378 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



Experiments have also revealed the fact that the finely 

 divided particles present in a colloidal suspension often bear an 

 electric charge — a charge which causes the particles to mutually 

 repel each other and hence acts to prevent the precipitation of 

 the particles. It is often possible to discharge these particles 

 with the result that they will then precipitate and this principle is 

 turned to practical account when, for example, it is desired to 

 cause the precipitation of finely-divided solids suspended in 

 water. 



In discussing colloids, however, we have to deal not only 

 with the colloidal suspensions known as "sols" but also with the 

 solids known as "gels" which are formed by their precipitation 

 or by the setting of the liquid when cooled. Mere mention of 

 the fact that many of the questions connected with the processes 

 of dyeing, of tanning, of purification of sewage, of the working 

 of rubber are questions pertaining to the character of colloids 

 shows something of the importance of this subject in the indus- 

 trial world. Some of the most important constituents of the soil 

 are colloids and the application of the principles of colloid chem- 

 istry to this study has been of great service. Finally in the study 

 of biology we are often dealing with questions connected with 

 colloid chemistry. 



The Synthesis of Organic Compounds. Among the impor- 

 tant problems that present themselves in the field of Organic 

 Chemistry is that of gaining some insight into the structure and 

 properties of those carbon compounds that appear to be most 

 closely associated with the life of the organism ; also, the problems 

 of ferreting out nature's way of building uj) the compounds, 

 often highly complex, that are found in the living organism. 

 The problem is as difticult as it is alluring and not much progress 

 has been made. It is true that chemists have succeeded in 

 synthesizing some of these compounds, I)ut it is certain that the 

 methods used by chemists in accomplishing these syntheses are 

 not the methods which nature employs. The chemist uses high 

 temperature, strong acids and alkalies, and conditions that would 

 at once destroy the life of any organism and put an end to it.s 

 synthetic powers. Nature accomplishes the same end working 



