On the Mamifactvre of Muscovado Sugar. 309 



stance which constitutes the chief difference between the 

 finest and the basest indigo. 



The herbaceous matter of cane-juice, like that of indigo, 

 varies with the constitution of the plant in different soils and 

 seasons, and especially in respect to its solubility ; insomuch 

 that some juices hold about — i— dth part of it in strict solu- 

 tion after boiling, wliile others hold not lOOOdth. 



But as herbaceous matter is rendered more soluble by the 

 intervention of carbonic acid, any cane-juice holds more 

 herbaceous matter in solution before it has been heated, than 

 it can retain at the temperature of yawing or boiling. 



For in the augmented temperature the carbonic acid for- 

 sakes the herbaceous matter to combine with that which 

 makes the acid aeriform ; the minute gaseous bubbles ia 

 their escape agitate and impel the particles lately thrown out 

 of solution, until in their coalescence they become not only 

 visible but large. We may express this change in the clear 

 recent juice by the agency of lire alone, as th« workmen do, 

 by saving the liquor breaks. 



Fresh cane-juice begins to break when the heat approaches 

 to 140 degrees of Fahrenheit; and the herbaceous matter, 

 which has felt no greater heat, has an olive green colour. 



Whether this be exposed to greater heat, or we advert to 

 that which is thrown out during the subsequent reduction 

 of the juice to sugar, the herbaceous matter is found to 

 change colour with the increase of temperature, through 

 gradations of yellow, olive, and brown, increasing in inten- 

 sity and darkness until the matter is charred to blackness. 

 As it changes in colour it becomes less soluble. The car- 

 bonic acid continues to escape, and the extricated herbaceous 

 matter accumulates to the surface, while the liquor is heated 

 to 195". 



Now the watery vapour arising with the carbonic acid 

 bubbles, pushes the cleansed liquor frothing white through 

 intervals in the swollen scum. This, which is called yauingy 

 shows that a greater heat would cause a boiling commotion: 

 but if some time be allowed for the residuary carbonic acid 

 to escape, the liquor will not boil until this heat amounts to 

 ^06'*, or within five degrees of the heat of boiling water. 



U3 The 



