METHODS OF SAMPLING. 



13 



are to ho comparable. Much work has been done to determine the 

 point of sampling and it has been shown that the rasp should enter 

 near the edge of the leaf scar and take a direction at an angle of 

 45 to the main axis through the beet. This can be accomplished 

 by having the beet placed on a moving board tilted at the proper 

 angle and pressed against the rasp, or the rasp may 

 be pressed against the beet. Rasps are manufac- 

 tured which remove this core whole, or collect the 

 cuttings in the shaft of the drill (fig. 4) . The sample 

 obtained this way seldom amounts to 26 grams and 

 it is difficult to press this quantity and obtain suf- 

 ficient juice to determine the dry substance and also 

 the sugar. The per cent of sugar is determined 

 direct by one of the instantaneous methods or by 

 the hot-water digestion method. 1 Ten grams of the 

 beet pulp may be digested, made up to 38.7 cc; and 

 polarized in a 200 mm tube; the reading will be the 

 per cent of sugar. Or 6.48 grams of the cuttings 

 may be digested, made up to 50 cc, and a reading 

 made in a 400 mm tube. Again, the beet cuttings 

 in the rasp can be placed in a tared dish and the 

 w^hole weighed. The pulp is then washed into a 100 

 cc flask if the sample amounts to about 13 grams, or 

 into a 200 cc flask if it is nearly 26 grams, and a 

 water digestion is made in the usual way. The per 

 cent of sugar obtained, multiplied by the relation of 

 the weight of sample used to 26 grams gives the per- 

 centage of sugar present. A correction should be 

 made for the space occupied by the marc, 26 grams of pulp occupy- 

 ing 0.6 cc. 



The basic lead acetate solution is practically the only one used 

 for clarifying beet solutions for polarization. The clarifying power 

 of this solution depends somewhat upon its basicity. Browne 2 has 

 shown that as the basicity increases the polarization of a raw cane 



FIG. 3. Correct posi- 

 tion of boring rasp 

 in beet. 



FIG. 4. Boring rasp. 



sugar or cane sirup increases. As large an increase will hardly 

 take place in the polarization of a beet, but it shows that care must 

 be taken in the preparation of the basic lead acetate solution, 

 " Three well-defined subacetates have been prepared by the digestion 



See ]>:\l'f< IS Mini HI. 



U. S. Pept. Ajjr., Hun-sui of Chemistry Hul. ]_>_'. p. __>:!. 



