I 01 



ince in ill" properties of a colloidal Bolutioi 

 rion of the Bame Bubstance l • 

 Bolution of platinum | prepared by al 



• ••■II platinum electrodes in and p im in 



depends on the fad that the bu tinum in I 



has I n increased many million times. When th< 



still greater and the particles gain the bu 



due to Burface development become Bup] 



centration in unit volume become tuated '!"■ ■■ 



cut t.n osmotic pressure, difrusibilitj 



whether ions, molecules or particles, but 



much more pronounced when the die 



and others when they are small. In other words, the pi 



surface, such as those of surface tension bcc p 



only when the dispersoids have the properl in ma 



the dispersoids 1 me molecular in size, they manifest tl 



characteristic of true solutions. 



4. Electric Properties of Colloids, fcfosl colloids carry i which 



may be either positive or negative toward the dispersion medium. B<>th 

 crystalloids and colloids therefore carry 



case, however, the charge does not reveal itself until the mol 

 solution have become dissociated, when each ioi of 



opposite Bign (see t »;i >_-•.• 16), whereas in the 

 loid particle usually carries a charge which is alwi 

 positive or negative. Colloids may ther< 

 and negative, according to the charges which tin 

 a third group in which the charge may be eith< 

 cording to the nature of the dispersion medium. 



A colloid not carrying a charge to begin with can b< 

 by the action of electrolytes, for I 

 aa well as those of inert powders ended in in- 



fluenced by the charges present in the i"iis of tl I urn. 



The II- and < >H' ions an •daily liab 



particles of inert powders in bus] 



a positive charge when the water in \\h 



Bed, and a negative charge when i1 is mad< alkali] I 



be said that suspensions st po\> 



in w ater • g eha coal, cellulos 



• »r congo red, etc. are •■ 



ide l ferrum dialysatum and Berum ; 



tioi senious Bulphide at 



Bolution, and strum globulin in n< I 



