1-22 



in a few cases, assuming an olive green tint. The coloured particles 

 were numerous, and seem in a state of very minute division of a deep 

 blue and brownish yellow colour. 



All the samples examined were tested with potassa, under the micro- 

 scope, and in every case it was found that the blue grains were con- 

 verted into a dirty yellowish colour ; while, upon the yellow granules, it 

 had no effect whatever, except in one case, in which a few deep orange- 

 colom*ed particles assumed a much paler hue. On adding a dilute acid 

 to the alkaline mixture thus produced, the originally blue particles 

 resumed their former colour, but no change could be perceived with 

 regard to the yellow grains. Chlorine water was also employed, but in 

 no case had it the effect of bleaching the blue grains, therefore they 

 could not consist of indigo. 



We may conclude from these experiments, that the powder producing 

 the " bloom " upon green tea is composed of a white crystaline powder, 

 coloured with Prussian blue, and some yellow pigment, not however 

 turmeric, as has been affirmed by some writers, for, in that case, the 

 addition of an alkali would have turned them brown, instead of which it 

 had either no effect at all, or, as in one case, a contrary effect was pro- 

 duced, a paler coloming being the result ; and that it is therefore of a 

 mineral, and not a vegetable origin, and, in all probability, consists of 

 chrome yellow, yellow ochre, or, as some say, possibly Dutch pink. Since 

 the experiments from which these conclusions were drawn, a sample of the 

 powder used by the Chinese has been obtained : it is an extremely fine 

 apple-green powder, and, when examined under the microscope, presents 

 precisely the same appearance described above. A complete chemical 

 analysis of this powder gives the following result : — 



Sulphate lime 62.590 



Silicate magnesia 9.305 



Chromate of lead 4.404 



Prussian blue 2.800 



Water 15.472 



Organic matter 3.270 



Oxide iron, alumina, with traces of copper and brass 2.159 



100.000 



thus confirming the conclusion arrived at from an examination of 

 many samples of glazed green tea, the bases of the bloom being gypsum, 



