260 POPULAR ECONOMIC BOTANY. 



stearine candles and marine soap. Southern Europe sends 

 a sweet vegetable oil, the use of which renders our woollen 

 cloths more durable and beautiful ; and the essential oils, 

 which are collected in many parts of the world, enable us to 

 communicate the odour and flavour of the most admired plants 

 to food, confectionery, medicine, and perfumery. All oils 

 naturally formed consist of two other oils, one solid, stea- 

 rine ; the other fluid, oleine or elaine. In some vegetable 

 oils the mixture of the two is owing to the temperature, any 

 decrease of which precipitates the solid from the fluid ; as, 

 for instance, when olive oil is acted upon by cold. Oleine 

 and stearine are oxides of a peculiar substance called by 

 chemists glyceryle, from its liquorice-like sweetness ; in other 

 words, oleine consists of an acid called oleic acid, and this 

 sweet substance glyceryle, whilst stearine is a compound of 

 stearic acid and glyceryle. This peculiar composition of 

 oils, both animal and vegetable, leads to their great value 

 in the formation of soaps, the process of which consists in 

 combining either soda or potash with the stearic and oleic 

 acids; this is easily effected, as the acids have a greater 

 affinity for the alkalies than for the glyceryle. The solid 

 vegetable fats are — 



