438 Blake — Behavior of Red Colloidal Gold Solutions. 



about the change of color if it is the haphazard coincidences 

 of gold particles and basic ions which condition the transfor- 

 mation, rather than some uniform and sudden change through- 

 oat the entire liquid, such 'as would be indicated by the 

 observations of Bodlander on the coagulation and precipita- 

 tion of kaolin suspensions. 



That the effect of mixing two electrolytes whose basic ele- 

 ments have different valencies is subtractive rather than addi- 

 tive was shown by Linder and Picton* for colloidal solutions 

 of arsenious sulphide and by Hardyf for colloidal solutions of 

 egg-albumen, and is indicated by the following experiments, 

 in which a red colloidal gold solution containing a known 

 amount of a salt of a univalent basic radical was titrated to 

 the violet color by barium chloride. 



Table II. 



Vol. of 



gold 



solution. 



Electrolyte No. 1. 



Amt. 

 of el. 

 No. 1. 



Final 

 cone, 

 of el. 

 No. 1. 



Elec. No. 2. 



Amt. 

 of el. 

 No. 2. 



Final 

 cone, 

 of el. 

 No. 2. 



em^. 





em^. 







cm^ 





50 



^-NH,N03 



65 



•052 



^-BaC, 



9^2 



•0074 



100 



ii-NaCI 



100 



•047 



{o-^^C"' 



14-5 



•0068 



50 



[Average from Table I.] 



! n 



— -Bad, 

 1 10 



3-Jl 



•0058 



It seems impossible to reconcile these results w^th Whetham's 

 hypothesis. It is evident that a quantitative study of the 

 effects of mixtures of electrolytic substances in various pro- 

 portions in turning red solutions blue offers an interesting 

 field for the investigation of the properties of electrolytes 

 themselves. 



It was thought likely that the remarkable stability of these 

 red colloidal gold solutions was due to the ether present, act- 

 ing as a non-electrolyte in inhibiting the action of electrolytes 

 after the fashion of typical colloids, such as gelatine — a phe- 

 nomenon first pointed out by Faraday,^ -"tnd applied by Lotter- 

 moser and Meyer,§ Zsigmondyl and others. Consequently the 

 following experiments were made on the same gold solution 

 used above, but diluted with four volumes of water. To this 

 diluted solution various amounts of ether were added before 

 titration. The results are given in the following table. 



* Jour. Chem. Soc, Ixvii, 63. f Jour, of Physiol., xxiv, 182. 



tPMl. Trans., cxlvii, 145. § Jour. Prakt. Chem., Ivi. 248. 



II Zeitsch. Anal. Chem., xl, 697 ; Schulz and Zsigmondy, Hofmeister's Bei- 

 trage, iii, 137. 



