560 CHANGE OF MARGARINE INTO OLEIC ACID. 



When pure, ihis oily ncid is colourless and transparent, and is re- 

 markahle for the lapidi y with which it absorbs oxygen from the atmos- 

 phere, and becoines convirted into new chemical compounds. It is re- 

 presented by the formula 34C + 31H -f 50, or C34 H31 O5. 

 Let us compare this formula with that of the marg;aric acid : 



Margaric acid = C34 H34 O4 



Butter oleic acid . . . . = C34 Hu O5 



Ditference +H3 — Oi 



or, if 3 of hydrogen be taken from the margaric acid and 1 of oxygen 

 added to it, it will be converted in(o tlie oleic acid. 



Now this may be etlected by simply sup[)()sing one atom of margaric 

 acid to absorb four atoms of oxygen from the atmosphere. Thus — 



1 of margaric acid = C34 H34 O4 



4 of oxygen . . = O4 



• 1 of oleic acid + 3 of water. 



C;m H34 Os , or C34 H31 O5 + 3HO. 



So that either in the body of the animal, in the milk while it remains 

 in the udder, or when it is exposed to the air after being drawn from the 

 cow, or even in the churn itself, it may happen that a portion of the 

 margaric acid may absorb oxygen and become changed into the oleic 

 acid. It may also be that this change, this absorption of oxygen, is pro- 

 moted by warm and retarded by cold weather, and that thus the butter 

 is rendered generally softer in the summer and harder in the winter sea- 

 son. But these are as yet only conjectures ; for, after all, the relative pro- 

 portions of the soft and hard fat in butter at different times of the year 

 may depend upon natural differences in the herbage at the several 

 seasons, or upon some other causes which have not as yet been in 

 vestigated. 



6°. Butyric, capric, and caproic acids. — These substances, as I have 

 already stated to you, exist in butter only in small quantity — to the 

 amount of 2 or 3 per cent. To these acids, and especially to the capric 

 and caproic, butter owes its disagreeable smell when it becomes rancid. 

 They do not exist, naturally, to any unpleasant extent in perfectly fresh 

 butter — they are gradually formed in it, however, when fresh butter 

 is exposed to the air. I do not enter into any detail of their proper- 

 ties, or of the mode of extracting them from butter, because these points 



fats in combination with the fatty acid. Ttiis acrolein is represented by C6 H4 O2, which 

 is exactly the constitution of 2 of lipyle. So that according to this view the solid fat of but- 

 ter would consist of— 



2 of margaric acid . . . . = CC8 1168 OS 



1 of acrolein = Cr, H4 .O2 



2 of margaric acid . , . . = C74 II72 Oio 



and, by a like substitution of acrolein for oxide of lipyle, may the constitution of butter-oil 

 be represented. 



The principal known fact in favour of this view of Redtenbacher is, that when glycerine is 

 distilled with anhydrous phosphoric acid, acrolein is produced. He supposes that the acid 

 takes the elements of 3 atoms of water from glycerine, forming acrolein : since if from — 



1 of glycerine = C6 H7 05 we take 



3 of water = Hg O3 



Acrolein remains := Cs H4 O2 



The convsrsion of acrolein into glycerine, when it is separated from the fatty acids, is sup- 

 posed to proceed, as in the case of lipyle, from its combination with the water at the moment 

 of extrication. Further r^archss are yet required to clear up this subject. 



