134 METHODS OF ANALYSIS [Chap. 



40 Invert Polarization. — Tentative. 



(a) At SO°C. — Invert 50 cc. of the solution obtained in 39 as directed under 

 VIII, 14 or 16, and polarize at 20°C. in a 200 mm. tube. 



(b) At 87°C.— Polarize the solution, obtained as directed in (a), at 87°C. in a 200 

 mm. jacketed tube. 



41 REDUCING SUGARS.-TENTATIVE. 



Dilute 10 cc. of the solution, used for direct polarization, 39, to 250 cc. and de- 

 termine reducing sugars in 25 cc. of this solution by one of the methods given under 

 VIII, 25, 36, 39 or 56, respectively. Calculate the result to per cent of invert 

 sugar. 



42 SUCROSE.— TENTATIVE. 



Proceed as directed under VIII, 18. Determine reducing sugars after inver- 

 sion by diluting 10 cc. of the solution obtained in 40, with a small amount of water, 

 neutralizing with sodium carbonate, and making up to 250 cc. with water. Employ 

 50 cc. of this solution for the determination, using the same method as in 41 . 



43 LEVULOSE.-TENTATIVE. 



Multiply the direct reading at 87°C., 39 (d), by 1.0315 and subtract the product 

 from the constant direct polarization at 20°C., 39 (b): divide the difference by 2.3919 

 to obtain the grams of levulose in a normal weight of the honey. From this figure 

 calculate the per cent of levulose in the original sample. 



44 DEXTROSE.— TENTATIVE. 



Subtract the per cent of levulose, obtained in 43, from the per cent of invert 

 sugar, found in 41 , to obtain the approximate per cent of dextrose. 



The dextrose can be determined more accurately by multiplying the per cent 

 of levulose, as found in 43, by the factor 0.915, which gives its dextrose equivalent 

 in copper reducing power. Subtract this figure from that of the reducing sugars, 41 , 

 calculated as dextrose, to obtain the percentage of dextrose in the sample. (Owing 

 to the difference in the reducing powers of different sugars, the sum of the dex- 

 trose thus found and the levulose as obtained in 43 will be greater than the amount 

 of invert sugar obtained in 41). 



45 DEXTRIN (APPROXIMATE).-TENTATIVE. 



Transfer 8 grams of the sample (4 grams in the case of dark colored honey-dew 

 honey) to a 100 cc. flask (using not more than 4 cc. of water) by allowing the sam- 

 ple to drain from the weighing dish into the flask and then dissolving the residue in 

 2 cc. of water. After adding this solution to the contents of the flask, rinse the 

 weighing dish with two 1 cc. portions of water to which a little alcohol is added sub- 

 sequently. Fill the flask to the mark with absolute alcohol, shaking constantly. 

 Set the flask aside until the dextrin has collected on the sides and bottom and the 

 liquid is clear. Decant the clear liquid through a filter paper and wash the resi- 

 due in the flask with 10 cc. of 95% alcohol, pouring the washings through the same 

 filter. Dissolve the dextrin in the fiask with boiling water and filter through the 

 filter paper already used, receiving the filtrate in a tared dish, prepared as directed 

 under 4. Rinse the flask and wash the filter a number of times with small portions 

 of hot water, evaporate on a water bath and dry to constant weight in vacuo 

 at 70°C. 



