90 MANUAL FOR SUGAR GROWERS. 



phenol-phthalein as a guide ; or, better, to temper as 

 for refinery muscovado, and, after clarifying, to boil 

 to a density of about 20 B., and then subside, that 

 is, allow the syrup to stand for twelve hours, in or- 

 der that any sediment may fall to the bottom of the 

 tank, the clear syrup being removed by carefully 

 drawing down, leaving the sediment undisturbed. 

 After subsiding, the syrup is made slightly acid by 

 means of sulphurous acid produced by burning sul- 

 phur and passing the fumes into the syrup. (See 

 Chapter VII.) 



Light-coloured sugar may also be made by tem- 

 pering and clarifying in the usual manner, then ren- 

 dering the juice slightly acid with phosphoric acid, 

 various forms of which are now sold for this purpose. 



In the analysis of cane-juice on page 85 there 

 appears "organic matter other than sugar." This 

 consists largely of albumen, a substance not unlike 

 white of egg in character. On adding lime in proper 

 quantity and heating this, albumen is thrown out 

 of solution, and, as the liquid becomes hot, rises to 

 the surface in the form of a scum. 



It is well to remember why a scum forms. It is 

 due to the fact that the heat drives out of the liquid 

 a certain quantity of the air which the cane-juice 

 contains in solution. The presence of dissolved air 

 in the juice is readily understood if the foaming con- 

 dition in which it leaves the mill is observed : this 

 air as it is liberated attaches itself in little globules 

 to the floating solid particles in the juice, the albu- 

 men, etc., and buoys them up to the surface, where 

 a thick scum is formed. It will at once be seen that 



