CULTURE OF THE SUGAE BEET. 85 



upper edge of the disc is provided with two sets of divisions, one to in- 

 dicate degrees of the circle, and another to indicate hundredths of sugar 

 in the solution. This provision renders it possible to use the instrument 

 for ordinary polariscopic work other than the determination of sugar, 

 while the second admits of reading percentages of sugar without the 

 otherwise necessary calculations. The plate is also provided with a 

 vernier to assist in reading parts of divisions, and to the vernier is at- 

 tached by an arm a magnifying glass to facilitate reading the indications, 

 and a mirror, so arranged as to reflect the light from the lamp used upon 

 the disc, thus obviating the necessity for an accessory light. There is 

 also a special arrangement for so turning the Nichols prisms as to ad- 

 just them before taking observations, as well as to secure the maximum 

 intensity of light when working with colored solutions, thus avoiding 

 the decoloration of many solutions before observation that would other- 

 wise be absolutely necessary. There are other ingenious mechanical ap- 

 pliances connected with the instrument which increase its usefulness, 

 but for the further description of the instrument we must refer the 

 reader to Maumene's Traitede la Fabrication du Sucre, or to the descrip- 

 tive circular of the inventor and manufacturer, whose address is No. 25, 

 rue de l'Odeon, Paris. 



The other method for estimating sugar in solutions referred to is that 

 depending upon the reduction of cupric oxide to cuprous oxide, and is 

 based upon the use of modifications of the well known Tromner's or 

 Fehling's solution. The formula more lately employed is that given by 

 Violette, and is as follows : 



Prepare a solution composed of 36.46 grams pure crystallized sulphate 

 of copper and 140 cubic centimeters of distilled water. Then a second 

 solution containing 200 grams pure crystallized Eochelle salts and 500 

 cubic centimeters of solution of caustic soda at 24° B. or 1.199 specific 

 gravity. 



When the solution of the two salts is completed (it may be hastened 

 by means of heat if necessary) the first is carefully poured into the sec- 

 ond, interrupting the operation from time to time to agitate the mixture 

 in order to dissolve the precipitate which forms. The transfer is com- 

 pleted by washing the vessel which contained the first solution with 

 distilled water. The mixture is then allowed to cool to 60° F. and the 

 volume is increased to 1 liter. 



One cubic centimeter of the solution thus prepared corresponds to 

 0.005 gram of cane sugar. Yogel proposed substitution of glycerine for 

 Eochelle salt to render the solution more stable and prevent the gradual 

 deposition of cuprous oxide, but this does not seem in all hands to have 

 proven effectual. Pellet claims to have devised a thoroughly stable 

 solution which he prepares by the following formula, substituting sodic 

 carbonate for sodic hydrate, and adding a small quantity of amnionic 

 chloride. It has the merit of being easily prepared. It is a modifica- 

 tion of those of Fehling, Violette, Possoz, and others. He uses alkaline 



