The ionization constants of methyl-, ethyl-and phenylmercuric hydroxides and of methylmercuric chloride and bromide have been measured by potentiometric titration. All are weak electrolytes. The solubility products of methyl-and phenylmercuric halides have been found, partly potentiometrically and partly by direct solubility measurements. A convenient way of titrating alkyl mercuric hydroxides is described, and evidence is given to show that a certain method for preparing solid methyl mercuric hydroxide actually leads to the oxide.(1) Most of this work is taken from the Ph.D. thesis of Thomas D.
Many laboratory manuals include lengthy schemes for extraction of caffeine from tea.1 A time-saving experiment using No-I)oz tablets as the source has recently been described in this Journal.2 However, soft drinks derived from the kola bean, and some that are not, also contain caffeine that can be isolated and purified in as little as 1 hr.In some of the soft drinks that we studied, simple extraction with chlorinated solvents yielded caffeine that was contaminated by relatively large amounts of benzoic acid. Showing a strong pl\ dependence (caffeine does not: Ka < 10-14; Kb < 10-14), benzoic acid can easily be held in the aqueous phase, but it. may be extracted and isolated as a second product. In such beverages as Coca-Cola, Pepsi Cola, Royal Crown Cola, Dr. Pepper, Mountain Dew, Orchard Park Cola (a local brand), and the low-sugar and sugar-free versions of several of these, we found that a 12-oz.can contained 25-50 mg of caffeine. Half a can is therefore sufficient for students either to see the crude product, to
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