182 



GLUCOSIDES 



substance obtained from the root of Saponaria rubra and 5. alba 

 is now applied to a large group of compounds, all of which 

 have properties similar to those possessed by the original 

 saponin. 



General Properties and Uses of Saponins. 



The saponins are mostly amorphous colloidal substances 

 which dissolve readily in water ; their aqueous solutions, 

 shaken up alone, produce a froth, but if shaken in the presence 

 of oils, fats or resins, they produce emulsions which are charac- 

 terized by their great stability. 



Connected with their emulsifying property is the employ- 

 ment of saponins as substitutes for soaps, a fact which 

 indicated in the name Saponin itself and also by the name 

 Saponaria, soap wort and Quillaia (meaning wash wood), etc. 



The so-called soap nuts are the fruits of Sapindus (fructus 

 saponis indici) and these, a well as the beans of Enlc 

 scandens and Lychnis chalcedonica or Tartary soap, are largely 

 used in the East for washing clothes, since they have no de- 

 leterious effect on the colour or the fibre of the most delicat 

 fabrics. 



Aqueous solutions of saponins have a marked power ol 

 retaining dissolved gases, as, for example, carbon dioxide ; fc 

 this reason saponins are occasionally added to effervescent 

 drinks, such as ginger-beer or lemonade, a use which is to 

 deprecated owing to their toxic properties.* 



Occasionally saponins are employed for making suspensions 

 of solids in water since they exert an inhibiting effect on the 

 precipitation or deposition of suspended solids. Concentrate 

 aqueous solutions of the saponins have adhesive properties. 



Solubility. 



The saponins are, as a rule, neutral substances which dis 

 solve readily in water, but a few are acid in character an< 

 require a small quantity of alkali to enable them to dissob 

 completely. 



* The saponin obtained from the bark and wood of Guajacum officinale h 

 occasionally used for this purpose since it is practically non-poisonous, its haer 

 lytic action (see p. 183) being only very slight. 



