A REACTION VELOCITY EXPERIMENT JACK.
P. MONTGOMERY, UNIVERSITYOF ALABAMA.UNIVERSITY,ALABAMA
The inversion of cane sugar has long been a favorite reaction for the measurements of constants of reaction velocity. When cane sugar is dissolved in water, containing a small amount of free acid, i t is slowly hydrolyzed into glucose and fructose. The progress of the reaction is usually followed by means of the polarimeter. Since the specific gravity of the solution changes during the inversion, the progress of the reaction can be readily followed by the use of an ordinary Westphal balance. This procedure may be of value in a laboratory where a polarimeter is not readily available or when a variation of method is desirable. One hundred grams cane sugar were dissolved in 150 cc. water a t 20°C. Five cc. sulfuric acid were added and, after mixing, the temperature of the solution was quickly adjusted to 25", which was the temperature throughout the experiment. By means of the Westphal balance the specific gravity of the solution was observed a t intervals, as shown by the following table: Minulcs
0 60 80 170 200 250 300 Final
SP. Gr.
1.1970 1.2000 1.2025 1.2070 1.2075 1.2090 1.2100 1.2140
Chnngr
k
0.0045 0.0055 0.0100 0.0105 0.0120 0.0130 0.0170
0.00222 0.00213 0.00225 0.00207 0.00212 0.00208
Applying the well-known formula,
k = t1 - 1 oa g - rL for unimolecular reactions i t is obvious that a is 0.017 and that x in each step is to be found in the third column, "Change," inits respective line. The values of k in the fourth column were worked out by application of the formula to the data from the table.
