CHEMICAL SELECTION OF MOTHEKS. 105 



farmers when beets are purchased by the manufactur- 

 ers on the basis of a sliding scale depending 

 upon sugar percentage. By this new method the 

 beet sample must be a very fine pulp, obtained 

 as usual with' the rasp just mentioned; 26.048 

 grams are weighed in a capsule of a known 

 weight, 5 c. c. of sub-acetate of lead and 172 c. c. 

 of water are then added, giving a total of 177 c. c* 

 The capsule is covered and is then thoroughly agitated ; 

 polarization follows after having added a few drops of 

 acetic acid. 



The complete apparatus, shown in engraving (Fig. 

 40), consists of a reservoir, L, of distilled, or rain 

 water, connected by a rubber pipe with pinch cock, V, 

 to the tube, C, of the pipette (see Fig. 41). The flask, M, 

 contains subacetate of lead in communication with 

 pipette, B, by means of a rubber pipe, on which is the 

 pinch cock, V. When the pipette is too full, the over- 

 flow can run through A into flask, 5', on the lower level. 

 The flask, 0, contains acetic acid, which is used to 

 clean the pipette, which latter is held in a vertical posi- 

 tion by a suitable support. T is the capsule in which 

 the rasped pulp is weighed, and into which the con- 

 tents of the pipette are emptied. This arrangement 

 can be made to suit the special demands of any labor- 

 atory. One precaution is very important, viz., that 

 the flask, M, be not higher than six inches above B, so 

 that the flow be not too rapid, and so that the 5 c. c. 

 mark may be under mathematical observation. The 

 water reservoir should be at least three feet higher 

 than the pipette, so as to allow for its rapid filling. 



The pipette is filled in the following manner: One- 

 fourth of a turn of K opens communication with M; 



•Experiments show that beets contain 4.76 per cent, marc, or for 

 26.048 grams, 1.24 of marc and 24.81 grams of juice. It juice has an av- 

 erage density of 1.07, there will he 23.18 c. c. or 23 c. c, making allow- 

 ance for the lead deposits. If 177 c. c. water is added, this makes up 

 exactly 200 c. c. and no allowance need be ujade for froth. 



