i68 ROOTS, GREEN FODDERS, ETC. 



to a tall cylinder, and its density measured by a Brix 

 hydrometer. It is usually found necessary to destroy 

 the froth on the surface with a few drops of ether. 



The Brix instrument is graduated to give, in direct 

 percentages, the solids in solution (the readings being 

 corrected for temperature according to a scale on the 

 bulb). 



166. Sugar in Juice, 



This is estimated in a polarimeter, which should be 

 graduated in sugar degrees, i.e., in such a manner that 

 the percentage of cane sugar can be read off without 

 calculation. According to the type of instrument, there 

 is a normal weight of sugar which should be used in a 

 200 mm. tube for the graduation. 



The volume containing the treble normal weight 

 (16-19 for a Laurent instrument) of the juice is 

 calculated or ascertained from tables. This volume, e.g. 

 (containing 48-57 grams), is measured from a burette into 

 a loocc. measuring flask. An Erdmann float should be 

 used in the burette. To the flask is added 5 c.c. of basic 

 lead acetate solution,^ the mixture well shaken, and a little 

 ether added to dispel froth. The flask is then filled up 

 to the mark with distilled water, the solution filtered, 

 and the filtrate polarised in a 200 mm. tube. 



The "sugar degrees" reading divided by 3 gives 

 the percentage of sugar in the juice. 



If desired, the dextrose present may be determined 

 indirectly by estimating the true cane sugar after 

 inversion (see 19, p. 33), or by reduction of Fehling's 



^ Basic lead acetate solution is the most satisfactory clarifying 

 agent known, and is prepared by boiling 264 grams of yellow 

 litharge with 464 grams of neutral lead acetate in 1000 c.c. of 

 water for half an hour. The liquid is then allowed to cool, diluted 

 to 2 litres, left to settle, and decanted. 



