SUGAR-CANE SIRUP MANUFACTURE 29 
SULPHURING 
The juice is next treated with sulphur fumes (sulphur dioxide). 
As the absorption of sulphur dioxide increases the acidity of the 
juice, the best means of determining when sulphuring has gone far 
enough is to test the juice for its degree of acidity. This simple 
chemical test can be easily learned and requires but little apparatus 
and skill. Those who are unfamiliar with the chemical principles 
involved but who wish to use the method can best learn how it is 
done by consulting a chemist or by visiting a sirup or sugar factory 
where 1t is practiced. Juice is usually subjected to the action of 
sulphur dioxide until its acidity is such that 10 cubic centimeters of 
the juice will require 3.5 to 4 cubic centimeters of tenth-normal 
alkah for neutralization, using phenolphthalein as an indicator. 
This chemical test is considered an accurate means of control for 
obtaining the degree of sulphuring required for the manufacture of a 
uniform product. 
In many Louisiana sirup factories men have become so skillful 
from long experience that they can regulate the sulphuring and the 
subsequent addition of lime to insure a sirup of fully as good quality 
as that made in plants where the entire process is under chemical 
control. The control of clarification, however, may not be left to an 
unskilled man, who knows neither from experience nor by chemical 
test how to regulate the clarification. In the clarification of cane 
juice chemicals must be used in exactly the right proportion; other- 
wise the sirup produced is almost always inferior. Types of appa- 
ratus used in sulphuring are described on page 49. 
LIMING 
Milk of lime screened free from lumps and of approximately 15° 
Baumé density (26° to 27° Brix) is added to the cold sulphured 
juice, with thorough mixing, until 10 cubic centimeters of the juice, 
to which has been added a few drops of phenolphthalein, requires 
the addition of.1 to 1.5 cubic centimeters of tenth-normal alkali to 
produce a permanent slightly pink color. The quantity of milk of 
lime required to effect a good clarification varies with the character 
of the juice and degree of sulphuring, and must be determined by 
trial. As a rule it is best to add as little lime as may be required to 
give a greenish-yellow juice, from which the precipitate sediments 
readily (10 to 15 minutes) after the limed juice has been heated to 
boiling. Enough lime to make the juice alkaline must never be 
added; the juice must always remain acid, for alkaline juice yields 
a very dark sirup. Moreover, the addition of too much lime makes 
the juice decidedly yellow or reddish-yellow, even if it remains 
slightly acid. Although such juice may be clear and bright, it will 
yield too dark a sirup. Inexperienced operators often use an excess 
of lime in an effort to obtain a brilliantly clear juice, believing that 
this is required for the production of a clear sirup of good color. 
_ A milky turbidity in the sedimented juice is not objectionable; in 
fact, juice properly clarified by the sulphur-lime process nearly 
always is slightly turbid, and this appearance serves as a guide to 
the quantity of lime required for effective clarification. 
Liming is best accomplished in several clarifiers (at least three). 
While the first contains sedimenting juice the second is being emptied 
and the third is being filled. 
