THE ORIGIN OF SOAP. 288 



wliere wood fires prevail. It is the old-fashioned practice 

 of pouring water on the wood ashes, and using the "lees" 

 thus obtained. These lees are a solution of alkaline car- 

 bonate of potash the modern name of potash being derived 

 from the fact that it was original!}* obtained from the ashes 

 under the pot. In like manner soda was obtained from the 

 ashes of seaweeds and of the plants that grow near the sea- 

 shore, such as the salsover soda, etc. 



The pot-ashes or pearl-ashes being so universal as a. do- 

 mestic bi-product, it was but natural that they should be 

 commonly used, especially for the washing of greasy clothes, 

 as they are to the present day. Upon these facts we may 

 build up a theory. of the origin of soap. 



It is a compound of oil or fat with soda or potash, and 

 would be formed accidentally if the fat on the surface of the 

 pot should boil over and fall into the ashes under tSe pot. 

 The solution of such a mixture if boiled down would give 

 us soft soap. 



If oil or fat became mixed with the ashes of soda plants, 

 it would produce hard soap. Suqj^ a mixture would most 

 easily be formed accidentally in regions where the olive 

 flourishes near the coast, as in Italy and Spain for example, 

 and this mixture would be Castile soap, which is still largely 

 made by combining refuse or inferior olive oil with the soda 

 obtained from the ashes of seaweed. 



The primitive soap-maker would, however, encounter one 

 difficulty that arising from the fact that the potash or soda 

 obtained by simple burning of the wood or seaweed is more 

 or less combined with carbonic acid, instead of being all in 

 the caustic state which is required for effective soap-making. 

 The modern soap-maker removes this carbonic acid by 

 means of caustic lime, which takes it away from the car- 

 bonate of soda or carbonate of potash by simple exchange 

 i.e., caustic lime plus carbonate of soda becoming caustic 

 soda plus carbonate of lime, or carbonate of potash plus 

 caustic lime becoming caustic potash plus carbonate of lime. 



How the possibility of making this exchange became 

 known to the primitive soap-maker, or whether he knew it 

 at all, remains a mystery, but certain it is that it was prac- 

 tically used long before the chemistry of the action was at 



