_Maltosazone._—This substance melts at 206° with decomposition. It is left rotating. Its structure is represented by the formula C₂₄H₃₂N₄O₉. _Galactosazone._—This substance, C₁₈H₂₂N₄O₄, has the same centesimal composition as the corresponding bodies produced from dextrose and levulose. It is distinguished from these compounds, however, by its low melting point, _viz._, 193°. The above comprise all the phenylosazones which are important from the present point of view. Sucrose, by inversion, furnishes a mixture of dextros- and levulosazones when treated with phenylhydrazin, while starch and dextrin yield the dextros- or maltosazone when hydrolyzed. Lactose yields a mixture of dextros- and galactosazones when hydrolyzed and treated as above described. The reactions with phenylhydrazin are approximately quantitive and it is possible that methods of exact determination may be based on them in the near future.[138] =173. Other Qualitive Tests for Sugars.=—The analyst may sometimes desire a more extended test of qualitive reactions than those given above. The changes of color noticed on heating with alkalies may often be of advantage in discriminating between different sugars. The formation of definite compounds with the earthy and other mineral bases may also be used for qualitive determinations. One of the most delicate qualitive tests is found in the production of furfurol and this will be described in the following paragraphs. =174. Detection of Sugars and Other Carbohydrates by Means of Furfurol.=—The production of furfurol (furfuraldehyd) as noted in paragraph =150=, is also used quantitively for the determination of pentose sugars and pentosans. Furfurol was first obtained from bran (_furfur_), whence its name, by treating this substance with sulfuric acid, diluted with three volumes of water, and subjecting the mixture to distillation. Its percentage composition is represented by the symbol C₅H₄O₂, and its characteristics as an aldehyd by the molecular structure C₄H₃O,C-HO. Carbohydrates in general, when treated as described above for bran, yield furfurol, but only in a moderate quantity, with the exception of the pentoses. Mylius has shown[139] that Pettenkofer’s reaction for choleic acid is due to the furfurol arising from the cane sugar employed, which, with the gall acid, produces the beautiful red-blue colors characteristic of the reaction. Von Udránszky[140] describes methods for detecting traces of carbohydrates by the furfurol reaction, which admit of extreme delicacy. The solution of furfurol in water, at first proposed by Mylius, is to be used and it should not contain more than two and two-tenths per cent, while a solution containing five-tenths per cent furfurol is found to be most convenient. The furfurol, before using, should be purified by distillation, and, as a rule, only a single drop of the solution used for the color reaction.