USES OF SAPONINS i8i 



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 is 

 indicated in the name Saponin itself and also by the names 

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



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

 saponis indici) and these, as well as the beans of Entada 

 scandens and LycJmis 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 delicate 

 fabrics. 



Aqueous solutions of saponins have a marked power of 

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

 this reason saponins are occasionally added to effervescent 

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

 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. Concentrated 

 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 and 

 require a small quantity of alkali to enable them to dissolve 

 completely. 



For their aqueous solutions saponins may be precipitated 

 unchanged by the addition of ammonium sulphate. 



In the form of lead or barium compounds they may be 

 precipitated from aqueous solutions by the addition of either 

 lead acetate or basic acetate of lead or by means of a solution 

 of barium hydrate. 



The saponins are almost all insoluble in absolute alcohol, 

 ether, chloroform and benzene. 



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

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

 lytic action (see p. 182) being only very slight. 



