156 ADULTERATION AND DETECTION. 



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 prac- 

 ticed by dealers in this country is that of substituting 

 old and valueless Young Hysons for Japans or mix- 

 ing them together the better to disguise the fraud. The 

 mixing or blending of old, stale, weedy or smoky Con- 

 gous 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 lat- 

 ter, I regret to add, being now extensively adopted by at 

 one time reputable houses. 



