414 CHEMICAL DISCOVERY AND INVENTION 



be understood that the process is essentially based on liquid 

 diffusion in which sugar and the salts present pass as " crys- 

 talloids " through the walls of the cells of the beet -tissue, 

 while the gummy and albuminous matters being "colloidal" re- 

 main for the most part behind in the pulp. Mere expression of 

 the juice would not, therefore, lead to satisfactory results, as the 

 fluid would in that way be loaded with uncrystallisable matters 

 which would be difficult to remove. 



Beet contains about 15 per cent of sugar, which even rises 

 under favourable circumstances to as much as 18 per cent. A 

 small quantity remains in the waste pulp. 



CH,-OH CKU-OH 



r 



o 



L 



CH-OH 



I 

 CH 



CH-OH 



I 

 CH-OH 







CH 



CH-OH 



I 

 CH-OH 



C 



CH O/ CH,-OH 



Common sugar belongs to a large class of chemical compounds 

 called " carbohydrates " from the fact that their composition 

 may be expressed by a formula in which there is just the pro- 

 portion of hydrogen present sufficient to form water with the 

 oxygen. Thus the composition formula of sugar is 



Ci 2 H 22 Oii 



in which the number of hydrogen atoms is double that of the 

 oxygen or 11H 2 0. 



Nearly all these substances are important constituents of food, 

 and they may be divided into two main groups, namely the 

 crystalline sweet substances known as sugars, and the non- 

 crystalline and nearly tasteless constituents of many vegetable 

 tissues such as starch, gum, and cellulose. Both these groups 

 include a great many members or distinct individuals from the 

 chemical point of view, and the interest of the subject has been 

 greatly increased within the last few years by the success which 

 has attended their investigation, more especially by Professor 



