I n t he prese nt investigation, the cha nges in the equilibrium specifi c r otation ca used by t he addi tion of either sodium or potassiu m tetr aborate to solu t ions of D-glucose, D-fru ctose, L-sorbosc, s ucrose, mannitol, a nd sorbi tol have bee n obser ved a nd t he results in tc rpret ed . Measure ments h ave been m ade fo r various conce ntra tions of carbohydrat es with fi xed co nce nt rations of borat c, and for vari ous conce ntr ations of borate wit h fi xcd co nce ntr atio ns of carboh ydratc. It was t hus possible to obser ve independently t he effcct of variatio n in t he co ncentration of eit her carboh ydrate or bor ate. The resul ts indi cate t h at glucose, fru ctose, sor bose, a nd sorbitol for m t hree b orate co mpounds, t hat m a nnitol forms two, a nd s ucr ose one. T he optical rotations of the compo unds ha ve bee n estimaLed, a nd t he co mposition of t hc solutions disc ussed . Exte nsive ta bles have been i nclud ed, givin g t he op tical r otations of t he above-me ntio ned carbohydrates i n the pr esence of sodium a nd potassiu m tet raborat e.