the propertie- of tlu- -olution. In -onie o>ll. idal solutions the 

 particle- an.- positively. in other- nei/ativcly charged. The chemical 

 behavior <>f the colloid is largely determined by the sign of the charge 



'ii ihe particle-. 



A. SUSPENSK >X C( >LL< >II>S (SUSPENSE >IDS). 



MX.. The colloid- to be -tudied are ferric hydroxide (positive) 

 and arsenious sulphide i negative). I 'roceed as to]lo\vs: 



a. Xote the phvsical properties (optical properties, vi-cosity, difiu- 

 -ion in ]ure solvent, filterability) ; diffusion through collodion mem- 

 liraiu s. 



I',. Action of non-electrolytes. To 3 cc. of each solution add its 

 volume of m-sugar -olution. l\e-ult? 



C. Action of electrolytes. Ion action. l/sing 3 cc. of ferric 

 hyilroxidc hydmsol in each experiment, add six drops of each 

 of ihe following -olution-. Shake gently and note the result care- 

 fully in each case. 



a. n jo I If!, n 20 !!><>,. n 2O H 3 PO 4 or n JO H 8 C 6 H 5 O 7 

 ( citric acid ). 



b. n, 20 XI l,i) 1 1. ,, 20 KOH or NaOH, n 20 Ba(OH) 2 . 



c. m _'o Xa('l. in jo Xa._.S< >,, m Jo Xa .. citrate. 



d. m jo Xai'l.ni 2O CaQ 2 , rn 20 A1C1 , 



M>-. Repeat this series with arsenious sulphide hydrosol. \\iiat 

 (litTerence^ do you (hid in the action of the acids, ba-cs and -alts upon 

 the tw hydrosols? What relation- do yon find between ^rcci^itnt- 

 Inij / i (Ti'(T and :<//('//(( of the ion- of the electrolyte? Which ion- 

 precipitate the positive and which the iu-</dti:'c colloid? Explain. 



||<S. Mix e<|iial \-olume- of the two hydro-ol-. Any result? 

 Explain. 



' 



EMULSION COLLOIDS UK HYDROPHILOUS COL- 

 l.( )II)S i EMULSl )IDSi. 



In tin- cla-s of colloidal -oluti ns the union with the -oKrnt 

 (water) i- more intimate. The-e colloid- incorporate or combine. 

 water spontaneously ; the colloidal particle- are thus probably water- 

 -\\olK-n or liydrati'd. and hence not SO -har|>ly separated I nun the 

 medium a- in the -u-pen-oid hy<lro-ol-. Their -ohition- are more 

 like cry-talloid solution-, and the condition- of precipitation from 

 -ohition are different from tho-r -lio\\n 1>\ -u-pen- 'ids. 



-J-' 



