208 THE INCOME OF ENERGY 



Experiment. 1. Shake 1 c.c. neutral olive oil 

 in a test-tube with 5 c.c. 0.25 per cent sodium 

 carbonate solution. 



The oil will be broken up into large globules 

 which will speedily reunite, leaving the liquid 

 clear. 



2. Shake 1 c.c. rancid olive oil (containing 

 about 5.5 per cent fatty acid) with 5 c.c. 0.25 per 

 cent sodium carbonate solution. 



The mixture becomes instantly milky. The 

 oil is divided into globules of microscopic size. 

 The emulsion is permanent. 



3. Shake 1 c.c. neutral olive oil with 5 c.c. water. 

 The water and oil will not mix. 



4. Shake 1 c.c. neutral oil with water con- 

 taining soap. 



The oil will be emulsified. It is probable 

 therefore that soap contributes to the emulsion, 

 perhaps by coating the fine particles of oil with a 

 membrane that prevents their reunion. 1 



Gad's Experiment. 1 . Fill a watch glass 

 about 5 cm. in diameter with 0.25 per cent solu- 

 tion of sodium carbonate. With a glass rod 

 carefully place a large drop of rancid olive oil 

 (containing 5.5 per cent fatty acid) upon the 

 surface of the soda solution. 



1 Briieke : Sitzungsberichte der kaiserlichen Akademie der 

 Wissenschaften zu Wien, 1870, Ixi, pp. 613-614. 



