Objective: To investigate the in vivo and in vitro effects of black tea on the oxidative modi®cation of low density lipoprotein (LDL). Design: The antioxidant activity of the tea was studied in vitro by measuring the resistance of the LDL to oxidative modi®cation in the presence of copper. The effects of tea consumption in vivo were investigated in two settings. Firstly, to assess the acute effects of tea consumption, ®ve fasting healthy subjects ingested 600 mls (50.7 AE 5.4 mg¯avonoids) of black tea and peripheral venous blood was collected at 0, 30, 60, 90, 120 and 180 min after consumption. Secondly, to assess the effects of chronic tea consumption, a randomised crossover trial of tea (126.8 AE 13.5 mg¯avonoids) and coffee consumption was carried out in ten healthy subjects. Results: Black tea extract increased the resistance of LDL in vitro in a concentration dependent manner. There was no signi®cant change in total plasma antioxidant capacity or susceptibility of the LDL to oxidation over the 3 h period after consumption of black tea. The four-week crossover study in which coffee was used as a control against the black tea showed no signi®cant difference in the total plasma antioxidant capacity or susceptibility of LDL to oxidation between the tea and coffee groups. Serum lipids, including total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol did not change signi®cantly throughout the study. Conclusions: The consumption of moderate quantities of black tea acutely or for one week does not increase plasma total antioxidant capacity or alter the susceptibility of LDL to oxidation. Sponsorship: This work was funded by the Department of Agriculture for Northern Ireland.

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This paper presents briefly the results obtained in a study of the vapor pressures of aqueous solutions of sodium nitrate and potassium thiocyanate at 25°C. The apparatus and the technique are the same as that employed in our previous work (3, 2).Large samples of the "analyzed" salts were further purified by recrystallization, twice from distilled water and once from conductivity water. All solutions were made up on a weight molal basis. Solutions of sodium nitrate were made by direct weighing of the dry salt, previously heated to constant weight at 140°C. The saturated solution was prepared by first filling the saturators with a solution of the salt saturated at a temperature a few degrees higher than the temperature of the bath. The saturators were then transferred to the constant-temperature thermostat and the electrolytic gas was allowed to pass for two days while the solution was coming to equilibrium with the solid crystals at 25°C. ± 0.005°.Concentrated stock solutions of the thiocyanate were prepared and stored in glass-stoppered, mercury-sealed flasks in the dark. The thiocyanate content of each was determined gravimetrically as silver thiocyanate. The experimental solutions were made by diluting definite weights of these solutions to the desired molality. The densities, df°°, are the mean of at least three determinations and are accurate to 1 part in 300,000.The final experimental and calculated data are collected in tables 1 and 2. In these m is the molality of the salt solution, c is the molarity, and Pi is the vapor pressure of the solvent. Each value of pi is the mean of at

lowing adsorbents have been used: two copper catalysts, glaucosil, pumice, nickel oxide supported on pumice, nickel on pumice, dry powdered bacteria, chromic oxide gel, "glowed" chromic oxide, potassium chloride, copper sul-fate pentahydrate, anhydrous copper sulfate, two silica gel samples, activated charcoal, and two Darco samples (activated carbons). All adsorbents except charcoal gave S-shaped isotherms, and the values for the surface area evaluated from the different isotherms for the same adsorbent were consistent with each other.

The variation of the classical dissociation constant of acetic acid with changing molecular acetic acid concentration in solutions 0.1 molar in sodium acetate and 0.9 molar in potassium or sodium chloride has been determined using the quinhydrone electrode. The stability of acetic acidacetate buffers has been investigated.