BEETROOT SUGAR IN FRANCE. 273 



The use of lime as a defecator in the way described is 

 almost a necessity, but is attended with the grave disad- 

 vantage of a certain amount of sugar being destroyed as well 

 as impurity separated. This being so, it will be obvious that 

 every trace of lime, over and above the quantity that has 

 expended its chemical virulence in effecting albuminous sepa- 

 ration, should be either separated or neutralised. In the 

 Cambrai manufactory I saw this accomplished by the very 

 elegant and, chemically speaking, unobjectionable experi- 

 ment of forcing carbonic-acid gas through the lime-charged 

 solution. The result is chalk, a perfectly harmless substance. 



The evaporative devices used in these factories are various. 

 They mostly culminate in the vacuum-pan ; but evaporation 

 in its earlier stages, up to the density best adapted to promote 

 the bleaching action of bone-black, admits of much variety. 

 To describe them comprehensively would need a treatise. 



