520 THE POPULAR SCIENCE MONTHLY. 



Pure wine, containing its full supply of natural tartrate, will be- 

 come 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 copi- 

 ous white precipitate like chalk, but much more dense. This is sul- 

 phate of baryta. The exjDeriment 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 apply- 

 ing the test, should be filtered through proper filtering-paper, and the 

 precipitate and paper burned in a platinum or porcelain crucible and 

 then weighed ; but this demands apparatus not alwaj^s available, and 

 some technical skill. The simple demonstration of the copious pre- 

 cipitation is instructive, and those of my readers who are practical 

 chemists, but have not yet applied this test to such wines, will be as- 

 tonished, 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 most respectable 

 wine-merchant, and paid a high price for it, but found that it disa- 

 greed with him ; since that I have tested scores of samples, some of 

 the finest in the market, sent to me by a thoroughly conscientious im- 

 porter as the best he could obtain, and these contained sulphate of 

 potash instead of bitartrate. 



My friend, the sherry-merchant, could not account for it, though 

 he was most anxious to do so. This was about three years ago. By 

 dint of inquiry and cross-examination of experts in the wine-trade, I 

 have, I believe, discovered the origin of the sulphate of potash that is 

 contained in the samples that the British wine-merchant sells as he 

 buys, and conscientiously believes to be pure. I will state jDarticulars 

 in my next. 



XLV, — COCOA AND THE COOKERY OF WINE. 



A correspondent writes to the editor asking whether I class co- 

 coa among the stimulants. So far as I am able to learn, it should 

 not be so classed, but I can not speak absolutely. Mere chemistry 

 supplies no answer to this question. It is purely a physiological sub- 

 ject, to be studied by observation of effects. Such observations may 

 be made by anybody whose system has not become " tolerant " of the 

 substance in question. My own experience of cocoa in all its forms is 

 that it is not stimulating in any sensible degree. I have acquired no 

 habit of using it, and yet I can enjoy a rich cup or bowl of cocoa or 

 chocolate just before bed-time without losing any sleep. When I am 

 occasionally betrayed into taking a late cup of coffee or tea, I repent 

 it for some hours after going to bed. My inquiries among other peo- 

 ple, who are not under the influence of that most powerful of all argu- 

 ments, the logic of inclination, have confirmed my own experience. 



