154 ADULTERATION AND DETECTION. 



however, this question is not of vital importance to the 

 analyst, as a solution may be arrived at from a determi- 

 nation 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 con- 

 denser; 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 1 50 C. 

 Having been maintained for a short time at this tempera- 

 ture 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 



