Analytical Determination of Tartrate Stability in Wine. I. Potassium Bitartrate

¹ Departments of Viticulture and Enology, and Chemistry University of California, Davis

The first and second dissociation constants of tartaric acid were determined in alcohol, and the ratio of the two constants found to be different than in water. Solubility product constants for KHT at the average ion strength of wine were calculated over the range of alcohol content and temperatures of interest to enologists.

The effect of the ionic strength of wine on the activities of HT^- and T⁼ ions was included in the calculations of the dissociation constants of tartaric acid in wine. Tables giving the variation in percent HT with pH for table and dessert wines were prepared by calculations using these dissociation constants.

Graphs are presented showing that the precipitation rate of KHT from wine is a great deal less than from alcohol-water solutions. Certain solubility product values of KHT are tentatively suggested as stability levels for various types of wine. Possible reasons are offered for the differences in solubility of KHT in wine and alcohol.

An analytical procedure is offered to determine KHT stability in wine. Because data are insufficient, if can presently be used only as a tentative procedure. It is suggested that a cooperative effort be made to acquire sufficient data to establish this analytical determination as a reliable procedure for measuring the degree of potassium bitartrate stability in wine.