SOAP 



143 



apt to have an excess of the base ; but the better soaps are 

 carefully prepared and are either neutral or only slightly 

 alkaline. 



Soap. If we gather together scrapings of lard, butter, bits 

 of tallow from burned-out candles, scraps of waste fat, or any 

 other sort of grease, and pour a strong solution of lye over the 

 mass, a soft soapy substance is formed. In colonial times, 

 every family made its own supply of soap, utilizing, for that 

 purpose, household scraps often regarded 

 by the housekeeper of to-day as worthless. 

 Grease and fat were boiled with water and 

 hardwood ashes, which are rich in lye, and 

 from the mixture came the soft soap used 

 by our ancestors. In practice, the wood 

 ashes were boiled in water, which was then 

 strained off, and the resulting filtrate, or 

 lye, was mixed with the fats for soap mak- 

 ing. The fats contain fatty acids which 

 neutralize the lye and form a new substance, 

 soap. 



With the advance of civilization the 

 labor of soap making passed from the 

 home to the factory, very much as bread 

 making has done in our own day. Dif- 

 ferent varieties of soaps appeared, of which the hard soap was 

 the most popular, owing to the ease with which it could be 

 transported. Within the last few years liquid soaps have come 

 into favor, especially in schools, railroad stations, and other 

 public places, where a cake of soap would be handled by many 

 persons. By means of a simple device (Fig. 59), the soap 

 escapes from a receptacle when needed. The mass of the soap 

 does not come in contact with the skin, and the spread of 

 contagious skin diseases is lessened. 



FIG. 59. Liquid soap 

 container. 



