150 THE ACTION OF HEAT. 
the solution acquired darkness of color, and at the end of 
36 hours it had become black. The effects of long appli- 
cation of the heat were: 1. The disappearance of cane 
sugar. 2. The appearance of grape sugar or glucose. 3. 
The production of carbonaceous powder and acids.” 
It is impossible, indeed, to prevent the formation of a 
small portion of darker colored liquid sugar (molasses) in 
a solution of white sugar, chemically pure, which has been 
heated to boiling, and afterward recrystallized. 
Claiming for the tilt pan no other merits than those which 
have recommended it in plantation use for the last hundred 
years, I here give place to some remarks by Prof. McCul- 
loh, founded upon the experienee of M. Payen, the emi- 
nent French chemist, in regard to open-air boiling and the 
employment of an evaporating vessel somewhat similar. 
“Tt seems to be a disputed point whether or not saccha- 
rine solutions and juices are injured in evaporation by 
exposure to the air. M. Payen, whose opinion and ex- 
perience are entitled to great credit, remarks that it is the 
more important to refute the belief that syrups are injured 
and rendered dark colored in evaporation by an elevated 
temperature, or by the action of the air aided by heat, be- 
cause these views have been sustained by eminent scientific 
men, and given rise to most ruinous speculations. In 
corroboration of his opinion that injury is done rather by 
long duration of heat, M. Payen adduces the facts that 
boiling for thirty or forty-five minutes, according to the old 
system, deepens the color, and renders a much larger quantity 
of sugar uncrystallizable than rapid concentration in six 
or eight minutes by means of a ézli or bascule pan; that 
slow evaporation, by steam, of large quantities of beet 
juice at a temperature below that of boiling water, far 
from producing a better result, gives very dark and per- 
