CANE SUGAR. 



2. Influence of Acid. The constant k was determined by Ostwald 13 in 

 1884, for a large number of acids; some values as found by him are given 

 below. These are referred to half normal strength, to 25 C. temperature, the 

 time being expressed in minutes, and the logarithms being common ones. 



Acid. Constant. | Acid. Constant. 



Hydrobromic -002187 Sulphurous . ..... '0006630 



Hydrochloric -002438 Oxalic -0004000 



Nitric -002187 Phosphoric -0001357 



Sulphuric -001172 Acetic -0000088 



3. Effect of Concentration of Acid. Within comparatively narrow limits 

 the rate of inversion is nearly directly proportional to the concentration of the 

 acid. With the stronger acids, however, the rate of inversion decreases more 

 rapidly than does the decrease in concentration ; with weaker acids, the reverse 

 holds. 



4. Effect of Temperature. The following empirical equation, due to 

 Urech, 14 connects velocity of inversion and temperature: 



A CTt T ) 



C 1 = C i) -e T O I* 



where C and C l are the rates of inversion at T and T lt e is the base of 

 the natural system of logarithms, and A is a constant, and equal to 12820. 

 Putting the rate of inversion at 25 C. = l, this expression gives the 

 following rates of inversion at the stated temperatures : 



The Effect of Neutral Salts. It was originally shown by Arrhenius 15 

 that the rate of inversion by acids was accelerated by the presence of the 

 halides and nitrates of the alkalies and alkaline earths. The writer 16 has 

 extended his observations, and has found : 



1. In concentration up to '02 N at 100 C., the halides and nitrates 

 have an inappreciable effect on the rate of inversion with very dilute acids. 



2. Under similar conditions the sulphates, sulphites, oxalates, and all 

 ^alkali and alkaline earth salts of weaker acids retard inversion. 



3. In concentration of acid and salt of the normal order, at ordinary 

 temperatures, the halides and nitrates of the alkalies and alkaline earths 

 .accelerate the rate of inversion ; the acceleration increases progressively from 

 chloride to bromide, to iodide, the effect of nitrates being similar to that of 

 chlorides. A difference in the base of the salt has very little, if any, effect ; 

 thus, the acceleration due to sodium chloride is substantially the same as that 

 -due to calcium chloride. 



256 



