Definitions and Terminology

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  • Definitions and Terminology

  • Fixed Oils and Essential Oils - There are distinct differences between fixed and volatile plant oils.
  • The plant oils used as carriers in aromatherapy and massage  are referred to as 'fixed' oils because they do not evaporate.
  • Plant essential oils do evaporate because they are volatile.
  • Fixed oils leave a permanent oil mark on paper because of their lubricating quality and non-volatile nature.

  • Essential oils do not leave an oily mark on paper, although any colour present will leave a stain.
    Fixed oils are not soluble in alcohol
    Essential oils generally are soluble in alcohol.
  • In general, fixed oils are miscible with ether, chloroform and petroleum spirit.
  • Essential oils dissolve easily and completely in fixed oils in all proportions; unscrupulous suppliers sometimes make use of this fact by using fixed oils to dilute essential oils in order to deceive unwary buyers.
  • Lipids - Chemically speaking, fixed oils are classed as lipids. This is a diverse family of compounds found naturally in plants and animals, and the term encompasses not only oils but also fats.
  • Although their structures are similar, at normal room temperatures (15C) fats are solid and oils are liquid.
  • Triacylglycerols - Fats and oils are formed when a special type of alcohol called glycerol reacts with a particular type of organic compound known as a fatty acid.
  • Fatty acids all have a long hydrocarbon chain (typically)containing 16 or 18 carbon atoms) attached to the carboxyl group (-CooH).
  • Some of them contain double bonds  and are said to be unsaturated, whereas those without double bonds are referred to as saturated.
  • The resulting compounds are triacylglycerols, also known as triglycerides, and a variety of these are possible. in the above chemical formula  R',R" and R2"' represent chains of carbon atoms.
  • Simple triacylglycerols are those in which R', R" and R2 are the same, ie three molecules of the same fatty acid have reacted with one molecule of glycerol).
  • Complex triacylglycerols are those in which R', R" and R" are different. Perhaps not surprisingly, naturally occurring triacyl-glycerols are all complex. 

 

  • Triacylglycerols feature in our diet, and we digest them by utilising  a lipase enzyme to reverse the above reaction.
  • This process is called saponification, and is the way in which fatty acids are made available for us in our bodies.
  • Mineral Oils - Mineral oils are hydrocarbons of high molecular weight and therefore a different class of compound from the triacylglycerols and lipids of vegetable origin.
  • Mineral oils are not broken down by the body's digestive system and because of this have no nutritional value.
  • Mineral oils  - mineral oils are also oily and greasy, but they are not used in massage  they have a tendency to clog the pores.
  • However, because of these pore sealing qualities they, are used on Babie's bottoms, to help prevent the intrusion of urine, thus reducing the risk of nappy rash.
  • Reference: Carrier Oils for Aromatherapy and Massage: Len Price with Shirley Price
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