262 CHAPTER XIII 



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

 Urech^*, connects velocity of inversion and temperature : — 



A (T^ — Tq ) 



Ci = Co e T,T, 

 where Cq and C^ are the rates of inversion at Z",, and T^, e is the base of 

 the natural system of logaiithms, and A is sl constant, and equal to 12820. 

 Putting the rate of inversion at 25° C.=i, this expression gives the following 

 rates of inversion at the stated temperatures : — 



°C. Rate. °C. Rate. °C. Rate. 



25 I I 60 9i'8 



40 7'6 ! 65 162 



45 14*3 I 70 282 



50 26-7 75 483 



55 57-7 I 80 814 



85 1354 



90 2110 



95 3573 



100 5659 



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

 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^® has 

 extended his observations, and has found : — 



1. In concentration up to 0-02 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 the sodium chloride is substantially 

 the same as that due to calcium chloride. 



4. Under similar conditions, sulphates, sulphites, oxalates, etc., retard 

 the rate of inversion. 



Effect of Invert Sugar. — The action of invert sugar on the inversion of 

 cane sugar is a peculiar subject, some investigators finding that invert sugar 

 of itself caused inversion, and others obser\dng no effect. Geerligs^', in 

 investigating the subject, came to the conclusion that invert sugar of itself 

 had no invertive action, but that in the presence of neutral salts, such as 

 chlorides, nitrates and sulphates of the alkahes and alkaline earths, inversion 

 occurred at the temperature of boiling water, owing to a slight hydrolysis 

 of the neutral salt under the influence of the invert sugar. The writer^ ^ 

 in investigating the same subject, failed to obtain any trace of inversion due 

 to the combined influence of invert sugar and neutral salts, when the latter 

 were present in normal concentration. 



Inversion under Acid Salts. — Salts of the heavy metals, such as zinc 

 sulphate, also cause the inversion of cane sugar. This has been chiefly 

 studied by Long^^ ; the inversion is ascribed to the partial hydrolysis of the 

 salt, thereby affording free hydrogen ions in solution. 



Inversion under the Influence of Enzymes. — Besides chemical inversion 

 under the influence of acids and acid salts, cane sugar is inverted by the 

 action of certain ferments known collectively as enzymes. The enzyme 

 most studied is that secreted by yeast, and known as invertase. The proper- 

 ties of this body were first investigated by O'Sullivan and Thompson^^, who 



