The Chemistry of Cookery

late Emperor Napoleon III. drank dry sherry, and was a martyr of this kind. I repeat emphatically that, generally speaking, high-priced dry sherries are far worse than cheap Marsala, both as regards the quantity they contain of sulphates and free acid. Anybody who doubts this may convince himself by simply purchasing a little chloride of barium, dissolving it in distilled water, and adding to the sample of wine to be tested a few drops of this solution. Pure wine, containing its full supply of natural tartrate, will become cloudy to a small extent, and gradually. A small precipitate will be formed by the tartrate. The wine that contains either free sulphuric acid or any of its compounds will yield _immediately_ a copious white precipitate like chalk, but much more dense. This is sulphate of baryta. The experiment may be made in a common wine-glass, but better in a cylindrical test-tube, as, by using in this a fixed quantity in each experiment, a rough notion of the relative quantity of sulphate may be formed by the depth of the white layer after all has come down. To determine this _accurately_, the wine, after applying the test, should be filtered through proper filtering paper, and the precipitate and paper burnt in a platinum or porcelain crucible and then weighed; but this demands apparatus not always available, and some technical skill. The simple demonstration of the copious precipitation is instructive, and those of my readers who are practical chemists, but have not yet applied this test to such wines, will be astonished, as I was, at the amount of precipitation. I may add that my first experience was upon a sample of dry sherry, brought to me by a friend who bought his wine of a respectable wine-merchant, and paid a high price for it, but found that it disagreed with him; it contained an alarming quantity of free sulphuric acid. Since that I have tested scores of samples, some of the finest in the market, sent to me by a conscientious importer as the best he could obtain, and these contained sulphate