W. A. Davis 9 



basic lead acetate is allowed to act upon it. As the time increases the 

 solution becomes more and more yellow in colour but in no case does 

 a precipitation of laevulose become visible. The data given on pages 

 12-15 show that the sugar remaining in solution no longer consists 

 solely of laevulose. Not only does there appear to be a deficiency of 

 20 to 30 % of laevulose but values obtained for this sugar by reduction 

 are always far higher — 13 to 14 %^than the values calculated from 

 the rotatory power. This points to a substance being formed from the 

 laevulose which has a considerably lower reducing power than this 

 sugar and at the same time differing from it even more in rotatory 

 power. Such a substance is the so-called glutose, CgHjaOg, obtained 

 by Lobry de Bruyn and van Ekenstein^ on heating a 20 % solution 

 of laevulose with aqueous lead hydroxide at 70-100° ; it is described as 

 being nearly optically inactive and as having a reducing power about 

 one-half that of dextrose. It was found to be present in small quantities 

 in certain kinds of colonial molasses, being formed probably by the 

 action of alkali (lime) on the invert sugar during the processes of evapora- 

 tion in the factory^. 



The data given in the experimental part of this paper point to this 

 substance being formed at the ordinary temperature by the action of 

 basic lead acetate on dilute solutions of laevulose. The basic lead 

 acetate acts in fact in the same way as lead hydroxide itself. The 

 higher the temperature the more rapid is the disappearance of the 

 laevulose, so that heating a solution containing reducing sugars and 

 basic lead acetate should always be avoided. 



It is well known that Pellet advocates the use of normal lead acetate, 

 as suggested by Edson, in place of the basic salt, in clarifying liquors 

 which contain reducing sugars, so as to avoid the supposed precipitation 

 of laevulose. In most caseSj however, the normal acetate is far less 

 effective as a clarifying agent and it frequently leaves in solution 

 optically active substances, such as gums, which are completely elimi- 

 nated by the basic acetate and thus prevented from interfering with 

 the analysis. The writer's experience with many different kinds of 

 leaf material, rich in reducing sugars, would show that if the basic 

 lead acetate is added carefully in small quantities at a time until the 

 precipitation of the impurities is just complete^ and the actual excess 



1 Rec. Trav. Chim. 1897, 16, 262. 



2 PeUet, Bull. Assoc. Chim. 1899, 16, 1181 and 1902, 19, 8.34. 



' It is usually quite easy by testing small portions of the filtrate to hit off the point 

 at which this occurs to within 1 or 2 c.c, even when relatively large quantities (for example, 

 200 to 300 c.c.) of the basic lead solution have to be used. 



