972 TEA 



tartaric acid with powdered pumice-stono. The aqueous is separated from the oily 

 distillate by a wet filter, and evaporated at a gentle heat, till it commences to crystal- 

 lise. The crystals are digested in nitric acid, and thus the pure pyrotartaric acid is 

 obtained. 



TARTXATSS are bibasic salts, composed of tartaric acid and oxidised bases, in 

 equivalent proportions. Some of the tartrates are employed in the arts, bitartrate of 

 potash being used as a mordant in dyeing -woollen fabrics. Tartrate of chromium is 

 sometimes used in calico-printing, and the tartrate of potash and tin in wool-dyeing. 



TASMANTTE. A combustible mineral found in Tasmania. See DTSODILB. 



TAWING is the process of preparing the white skins of the sheep, doe, &c. See 

 LEATHER. 



TEA (The, Fr. ; TJiee, Ger.) Thea, the tea-plant, belongs to the natural order 

 Ternstromiacea. Considerable discussion has taken place with reference to this im- 

 portant substance, some contending that green and black tea are the productions of 

 two different plants, the Thea viridis producing the green tea, and the Thea Bohea the 

 black tea. There is a third variety, the Thea Assamensis, or Assam tea, which appears 

 to resemble both the others. Mr. Fortune appears to have proved that the green and 

 black teas of commerce do not depend upon specific differences ; but that in the northern 

 tea districts of China the black, and green teas are both obtained from the same species 

 or variety, namely, the Thea viridis, while in the Canton tea districts both the varieties 

 of tea are made from the Thea Bohea. 



The quality of the tea depends much on the season when the leaves are picked, 

 the mode in which it is prepared, as well as on the district in which it grows. 

 Green tea, it is stated, is coloured by the application of an extract of indigo, of 

 Prussian blue, and gypsum ; and that the fine odour which renders the ' flowery ' 

 kinds remarkable is derived from the leaves of Oka fragrans, a species of camellia, 

 and other similar plants. 



To the black tea belong the varieties known as Bohea, Congou, Campoi, Souchong, 

 Caper, and Pekoe. To the green tea, Twankay, Hyson-skin, Hyson, Imperial, and 

 Gunpowder. 



Brande, in his 'Manual of Pharmacy,' has given a table from which the following 

 facts are extracted : 



Soluble Soluble Precipitated Insoluble 



100 parts of Tea in water in alcohol by jelly residue 



Green Hyson Best . 41 44 31 56 



Medium. 34 43 26 58 



Lowest . 31 41 24 57 



Black Souchong Best . 35 36 28 64 



Medium. 37 35 28 63 



Lowest . 35 31 23 65 



The most remarkable products in tea are 1st* Tannin. 2nd. An essential oil 

 to which it owes its aroma, and which has great influence on its commercial value. 

 3rd. A crystalline substance, very rich in nitrogen, theine, which is also met with in 

 coffee (whence it is frequently termed caffeine). 



Besides these three, M. Mulder extracted from tea eleven other substances, which 

 are usually met with in all leaves. The same chemist found, in the various kinds of 

 tea from China and Java, a little less than a half per cent, of their weight of theine. 

 Dr. Stenhouse obtained from 1-36 to - 98 theine from 100 parts of tea. On deter- 

 mining the nitrogen by M. Dumas's process, he obtained the following numbers : 



Nitrogen in 100 parts 

 tea dried at 230 



Pekoe tea . 5'58 



Gunpowder tea . . , 6'15 



Souchong tea . . . . . . . . 6' 15 



Assam tea , 5'10 



This amount of nitrogen is far more considerable than has been detected in any 

 vegetable hitherto analysed. 



The proportion of products soluble in hot water varies considerably, and depends 

 chiefly upon the age of the leaf, which is younger, and consequently less liqueous. in 

 the green than in the black tea. On an average, Stenhouse found in 100 parts 



Farts soluble in 

 boiling water. 

 Dry black teas ........ 43-2 



Dry green teas 47' 1 



Black teas in their commercial state .... 38'4 

 Green teas do. do. . . 43*4 



