16 THE CHEMISTRY OF CATTLE FEEDING 



substance of indefinite composition called caramel. At higher 

 temperatures they are completely charred the whole of the 

 hydrogen and oxygen is given off and only black amorphous 

 carbon remains. Sugar solutions form one of the most readily 

 available sources of carbon for the nourishment of moulds 

 and micro-organisms of various kinds. Under suitable con- 

 ditions they undergo many different fermentative changes. 



Sugars may be conveniently divided into two principal 

 sub-groups as follows : 



(1) Those of the general formula, C H H 2 ,,O n , not hydrolysed 

 by dilute acids. 



(2) Those which are split up by dilute acid hydrolysis into 

 compounds which belong to the first sub-group. They are 

 apparently derived from the latter by condensation or combi - 

 nation of two or more molecules with elimination of one or 

 more molecules of water. 



Sub-group i includes 



Triose (Glycerose), C 3 H 6 O 3 . 



Tetrose (Erythrose), C 4 H 8 O 4 . 



Pentoses (Arabinose, Ribose, and Xylose), C 5 H 10 O 5 . 



Hexoses (Glucoses, Mannoses, Guloses, Fructoses, Galac- 

 toses, Sorbose, Formose and /?-Acrose), C 6 H 12 O 6 . 



Heptoses, C 7 H 14 O 7 . 



Octoses, C 8 H 16 O 8 . 



Nonoses, C 9 H 18 O 9 . 



Also certain substituted products in which atoms of 

 hydrogen are replaced by alcohol radicles, e.g. phenylerythrose, 

 CeH5.C4H 7 O4. 



The substances commonly known as dextrose and laevulose 

 respectively are both hexose sugars. The former is a glucose 

 and the latter a fructose. 



Sub-group 2 includes 



Di-pentoses, C 10 H 18 O 9 . 



Di-hexoses (Sucrose, Lactose, Maltose, Melitose, etc.), 



^12^22^11- 



Tri-hexoses (Raffinose, etc.), Ci 8 H 32 O 16 . 



Hex-hexoses (Gentianose, etc.), C 36 H 62 O 31 . 



Technically, the most important sugars are those which 



