16 



ANALYSES OF SUGAR BEETS, 1905 TO 1910. 



26 grams of sugar, dissolved and made up to 100 true cubic centimeters 

 with water at 20 C., and the polarization made in a 200 mm tube at 

 the same temperature. The old normal weight of 26.048 grams of 

 sugar was for lOOMohr cubic centimeters, and probably the polariza- 

 tion was to be made at 17.5 C. 



(2) Use of the wrong flask, namely, Mohr cubic centimeter flasks 

 in place of true cubic centimeter flasks or vice versa. 



(3) Use of old polariscopes whose accuracy has not been checked. 

 A polariscope scale can be checked against pure sugar, but ordinarily 

 it is much better to check against a standardized quartz plate. 



(4) Use of sucrose pipette in place of a normal weight. This 

 pipette can be easily standardized and the error due to this source 

 checked, but in general it is better to obtain the normal or double 

 normal amount of juice by weighing. 



An error that may amount to several per cent can be introduced by 

 using the same jute cloth for pressing beets when the per cents of 

 sugar in the two samples vary greatly. A large error may also enter 

 from dilution by not removing all of the water used in washing out 

 the press after each sample. Errors in reading the Brix hydrometer 

 are sometimes due to air in the juice and also to the adherence of the 

 hydrometer to the sides of the cylinder. If these chances of error are 

 guarded against, the reading of the per cent of sugar in the juice should 

 be accurate. The following table 1 shows the possible error from the 

 use of a wrong factor: 



Variations in results obtained by using different factors . 



Should the juice polarize 20 and a factor of 90 be used when 95 is 

 the correct one, the resulting figure for the sugar in the beet is just 1 

 per cent too low. If the results by this method are used as a basis 

 for the price paid for beets, the grower would lose the price of an extra 

 per cent of sugar per ton, which varies from 20 to 25, or 33 cents. 



1 Taken from report of E. E. Ewell, Fifty-sixth Congress, first session, Doc. No. 699, p. 147. 



