SUGAR-CANE SIRUP MANUFACTURE 88 
acidity without the use of any lime. For best results, the juice should 
never be limed below an acidity corresponding to 0.8 cubic centimeter 
of tenth-normal sodium hydroxide solution per 10 cubic centimeters 
of juice, using phenolphthalein as the indicator (p. 29). The lime, 
preferably milk of lime (p. 30), is always added to the cold juice before 
heating. As lime is a chemical clarifying agent, its use in proper 
proportions must be under careful control. This is fully as important 
when lime alone is used as in the process employing both lime and 
sulphur dioxide. 
EVAPORATION OF JUICE TO SIRUP 
Heating sirup clarified by lime to a high temperature at some time 
during manufacture improves its quality. When vacuum evapora- 
tion alone is practiced, the sirup usually tends to have a darker color 
and a somewhat flat flavor. Good results have been obtained 
when sirup from the double or triple-effect evaporators at about 20° 
Baumé (35.8° Brix) has been heated rapidly in the open to the boiling 
temperature, brushed or skimmed, and allowed to settle, after which 
it has been evaporated to final density in a vacuum pan and dis- 
charged to the sirup storage tanks at a temperature of 140° F. or 
lower. Another method consists in settling the sirup discharged 
from the effects at about 20° Baumé and 140° F., finishing in a 
vacuum pan to a density a degree or two lower than that required, 
boiling for a few minutes in brush pans, and discharging through a 
cooling system (p.54) into the sirup storage tanks. 
‘The equipment used for clarifying sirup by the sulphur dioxide 
and lime method (p. 42) may be used for clarifying it by hme. When 
more open evaporators are provided and when these open evaporators 
resemble the small units designed for rapid open evaporation in a 
shallow layer, however, sirup of a better quality may be expected. 
Open evaporation is more expensive than vacuum evaporation, a 
fact to be considered in connection with the market values of sirup 
produced by the two methods. 
Figure 7 shows a satisfactory continuous open evaporator with 
steam coils. The skimmings collect readily in the front end (cold 
juice space), from which they are frequently removed. Cold juice 
flows continuously into this end of the evaporator and semisirup at 
20° to 25° Baumé (35.8° to 45° Brix) is drawn off from the opposite 
end to an open finishing evaporator of the noncontinuous type. The 
steam supply and rapidity of boiling may be so regulated by adjusting 
the steam inlet and outlet valves that the foam will “float the skim- 
mings along,” partly over the edges of the evaporator into the 
skimming troughs, but mostly backward toward the cold surface. 
Hvaporation is rapid and in ashallow layer. Such an evaporator may 
be used in making sirup of the Georgia type without lime and also 
for evaporating lime-clarified juice. The principle governing the 
design of this evaporator has been Sacibved also in manufacturing 
steam evaporators of somewhat simpler construction. 
Steam coils with swing-joint connections (fig. 8) may be swung up 
out of the evaporator whenever it is necessary to scrape them. This 
design is particularly good for galvanized-iron evaporators, because 
the frequent use of hydrochloric (muriatic) acid and caustic soda, 
the most common cleansing agents for coils in copper evaporators, 
56750° —25t——3 
