THE ESTIMATION OF CARBOHYDRATES. V. 



THE SUPPOSED PRECIPITATION OF REDUCING SUGARS 

 BY BASIC LEAD ACETATE. 



By WILLIAM A. DAVIS 

 {Rothamsted Experimental Station). 



GiLL^ in 1871 first pointed out that when an excess of basic lead 

 acetate is added to a solution of invert sugar the negative rotation of 

 the latter is greatly reduced owing to the formation of a soluble lead 

 compound of laevulose. If sufficient lead solution is added the negative 

 rotation may become a positive one; thus in one experiment quoted 

 by Gill a negative reading of — 28° was transformed into a positive 

 value of + 57°. The change of rotation was not, however, permanent 

 and on removing the lead or on acidifying the solution the original 

 rotatory power was restored. The change of rotation was attributed 

 to an effect of the lead on the laevulose only; a solution of dextrose 

 was practically unaffected by the presence of basic lead acetate. Since 

 Gill's paper the effect of basic lead acetate as a source of error in sugar 

 analysis has been the subject of numerous papers especially by Pellet^, 

 Svoboda^, Edson*, Prinsen Geerligs^, Watts and Tempany^ and Eynon'^. 



As a result of this work the belief has grown up that when laevulose 

 is present in a sugar solution which is defecated by basic lead acetate, 

 a portion, if not the whole, of the laevulose is thrown down in the 



1 Trmis. Chem. Soc. 1871, 24, 91. 



2 Bull. Assoc. Chim. Sucr. 1891, 9, 439; 1896, 14, 28 and 1.31; 1897, 15, 605; 1899, 

 16, 1007 and 1147; 1900, 17, 52; 1904, 22, 744; 1913, 31, 205; 1914, 32, 909. 

 J. Fabr. Sucr. 1899, 40, No. 15. Sucrerie Indigene, 1904, 64, 67. 



3 Zeit. Ver. Rubenzuckerind. 1896, 46, 107. 



« Bull. Assoc. Chim. Sucr. 1890, 8, 323; 1891, 9, 552. 



5 Archiv Zuckerind. Javas, 6, 914; Zeit. Ver. Deut. Zuckerind. 1908, 932; Int. 

 Sugar J. 1908, 10, 432. 



« J. Soc. Chem. Ind. 1908, 27, 53. 



7 1th Int. Congress App. Chem. 1909, 5, 193. 



