2. That the presence of potassium sulphate in the wines of commerce, which results from, plastering the must, from the mixture of plaster or sulphuric acid with the wine, or from cutting with plastered wines, should only be tolerated to the maximum limit of 2 grammes per litre (about 117 grains per gallon).
In calling my attention to this notice, my colleague of agriculture and commerce informs me that he completely concurs.
He, therefore, instructs the officers to prosecute, under the laws against adulterations, the dealers who shall sell wine containing more than the quantity indicated of potassium sulphate, as dangerous to the health of the consumers.
Plastering Sherry—Quantity Used.—Mr. Vizitelli says that during his stay at Jerez, he paid particular attention to the plastering question, saw the gypsum applied in almost a hundred instances, and questioned the overseers in scores of vineyards. He states that within his own knowledge gypsum is by no means invariably used in the vinification of sherry, as already stated under the head of Sherry. And although applied in the majority of cases, but a few pounds per butt are used, say 6 lbs. at most in a dry season, and a little more than double that quantity in years when great dampness prevails. And he argues from the Montpellier experiment, already mentioned, where the committee added 40 grammes of gypsum to a litre of wine, and found only 1.240 grammes of sulphate of potash per litre where pure calcium sulphate was used, and 1.828 grammes where ordinary plaster was employed, that when the Spaniards add the amount which they do to the must in sherry making, no injury to the wine can occur. It may be proper to suggest, however, for the benefit of future inquirers, that wine, after insensible fermentation, contains but a small proportion of the potassium bitartrate which was contained in the grape, the greater part of it having been deposited with the lees and the marc. Wines do not contain tartar enough to furnish 2 grammes per litre of potassium sulphate, nor enough to act upon 1 gramme of pure gypsum. But it is far otherwise with grape juice. Now 6 lbs. of gypsum to one butt of wine of 108 Imperial gallons would be the same as about 5.5 grammes per litre, and if pure, ought to produce, on being fully satisfied with the acid potassium tartrate, as much as 8 grammes per litre of potassium sulphate, and Mr. Carles, above quoted, says that it does amount to from 4 to 7.5 grammes per litre in plastered wines.
Supposing the following to be the correct reaction, 1 gramme of pure gypsum ought to produce, with 2.6 grammes of cream of tartar, 1.477 grammes of sulphate of potash; and to produce the 2 grammes per litre of the latter would only require 1.353 of the former; and but a little more than 1 lb. of pure gypsum could safely be added to 100 gallons of must:
CaSO₄ + 2(C₄H₅KO₆) = C₄H₄CaO₆ + C₄H₆O₆ + K₂SO₄
As the gypsum is usually added to the pomace itself, or to the grapes before crushing, it is unsafe to argue from the effects produced by adding it to wine.
By Adding Water to must, the effects of plastering may be produced, if the water is hard by reason of the gypsum contained in it.
SHERRY FLAVOR.
In many California wines a flavor called the “sherry flavor” is often observed; and in the red wines may frequently be tasted what would with equal propriety be called a “port flavor;” and the “sherry flavor” would by some be called a “Madeira flavor.”