992
WINE.—Ethers.
inodorous oil, soluble in alcohol and ether, butinsoluble in water. It has a feeble acid reaction,and is readily soluble in caustic alkalies and alkalinecarbonates, with formation of the salts of thesebases. The acid is dibasic, and forms two kindsof salts, acid and neutral. When distilled by itselfit breaks up into water and amanthic anhydride,C u U 2i 0 2 ■ the latter boils at 260°, but decomposesin part, so that the boiling-point rises to 293° ; thedistillate becomes solid at 31° C.
Estimation of the Quantity of Acids in Wins. —Thevolatile acids may be conveniently estimated as aceticacid; the fixed acids may be estimated as if theywere malic and tartaric only. The total saturatingpower is determined in 20 c.c. of wine by a standardsolution of caustic soda of decinormal strength,logwood tincture being used as the indicator.Another 20 c.c. are then evaporated to dryness andheated for half an hour, until all volatile acid hasbeen driven off, and the loss of water is restored.In this fluid the amount of fixed acid is nowestimated; it represents the total free fixed acid ofthe wine, and the difference between this and thefirst estimation gives the total volatile acids present,as measured by their neutralizing power. The freevolatile acid cannot be determined by distillation, asit does not completely pass over.
In good sound wines the total amount of freeacid ranges from 0'3 to 0-7 per cent.; wines withmore than the latter amount of free acid are neitherpleasant nor wholesome. Of the total acidity notmore than about 015 per cent, should be due tovolatile acid.
Estimation of Tartaric Acid and Bitartrate of Potashin Wine . —The bitartrate of potash is slightly solublein water, and insoluble in strong alcohol or a mixtureof alcohol and ether. Upon this insolubility themethods for the estimation of tartaric acid and bitar-trate have been based. According to Bertiielot,20 c.c. of wine are mixed in a stoppered bottle with100 c.c. of a mixture of equal volumes of alcoholand ether; to another 20 c.c. of the wine a quantityof potash (sufficient to neutralize about one-fifth ofthe free acid of the wine) is added, together with100 c.c. of the ether and alcohol mixture. Bothbottles are then set aside for three days in a coolplace; at the end of this time almost all the bitar-trate of potash present in both bottles will havebeen deposited, sometimes in defined crystals. Theseprecipitates are then collected on filters, washed withalcohol ether introduced with the paper into a flaskeach, and dissolved in distilled water, if necessarywith the aid of heat. The free acid present in thesesolutions is then estimated by a decinormal solutionof soda, with logwood as indicator.
The ether - alcohol retains only O'OOI gram, ofbitartrate in solution; these have to be added tothe quantities found. With this correction, theprecipitate from the first 20 c.c. represents thebitartrate present in the wine; the precipitate fromthe second 20 c.c. contains the whole amount oftartaric acid present. In order to obtain the per-centage of bitartrate and of tartaric acid in the wine,
multiply the number of c.c. of decinormal sodarequired to neutralize the precipitates, plus thenecessary correction of 0-21 c.c. for the bitartrateremaining in solution, by 0'094 and0'075 respectively.The method of Nessler is similar to, but lessaccurate than the one described.
In the majority of wines all the tartaric is presentas bitartrate; that is to say, there is a sufficientamount of potash present to enable the whole ofthe tartaric acid to be precipitated in this form byether-alcohol. The wines, in fact, frequently repre-sent a solution of bitartrate, saturated at the lowesttemperature to which the wine may have beenexposed.
All pure natural wine contains more or less oftartaric acid, and the quantity is probably the higherthe riper were the grapes from which it wasproduced. There is not, however, any apparentconnection between the amount of tartaric acidpresent and the quality of the wine. On the otherhand, strongly fortified wines contain little or notartaric acid, and this acid is almost entirely absentfrom all wines during the production of whichplaster of Paris has been employed.
The amount of tartaric acid in wine is only afraction of the entire amount of free fixed acidpresent in it; the greater part of the free fixed acidconsists of malic acid. This can be determined byadding to, say 50 c.c. of wine, limewater as long asa precipitate is produced; this being filtered off, thefiltrate is evaporated to 25 c.c., and mixed with muchabsolute alcohol. Malate and sulphate of calciumare precipitated, collected, dried, and weighed. Thesulphate of calcium is then estimated and deductedfrom the total, leaving the malate of calcium. Theother organic acids contained in wine cannot atpresent be estimated quantitatively with any degreeof exactness.
Vinous Ethers. —By far the greater part of thevolatile ethers found in wine is aceto-ethylic ether,<WCA)O s , ' y hi°h being volatile, and possessinga very decided smell, doubtless contributes much tothe general flavour of the wine; but neither thecharacteristic wine-flavour nor the peculiar bouquetof wines is due to it. In wine the ether is formedby the action of acetic acid on alcohol, perhapsfacilitated by the presence of other acids, but keptwithin certain limits by the presence of water. Asthe formation of a compound ether under theseconditions takes place gradually, the amount of itpresent at a given time is, to a certain extent, ameasure of the age of the wine. Besides aceticether minute quantities of ethyl-compounds of thehigher acids of the fatty series are present in wine,and contribute to its flavour.
(Enantkic Ether, C 18 II 3(i 0 3 . Towards the endof the distillation of wine (or wine-yeast) an oilyliquid passes over in small quantity, 40,000 partsof wine yielding about 1 part of the oil. This oilis oenanthic ether mixed with a variable proportionof acid. To obtain the pure ether this crude oil isagain distilled, and the first quarter coming overis separated. This is agitated and heated with a