150 ORIGIN AND NATURE OF LIFE 



somewhat extensively for commercial preser- 

 vation of eggs. If dilute acid be added cau- 

 tiously to this substance silicic acid in a 

 water-soluble form is produced. If a solution 

 of this silicic acid be placed in a tube made 

 of parchment paper (such as is used for cover- 

 ing jam-pots), and the tube be suspended in 

 a stream of running water, the solution may 

 practically be freed from the excess of acid 

 used for its manufacture and from other 

 impurities. 



This was the method by which Graham 

 first prepared colloidal silicic acid, and by 

 somewhat similar methods, he also prepared 

 a large number of other inorganic colloids 

 in clear solution, and demonstrated that so 

 far from being exceptional amongst inorganic 

 molecules, the colloidal state is one of frequent 

 occurrence. 



Such colloidal solutions of inorganic bodies 

 exhibit all the delicate properties described 

 above, in regard to coagulation, etc. 



Graham showed that the silicic acid solution 

 behaved in all its chemical properties as if 

 it had a multi-molecule, consisting of about 

 sixty molecules instead of one, united into 

 one chemical unit. 



It still behaved as an acid, but a given 

 weight of it only required about one-sixtieth 



