Oct. 10, 186-4.] 



♦ KNOAVLEDGE ♦ 



289 



MAGAZINE OF SCIENCE 



LONDON.- FRIDAY, OCT. 10, 1884. 



Contents op No. 154. 



FAGS 



TheChemi5lrv"of Cookery. XLIV'. 

 BvW. Mattieu Williams 2S9 



Flight of a Missile. {Itlus.) By 

 Eichard A. Proctor 290 



Emigrants' Prospects in Caumia. 

 {ConilmleJ.) By W. B. Browno 292 



The Entomology of a Pond. (litus.) 

 By E. A. Butler 29,') 



The International Health Exhibi- 

 tion. XIX. (/««..) 294 



Notes on Coal, By E. A. Proctor.. 295 



Dickens's Story Left Halt Told. 

 By Thomas Foster 297 



Electric Light Dangers. By W. Slingo 298 



PA6B 



New Stern-wheel Gunboats, {lllm.) 299 

 Other Worlds than Ours. By M. 

 de Fontenelle. With Notes by 



Richard A. Proctor 30O 



Tricycles in 18»4. By J. Browning 301 



Editorial Gossip 302 



Reviews 303 



Face of the Sky. By F.R.A.S 303 



Wolf a Comet 303 



Correspondence ; — The Afterglow 

 and its Cause — Life after Death — 



Brain Power, kc 301 



Our Whist Column 307 



Our ChoBS Column 308 



THE CHEMISTRY OF COOKERY. 



By W. Mattieu Williams. 



XLIV.— THE COOKERY OF WIXE {continued). 



THE paternal tenderness with which wine is regarded, 

 both by its producers and consumers, is amusing. 

 They speak of it as being " sick," describe its " diseases " 

 and their remedies as though it were a sentient being ; and 

 its diseases, like our own, are now attributed to bacilli, 

 bacteria, or other microbia. 



Pasteur, who has worked out this question of the origin 

 of diseases in wine as he is so well known to have done in 

 animals, recommends (in papers read before the French 

 Academy in May and August, 1865), that these microbia 

 be " killed " by filling the bottles close up to the cork, 

 which is thrust in just with sufficient firmness to allow the 

 wine on expanding to force it out a little, but not entirely, 

 thus preventing any air from entering the bottle. The 

 bottles are then placed in a chamber heated to temperatures 

 ranging from 4.-i" to 100° C. (113° to 212° Fahr.), where 

 they remain for an hour or two. They are then set aside, 

 allowed to cool, and the cork driven in. It is said that 

 this treatment kills the microbia, gives to the wine an in- 

 creased bouquet and improved colour — in fact, ages it con- 

 siderably. Both old and new wines may be thus treated. 



I simply state this on the authority of Pasteur, having 

 made no direct experiments or observations on these 

 diseases, which he describes as resulting in acetification, 

 ropiness, bitterness, and decay or decomposition. 



There is, however, another kind of sickness which I have 

 studied, both experimentally and theoretically. I refer to 

 the temporary sickness which sometimes occurs to rich 

 wines when they are moved from one cellar to another, and 

 to wines when newly exported from their native climate to 

 our own. The wines that are the most subject to such 

 sickness are those that are the most genuine — the natural, 

 unsophisticated wines, those that have not been subjected 

 to " fortification," to " vinage," to " plastering," " sulphur- 

 ing," &c. — processes of cookery to be presently described. 



This sickness shows itself by the wine becoming turbid, 

 or opalescent, then throwing down either a crust or a loose, 

 troublesome sediment. 



Those of my readers who are sufficiently interested in 

 this subject to care to study it practically should make the 

 following experiment : — 



Dissolve in distilled water, or, better, in water slightly 

 acidulated with hydrochloric acid, as much cream of 

 tartar as will saturate it. This is best done by heating 

 the water, agitating an excess of cream of tartar in it, then 

 allowing the water to cool, the excess of salt to subside, and 

 pouring off the clear solution. Kow 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 1 



It depends upon the fact that the bitartrate of potass, or 

 cream of tartar, is soluble to some extent in water, but 

 almost insoluble in alcohol. In a mixture of alcohol and 

 water its solubility is intermediate — the more alcohol the 

 smaller the quantity that can be held in solution (hydro- 

 chloric and most other acids, excepting tartaric, increase its 

 solubility in water). Thus, if we have a saturated solu- 

 tion of this salt either in pure water or acidulated water 

 or wine, the additioit of alcohol 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, containing saccharine and mucilaginous matter, 

 the precipitation takes place very slowly ; the particles 

 are excessively minute, and become entangled with the 

 mucilage, kc, 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 fermentation proceeds, and the sugar 

 of the grape-juice is converted into alcohol, the capacity of 

 the juice for holding the salt in solution dimini-shes, and it 

 is gradually thrown down. But it does not fall alone. It 

 carries with it some of the colouring and extractive matter 

 of the grape juice. This precipitate, in its crude state 

 called arrjol, or roher iceinstein, is the source from which 

 we obtain the tartaric acid of commerce, the cream of 

 tartar, and other salts of tartaric acid. 



Now let us suppose that we have a natural, un- 

 sophisticated 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 ex- 

 haustively fermented, 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 pre- 

 cipitation must occur. This precipitation will come down 

 very slowly, will consist not merely of pure crystals of 

 cream of tartar, but of minute particles carrying with it 

 some colouring matter, extractives, ifec, and thus spoiling 

 the brilliancy of the wine, making it more or less turbid. 



But this is not all. Boiling water dissolves a of its 

 weight of cream of tartar, cold water only ^a^, and, at 

 intermediate temperatures, intermediate quantities. There- 

 fore, if we lower the temperature of a saturated solution, 

 precipitation occurs. Hence, the sickening of wine due to 

 change of cellars or change of climate, even when no 

 further fermentation occurs. The lighter the wine, i.e., 

 the less alcohol it contains naturally, the more tartrate it 

 contains, and the greater the liability to this source of 

 sickness. 



This, then, is the temporary sickness to which I have 

 referred. I have proved the truth of this theory by 

 filtering such sickened wine through laboratory filtering 

 1 aper, thereby rendering it transparent, sind obtaining on 



