FUNCTION OF WAXES 43 



WAXES. 



The chief function of waxes in plants is to form a protec- 

 tive covering against undue evaporation of water. They are 

 found most commonly in or on the cuticle of leaves and fruits 

 where they give rise to the glaucous effect. 



As already stated, the waxes resemble the fats in their 

 chemical constitution in so far as they are esters, but they 

 differ in the nature of their alcohol constituent which is not 

 glycerol but is usually a monohydric alcohol such as cetyl 

 alcohol C 16 H 33 OH, carnaubyl alcohol C 24 H 49 OH, pisangceryl 

 alcohol C 24 H 49 OH, ceryl alcohol C 2)5 H 53 OH, myricyl alcohol 

 C 30 H 61 OH, cholesterol or phytosterol C^H^OH. 



In addition to the acids already mentioned as occurring in 

 fats, the following are also met with in waxes in the form of 

 esters : ficocerylic acid C 13 H 2ti O 2 , carnaubic acid C 24 H 48 O 2 , and 

 pisangcerylic acid C 24 H 48 O 2 , as well as acids belonging to 

 series olf the general formula C n H 2n _ 2 O 2 and C n H 2n O 3 . 



The term wax used in the chemical sense has reference 

 only to the chemical composition of these substances, regardless 

 of their physical state of aggregation, and consequently both 

 liquid and solid waxes are known. 



Waxes of the former class are, however, only known in 

 the animal kingdom, they are ordinary sperm oil and arctic 

 sperm oil. 



Among the better-known vegetable waxes may be men- 

 tioned : 



(a) Carnauba Wax obtained from Copernicia cerifera ; this 

 wax contains ceryl and myricyl alcohols, and two acids, 

 cerotic acid C 26 H 52 O 2 , and carnaubic acid C 24 H 48 O 2 , together 

 with a hydroxy-acid of the formula C 21 H 42 O 3 . 



(&} Pisang Wax obtained from the leaves of Cera musae is 

 the pisangceryl ester of pisangcerylic acid. 



The following are some of the more important waxes of 

 animal origin : 



Wool wax, better known as wool fat or lanolin (which is 

 rich in cholesterol), beeswax, spermaceti, and Chinese insect 

 wax. 



