THE CARBOffi'DRATES AXD FATS 17 



fatty acids with glycerin, and may be termed glycerides or glyceric 

 ethers. The term hydrocarbon, applied to them by some authors, is 

 wholly incorrect. 



The fatt)- acids form a series of acids derived from the monatomic 

 alcohols by oxidation. Thus, to take ordinary ethyl alcohol, C9H5HO, 

 the first stage in oxidation is the removal of two atoms of hydrogen 

 to form aldehyde, CH3.COH : on further oxidation an atom of oxygen 

 is added to form acetic acid, GH3.COOH. 



A similar acid can be obtained from all the other alcohols 

 thus: — 

 Prom methyl alcohol CH3.HO, formic acid H.COOH is obtained 



Or in general terms : — 



Prom the alcohol with formula C^Hon+i-HO the acid with formula 

 C,_iH2,_i.C0.0H is obtained. The sixteenth term of this series has 

 the formula C,5H3,.CO.OH, and is called palmitic acid ; the 

 eighteenth has the formula C17H35.CO.OH, and is called stearic acid. 

 Each acid, as will be seen, consists of a radicle, C„_,H2„_,C0, united 

 to hydroxyl (HO). 



Oleic acid, however, is not a member of the fatty acid series 

 proper, but belongs to a somewhat similar series of acids known as 

 the acryhc series, of which the general formula is C,_,H2„_3COOH. 

 It is the eighteenth term of the series, and its formula is C, 7H33.CO.OH. 



Glycerin or Glycerol is a triatomic alcohol, C3H5(OH)3 — i.e. three 

 :oms of hydroxyl united to a radicle glyceryl (C3H5). The hydrogen 

 in the hydroxyl atoms is replaceable by other organic radicles. As 

 an example take the radicle of acetic acid called acetyl (CH3.CO). 

 The following formulae represent the derivatives that can be obtained 

 by replacing one, two, or all three hydroxyl hydrogen atoms in this 

 way :— 



(OH (OH (OH (O.CH3.CO 



CaHj-'oH C3H5-OH C3H5- O.CH3.CO C3H5-O.CH3.CO 



ioH iO.CH3.CO (O.CH3.CO 'O.CH3.CO 



[glycoin] [monoacetin] [diacetin] [triacetin.] 



Triacetin is a type of a neutral fat ; stearin, palmitin, and olein 

 jught more properly to be called tristearin, ti-ipalmitin, and triolein 



