5i8 THE POPULAR SCIENCE MONTHLY. 



subside, and pouring off the clear solution. Now add to this solution, 

 while quite clear and bright, a little clear brandy, whisky, or other 

 spirit, and mix them by shaking. The solution will become " sick," 

 like the wine. Why is this ? 



It depends ujjon the fact that the bitartrate of potash, or cream of 

 tartar, is soluble to some extent in water, but almost insoluble in alco- 

 hol. In a mixture of alcohol-and-water its solubility is intermediate 

 — the more alcohol the smaller the quantity that can be held in solution 

 (hydrochloric and most other acids, excepting tartaric, increase its 

 eolubility in water). Thus, if we have a saturated solution of this salt 

 either in pure water or acidulated water or wine, the addition of alco- 

 hol throws some of it down in solid form, and this makes the solution 

 sick, or turbid. "When pure water or acidulated water is used, as in 

 the above-described experiment, crystals of the salt are freely formed, 

 and fall down readily ; but with a complex liquid like wine, contain- 

 ing saccharine and mucilaginous matter, the precipitation takes place 

 very slowly ; the particles are excessively minute, and become entan- 

 gled with the mucilage, etc., and thus remain suspended for a long 

 time, maintaining the turbidity accordingly. 



Now, this bitartrate of potash is the characteristic natural salt of 

 the grape, and its unfermented juice is saturated with it. As fermenta- 

 tion proceeds, and the sugar of the grape-juice is converted into alco- 

 hol, the capacity of the juice for holding the salt in solution dimin- 

 ishes, and it is gradually thrown down. But it docs not fall alone. 

 It carries with it some of the coloring and extractive matter of the 

 grape-juice. This precipitate, in its crude state called argol, or roher 

 Wemstein, is the source from which we obtain the tartaric acid of com- 

 merce, the cream of tartar, and other salts of tartaric acid. 



Now let us suppose that we have a natural, unsophisticated wine. 

 It is evident that it is saturated with the tartrate, since only so much 

 argol was thrown down during fermentation as it was unable to retain. 

 It is further evident that if such a wine has not been exhaustively fer- 

 mented, i. e., still contains some of the original grape-sugar, and, if 

 any further fermentation of this sugar takes place, the capacity of the 

 mixture for holding the tartrate in solution becomes diminished, and 

 a further precipitation must occur. This precipitation will come down 

 very slowly, will consist not merely of pure crystals of cream of tar- 

 tar, but of minute particles carrying with it some coloring-matter, ex- 

 tractives, etc., and thus spoiling the brilliancy of the wine, making it 

 more or less turbid. 



But this is not all. Boiling water dissolves ^ of its weight of cream 

 of tartar, cold water only y^, and, at intermediate temperatures, inter- 

 mediate quantities. Therefore, if we lower the temperature of a satu- 

 rated solution, precipitation occurs. Hence, the sickening of wine due 

 to change of cellars or change of climate, even when no further fer- 

 mentation occurs. The lighter the wine, i. e., the less alcohol it con- 



