Studies on Fluorine Content in Tea

Abstract

Fluorine content of several organs of tea plant (bud, young leaf, mature leaf, stem and root) was determined by the colorimetric method with thorium-neothrin. The effect of supplying sodium fluorine on the fluorine content of tea leaf, and the extracting rate of fluorine from tea with water and organic solvents were also investigated.It was found that the fluorine content of tea leaf increased about 2-6 times by supplying sodium fluoride in both pot and field culture and fertilizing superphosphates also increased the content, in comparison with inorganic nitrogenous fertilizers.All parts of tea plant contained some quantity of fluorine and especially. the mature leaf contained the most of all. No significant difference of the content was observed between the stem and the root.Upon standing for 24 hours at room temperature, fluorine in tea was extracted about 60-80%, 50-60% and 40-50% of the total with hot water, ethanol and ethyl ether, respectively.Instant tea, made from fluorine-enriched tea leaves by feeding with sodium fluoride, contained 150-500 p.p. m. of fluorine.