The specific gravities of systems of furfural and toluene are practically a linear function of composition, hence the percent of furfural in toluene can be readily analyzed by a determination of the specific gravity of the system;A technique has been developed for the preparation of furfural from strong solutions of xylose. The xylose solution with the dehydrating agent in solution is refluxed with an immiscible solvent, for example with toluene, and the yield of furfural estimated from the specific gravity of the solvent-furfural system;Detailed studies were made of the yield of furfural from xylose using as the dehydrating agent various mixtures of HCl and NaCl for varying periods of time;The NaCl markedly increases the yield of furfural in the presence of a given concentration of HCl. This increase is quantitatively correlated with the effect of the NaCl upon the activity of the acid and of the furfural. The latter two factors were determined in terms of the effect of the salt upon the "apparent" hydrogen ion concentration and upon the solubility of furfural in the aqueous phase.