Q2 Green . — On Vegetable Ferments. 
tracted it with alcohol of 10-20 per cent strength and filtered, 
when the filtrate was found to contain all the enzyme in a very 
pure condition, It can also be prepared as a dry powder by 
dehydrating the first precipitate and drying it in vacuo. 
The action of invertase on cane-sugar may be expressed by 
the equation : — 
Ci 2 h 22 o x1 th 2 o = c 6 h 12 o 6 + c 6 h 12 o 6 
Sucrose Dextrose Laevulose. 
It is a very unstable body and is easily damaged or 
destroyed, the caustic alkalis even in very small proportions 
being especially destructive. It resembles inulase in that a 
very minute trace of mineral acid favours its activity, but a 
very slight additional quantity is detrimental. The most 
favourable amount of acidity, sulphuric acid being used 1 , 
varies with the amount of invertase present, and with the 
temperature of digestion. The more of the enzyme that is in 
the solution, the greater is the amount of acid required for 
the maximum effect. Thus with -4 per cent, of invertase 
present, the optimum amount of sulphuric acid is 12*5 parts 
per million of the solution; with 1-5 per cent, the amount 
rises to 15 per million, the temperature being 56° C. If the 
experiment he conducted at 15*5° C., when 1*5 per cent, of 
invertase is used, the acid required is 75 parts per million, 
while if 15 per cent, of the ferment is present, the acid must 
be 250 parts per million. 
The influence of temperature under these conditions also 
appears from a comparison of these figures. Taking the 
invertase present as 1*5 per cent., the amount of acid required 
for the best results at 56 0 C. is 15 per million of solution, but at 
I 5 ‘ 5 ° C. it is 75 or 5 times as much. Excess of acid, even of 
very little, is prejudicial. Thus at 6o° C. an excess of only 
2 parts of acid per million lowers the rapidity of the action 
elevenfold. 
Alcohol exerts on the whole a deleterious influence, 
varying in proportion to the amount present. With 5 P er 
1 O’Sullivan and Tompson, op. cit. 
