NOTES AND COMMENT 367 



reveals the characteristic precipitate in the cells in the local areas where 

 the sugar occurs. 



A modification of this solution which gives accurate quantitative 

 determinations is described in the second paper cited above. This 

 solution is prepared as follows: 



Copper sulphate crystals — 18.0 grams, dissolve in 100 cc. distilled 

 water. 



Sodium carbonate crystals — ^200.0 grams. 



Sodium citrate, 200.0 grams. 



Potassium sulphocyanate, 125.0 grams. 



Dissolve these three with heat in enough water to make about 800 

 cc. of solution and filter. 



Potassium ferrocyanide, a 5% solution. 



Pour the copper sulphate solution into the hot triple solution with 

 constant stirring, add 5 cc. of the 5% potassium ferrocyanide so- 

 lution, dilute to exactly 1000 cc. and the solution is ready for use and 

 will keep indefinitely without any special precautions. 



Only the copper salt need be weighed with exactness. 



Twenty-five cc. of the reagent are reduced by 0.050 gram of glucose 

 by 0.053 gram of levulose. 



"Sugar estimations are conducted with the solution in the following 

 manner: Measure 25 cc. of the reagent into a porcelain evaporation 

 dish (25-30 cm. in diameter) and add 10-20 grams of crystallized 

 sodium carbonate (or one-half the weight of the anhydrous salt) and a 

 very small quantity of powdered pumace stone. Heat the mixture 

 to vigorous boiling over a free flame and run in the sugar solution quite 

 rapidly until a heavy white precipitate is produced, and the blue color 

 of the solution begins to diminish perceptibly. From this point the 

 sugar solution is run in more and more slowly, with constant vigorous 

 boiling, until the disappearance of the last trace of blue color, which 

 marks the end point." When solutions rich in sugar are tested they 

 should be diluted 1 : 10. Toward the end of sugar solution should be 

 added a drop or two at a time with intervals of half a minute. Chloro- 

 form must not be present. 



I hope that this note may be the means of eliminating one of the many 

 sources of trouble upon which the directors of botanical laboratories 

 are compelled to keep a watchful eye.— H. M. Benedict. 



Dr. H. Brockmann-Jerosch, Dr. E. Riibel and Prof. C. Schroter, 

 all of Ziirich, form a committee which was charged with the plans and 



