8 



gives a percentage which is more than 1 per cent higher than the direct reading, raffinose is 

 probably present, and the following formulae by Creydt should be used: 



P=the direct reading. 



I=the invert reading. 



S^the percentage of sucrose. 



R=the percentage of anhydrous raffinose. 



S== O5188P-I r, P^S 

 0.8454 ~~1.85' 



Determination of sucrose in the absence of raffinose. The inversion and observation should 

 be made as described above and the following formula used: 

 When the polarizations are made at 20 C. : 



X (P-I). 



142.66-- 



Should the temperature (t) vary from 20, which is permissible within narrow limits, in the 

 absence of raffinose, use the following formula: 



100 (P-I) 

 & p 



142.66-2 



ALTERNATE OFFICIAL METHOD FOR INVERSION WITHOUT THE APPLICATION OF HEAT. 



Take 50 cc of the clarified solution freed from lead, add 5 cc of hydrochloric acid containing 

 38.8 per cent of acid, set aside during a period of twenty-four hours at a temperature not 

 below 20 C. ; or if the temperature be above 25 C. set aside for ten hours. Make up to 100 

 cc at 20 C. and polarize. 



Page 43, add the following provisional methods for direct analysis 

 of sugar beets : 



(a) Scheibler's alcoholic method. In the direct analysis of the beet with the Soxhlet- 

 Sickel apparatus by Scheibler's method, proceed as follows for the extraction of the sucrose: 



Place a plug of absorbent cotton in the bottom of the tube, then introduce 26.048 grams 

 of the pulped beet, or 2x16.29 grams, according to the polariscope in use, pressing the pulp 

 lightly with a rod. Very small fragments of the beet may be used instead of pulp. Connect 

 the extractor with the reflux condenser. Place 75 cc of 95 per cent alcohol in the flask and 

 connect with the extractor; heat the flask in the water bath and continue the extraction 

 from half an hour to two hours or more, according to the state of division of the sample. 

 Use somewhat weaker alcohol if only 16.29 grams of pulp be taken. Cool and remove the 

 flask, substitute a second containing 75 cc of 75 to 80 per cent alcohol, and continue the 

 extraction to ascertain whether the first extraction were complete. 



Fill the first flask to the 100-cc mark, after treating the sample with two or three drops of 

 subacetate of lead solution. Mix the contents of the flask, filter, and polarize. Having 

 extracted the normal weight of pulp, the polariscopic reading is the per cent of sucrose in 

 the sample. 



The extract in the second flask should also be polarized as a check upon the extraction. 



Great care is essential in the polarization of alcoholic solutions. The least quantity of 

 subacetate of lead that will clarify the solution should be us^d. The solution must be pro- 

 tected from evaporation during the filtration by a cover glass. Avoid irregularities in the 

 temperature of the solution in the observation tube, due to the warmth of the hands; since 

 the density of the solution in different parts of the tube will vary under such conditions, 

 striae will form, rendering an accurate reading impossible. 



