REFRACTIVE INDICES, SPECIFIC GRAVITIES, AND SOLUTION FACTORS OF SOLUTIONS OF THE SOLIDS OF WORT, COLD-WATER EXTRACT AND BEER

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Abstract
For such solutions of mixed solutes as worts and beers, only an approximate general relationship can be established between either the refractive index or the specific gravity of the solution and the total amount of solute; consequently, arbitrary factors or tabulated figures based on pure solutes are in common use. Freeze-drying offered a means of preparing the solids from typical worts and beers in a dry and unaltered form, and, by using these solids, of establishing directly in a limited number of cases the relationships between physical characters and concentrations of solutions. From the consolidated results solution factors have been calculated, and the concentrations which they indicate for the materials now examined have been compared with those obtained from the Plato Table and the Zeiss Immersion Re-fractometer Table for sucrose. It is shown that the use of these tables leads in the present cases, and probably more generally, to overestimation of the amounts of substance in solution. Similarly, the solution factor 3·86, used in the Institute of Brewing standard method for the determination of cold-water extract, has given high results, and more accurate figures, over the range of gravities encountered for this determination in average malts, were obtained from the factor 3·93. Methods are described for determining temperature corrections for the specific gravities of laboratory worts, cold-water extract filtrates, and solutions of beer solids.

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