12 



The Estimation of CarJjohy (hates 



Experimental. 



A. Laevulose ex])erimenis. 



Series I. Solution 1. An approximately 1 % solution of Kahl- 

 baum's pure laevulose from inulin was prepared. Under Brown, 

 Morris and Millar's conditions^ 



20C.C. gave (1) 0-4528 grm. CuO 

 (2) 0-4o21 

 Average = 0-4525 grm. CuO = 0-2047 grm. laevulose. 



The concentration of the laevulose solution is therefore 1*0235 grms. 

 per 100 c.c. In a 400 ram. tube the rotation observed was — 3-663° 

 at 20° (sodium flame). 



Expt. 1. Basic lead acetate precipitated with sodium carbonate imme- 

 diately after hei?ig added to the laevulose solution. 



50 c.c. of solution 1 (= 0-5117 grm. laevulose) were mixed with 

 5 c.c. of basic lead acetate (sp. gr. 1-25, prepared according to Allen's 

 Commercial Organic Analysis, i. 308) ; powdered sodium carbonate was 

 then added, little by little, until the whole of the lead was just preci- 

 pitated. A very slight excess of the carbonate was used, so that the 

 solution was just faintly alkaline. The solution was diluted to 100 c.c. 

 at 15° and the rotatory and reducing powers were determined. The 

 values given are the mean of two or more separate experiments. 



Table I. 



Reduction 



Polarisation 



CuO 

 from 25 c.c. 



grms. 



0-2930 



Laevulose 



calculated per 



100 c.c. soln. 1 



grms. 



1010 



% of 

 laevulose 



a2" in 



I) 



400 mm. 

 tube 



- 1-840° 



Laevulose remaining 



calculated from 



rotation 



/o 



100-5 



rcmaming 

 99-3 



Thus practically 100 % of the laevulose present is found after the 

 treatment with basic lead acetate and sodium carbonate. The reduction 

 result is a trifle low and the polarisation value a trifle high, but the 

 differences are within the limits of experimental error; the average 

 of the two methods is 99-9 %. 



Expt. 2. Basic lead acetate precipitated immediately hy sodium 

 sulphate. 



5 grms. of sodium sulphate (Na2S04 . lOHgO) were dissolved in 

 50 c.c. of solution 1 (= 0-5117 grm. laevulose) and 5 c.c. of basic lead 

 1 Trans. Chem. Soc. 1897, 71, 72. 



