Brix very similarly to sucrose with respect to specific gravity as a function of concentration, or compounds which are present in small amounts (minerals, hop acids in wort, tannins, acids in must). In any case, even if °Bx are not representative of the exact amount of sugar in a must or fruit juice they can be used for comparison of relative sugar content. As specific gravity was the basis for the Balling, Brix and Plato tables, dissolved sugar content was originally estimated by measurement of specific gravity using a hydrometer or pycnometer. In modern times, hydrometers are still widely used, but
Wine Grapes franc may have originated in Basque country of Spain. Additionally the origins of the assumed to be French varieties of Mourvèdre, Grenache and Carignan are shown to likely be Spanish instead. Another detail revealed by DNA testing and reported in "Wine Grapes" is that several northern Italian white wine grape varieties including Favorita, Pigato and Vermentino are genetically the same grape vine which is known under the synonym of "Rolle" in France but has no genetic relationship to the Rollo grape of Liguria. A number of grape varieties are illustrated by reproductions of colour plates from "Ampélographie. Traité général de