574 Dr. W. C. McC. Lewis on the Energy of a 



of the same order for his colloidal metal preparations, though 

 these more frequently belong to the order 10 -6 to 10 " 7 cm. 



Liqui 



d Medium— Distilled Water. 



Disperse phase. 



Velocity in cm. /sec. 



under a gradient 



1 volt per cm. 



P.D. ofthe 

 particles 

 in volts. 



Observed by 



Arsenic sulphide 



22X10" 6 



-0-032 



Linder & Picton*. 



Quartz (suspended) ... 



30x10"° 



-0 044 



Whitney & Blake t 



Hydrocarbon oil ..>.... 



43xl0" 5 



-005 



Lewis J. 





40X10" 5 



—0058 



Whitney & Blake. 



Gold 



40X10" 5 



-0 058 



Platinum 



30x10"° 

 21-6x10"° 

 20-3 xl0~ 5 



-0 044 

 -0-032 

 -0-030 



Burton §. 

 >> 



Gold 



Platinum 



Silver 



23-6X10" 5 

 30x10" 



-0034 

 +0-044 



>> 

 Whitney & Blake. 

 Burton. 



Iron hydroxide 



Bismuth (hydroxide) .. 



nxio" 5 



+0-016 



Lead (hydroxide) 



12xl0" 5 



+0-018 



>> 



Iron (hydroxide) 



19xl0"" 5 



+0-028 



>j 





* Linder & Picton, Journ. ofthe Chem. Soc. lxxi. p. 568 (1897). 

 t Whitney & Blake, Journ. Amer. Chem. Soc. xxvi. p. 1339 (1904). 

 t Lewis, Zeitschriftfur Kolloide, iv. p. 211 (1909). 

 § Burton, Phil. Mag. xi. p. 425 ; xii. p. 472 (1906). 



The most important fact about the above values for the 

 P.D. of the particle is that they are all of the same order of 

 magnitude. There appears to be an entire absence of ary 

 specific effect due to the chemical composition of the disperse 

 phase. This is brought out more clearly when instead of 

 altering the nature of the disperse phase we alter the medium, 

 as was done by Burton (I. c). 



Medium. 



„ * x 



Ethyl Ethyl Methyl 



Disperse phase. Water. malonate. alcohol. alcohol. 



Platinum —0-03 volt -0 054 



Gold -0032 -0-033 



Silver ! -0034 -0040 



Lead (hydroxide) +0'018 +0023 +0*044 



Bismuth (hydroxide)... +0*016 +0*022 



1 think one is justified, in view of the above figures, in 

 saying that the P.D. of particles in colloidal solution is in- 

 dependent of the chemical nature of both the disperse phase 

 and medium. 



