, which is best accomplished by distilling the water through it, after which from 5 to 10 parts of the tea infusion are poured into the retort, which is then corked up and heated in an oil-bath to 150 C. Having been maintained for a short time at this temperature it is then lifted out of the bath and some pure water poured into the retort, which is again to be heated in the oil-bath. More than half of the water is then distilled over and in this manner the “free ammonia” is obtained from the distillate. When this has been accomplished some of the potash and permanganate solution is added to the contents of the retort and distilled so as to yield a distillate containing “albuminoid ammonia,” the result being as follows in pure teas:—

Free ammonia,0.28milligrams.
Albuminoid ammonia,0.43“
——
Total,0.71milligrams.

While the extract from a sample of spurious leaves yielded of

Free ammonia,0.20milligrams.
Albuminoid ammonia,0.295“
——
Total,0.495milligrams.

This experiment is made with the greatest ease, and will also be found valuable by brokers and others interested in tea for testing the strength of the tea-infusion. As has already been observed, tea is also remarkably rich in nitrogen, so much so that a determination of nitrogen may be resorted to as a means of identification. With this object it is best to take a sample of tea, first mixing it up well and powder it in a mortar. Of this tea-powder some 0.3 grams should be accurately weighed out. This is then to be mixed with some 50 grams of oxide of copper, which has been first oxidized without the employment of nitric acid, and which shortly before using had been ignited and allowed to cool. A combustion-tube of hard German glass, closed at one end and perfectly clean, is next charged as follows: At the closed end a layer, some three to four inches in length, of a mixture of dry bi-carbonate of soda and fused bi-chromate of potash is placed, the mixture being intended to give out carbonic acid. Next to this compound place two inches of oxide of copper, then the mixture of tea and oxide of copper, then more oxide of copper and some clean metallic copper on top, then a perforated cork and exit tube, which dips under the mercury, and place the combustion-tube in an appropriate furnace to heat. By heating the layer of carbonate of soda and bi-chromate of potash, carbonic acid is caused to traverse the tube and expel the air from it. This having been done the tube is next heated gradually from before so as to burn up the tea, the gases being collected over the mercury. At the end of the operation the carbonic acid is once more made to traverse the tube by again heating the mixture at the back, all the nitrogen being driven from the tube and collected. Finally the carbonic acid is absorbed by means of the potash and, the residual nitrogen gas is measured with well-known precautions. This gas should also be tested for bin-oxide of nitrogen by means of oxygen and pyro-galate of potash, any bin-oxide of nitrogen gas to be measured and allowed for in the test.

Among the most common forms of adulteration practiced by dealers in this country is that of substituting old and valueless Young Hysons for Japans or mixing them together the better to disguise the fraud. The mixing or blending of old, stale, weedy or smoky Congous with Oolongs, particularly when such teas become a drug on the market. The reduction of Moyunes by the addition of Pingsueys in the proportions of half and half and then refacing them as “True Moyunes.” The refacing of Ningyongs and other Amoys as Formosas being still another form, for which at the present low prices of the commodity there is not the slightest occasion. The most recent “trick” of the tea trade being that of mixing Japan Nibs with Twankays and Hysons, the latter, I regret to add, being now extensively adopted by at one time reputable houses.

Some law should be passed in this country to ensure the public against the possibility of purchasing spurious and adulterated teas as in Russia, where the dealers are compelled to sell their teas under government labels placed on the packages by experts appointed by the Government for that particular purpose and who work under official inspectors, the expense of examining and labeling being defrayed out of the revenue realized from the sale of the labels to the dealers. To such an extent was the nefarious practice carried on in that country that the adoption of this system became imperative in order to restore the confidence of the public in the genuineness of the tea offered for sale, with the result of having materially checked the traffic in spurious and adulterated teas in that country.