CO2H  I~H2 HCOH 02H, while the natural xylose, which produces l-tartaric

acid by the substitution of CO2H for CHO.CHOH, corresponds to chloric, nitric, chloric, acetic, formic, sulphuric, oxalic, phosphoric, perchloric acids the specific rotation (calculated for the base) only varies from -272° to -288°; H . H . Landolt found the same thing for active acids, the mono lithium, sodium, potassium and ammonium tartrates varying only between 27.5° and 28.5° (calculated for the acid) . A corresponding rule may be expected where both base and acid have rotatory power; the molecular rotation will be the sum of those for base and acid in salts with inactive radicles .