134 ORGANIC AGRICULTURAL CHEMISTRY 



Derivatives of allyl alcohol which contain sulphur are contained 

 in oil of garlic and some containing the iso-sulphocyanate group 

 are found in oil of mustard. Acrolein or acrylic aldehyde is 

 the sharp smelling substance produced when glycerol or fats are 

 heated. 



Oleic acid, a higher acid of the ethylene series containing 

 eighteen carbon atoms and one doubly linked group of two 

 carbon atoms, is found as a glycerol ester in fats and oils, 

 especially in olive oil, maize oil, cotton seed oil and a small 

 amount in butter. 



Linolic acid, an eighteen-carbon acid, containing, probably, 

 two groups of doubly linked carbon atoms, is found as a glycerol 

 ester in linseed oil. We may compare here three of the acids 

 found as glycerol esters in fats, each of which contains eighteen 

 carbon atoms, but two of them are poorer in hydrogen than the 

 other and belong to the unsaturated series. 



C18H36O2 C18H34O2 C18H32O2 



Stearic acid Oleic acid Linolic acid 



Saturated acid Unsaturated acid Unsaturated acid 



Methane series Ethylene series 



Occurs as glyc- Occurs as glycerol Occurs as glyc- 

 erol ester ester in butter erol ester in 

 in beef fat. fat. linseed oil. 



These unsaturated acids, and the fats which contain their 

 esters, like the hydrocarbons from which they are derived, 

 readily take up bromine or iodine, forming addition compounds, 

 and this reaction enables them to be distinguished and quan- 

 titatively separated from the saturated acids occurring with 

 them in fats and in oils. The property of drying oils which 

 makes them useful in paints and injurious in lubricating oils is 

 due also to the presence of these unsaturated acids, especially 

 linolic acid. 



Conclusion 



In a continuation of our study beyond the point of these un- 

 saturated compounds, and the compounds we have considered 



