=254. Methods Of Separation.=—The accurate determination of the quantities of the several optically active bodies formed in commercial glucose is not possible by any of the methods now known. Approximately accurate data may be secured by a large number of processes, and these are based chiefly on the ascertainment of the rotation and reducing power of the mixed sugars, the subsequent removal of the dextrose and maltose by fermentation or oxidation and the final polarization of the residue. The difficulties which attend these processes are alike in all cases. Fermentation may not entirely remove the reducing sugars or may act slightly on the dextrin. In like manner the oxidation of these sugars by metallic salts may not entirely decompose them, may leave an optically active residue, or may affect the optical activity of the residual dextrin. The quantitive methods of separating these sugars by means of phenylhydrazin, lead salts or earthy bases have not been developed into reliable and applicable laboratory processes. At the present time the analyst must be contented with processes confessedly imperfect, but which, with proper precautions, yield data which are nearly correct. The leading methods depending on fermentation and oxidation combined with polarimetric observations will be described in the subjoined paragraphs. =255. Fermentation Method.=—This process is based on the assumption that, under certain conditions, dextrose and maltose may be removed from a solution and the dextrin be left unchanged. In practice, approximately accurate results are obtained by this method, although the assumed conditions are not strictly realized. In the prosecution of this method the polarimetric reading of the mixed sugars is made, and the maltose and dextrose removed therefrom by fermentation with compressed yeast. The residual dextrins are determined by the polariscope on the assumption that their average gyrodynat is 193. In the calculation of the quantities of dextrose and maltose their gyrodynats are fixed at 53 and 138 respectively. The total quantity of reducing sugar is determined by the usual processes. The relative reducing powers of dextrose and maltose are represented by 100 and 62 respectively. The calculations are made by the following formulas:[210] _R_ = reducing sugars as dextrose _d_ = dextrose _m_ = maltose _dʹ_ = dextrin _P_ = total polarization (calculated as apparent gyrodynat) _Pʹ_ = rotation after fermentation (calculated as apparent gyrodynat). Whence _R_ = _d_ + 0.62_m_ (1) _P_ = 53_d_ + 138_m_ + 163_dʹ_ (2) _Pʹ_ = 193_dʹ_ (3) From these three equations the values of _d_, _m_, and _dʹ_ are readily calculated: _Example_: To find _d_ and _m_: