ORGANIC COMPOUNDS OF PLANTS 2OI 



could be used in place of NaOH? (3) What influence did the salt 

 have upon the soap solution? (4) What was the result when 

 HC1 was added to the soap solution? (5) Why is it neces- 

 sary to weigh both the lard and the NaOH? (6) What would be 

 the result if the fat and alkali were taken in different proportions 

 from those used in this experiment? (7) Why does soap form an 

 insoluble mass with hard waters ? 



268. Fatty Acids. Formic acid, found in pine needles 

 and in red ants, has the formula H 2 CO 2 which is also 

 written HCO 2 H. Acetic acid has the formula H.CH 2 . 

 CO 2 H, and differs from formic acid simply in containing 

 CH 2 more than found in formic acid. If CH 2 were added 

 to acetic acid, H.C 2 H 4 .CO H, propionic acid would be 

 produced. This is present in some plants. In like 

 manner, butyric acid can be produced from propionic 

 acid. By the addition of CH 2 , about twenty acids can be 

 formed in the way described. This list includes palmitic, 

 stearic and other acids found in fatty bodies and named 

 fatty acids ; various of these are present in nearly all 

 foods. When a series of compounds, like the fatty acids, 

 shows a uniform difference between two adjacent members 

 the term homologous series is employed. 



269. Waxes. Wax is similar in composition to fat, 

 but contains an ethyl radical in place of the glycerol 

 radical. Beeswax, for example, is composed of palmitic 

 acid and ethyl radicals. Waxes, like fats, undergo saponi- 

 fication and are considered as having the same food 

 value. 



270. Food Value of Fat. Fat is the most concentrated 

 non-nitrogenous nutrient of foods. On account of con- 



