J. C. Blake— Colloidal Gold. 381 



Art. XXXIX. — On Colloidal Gold : Adsorption Phenomena 

 and AUotrojpy ; by J. C. Blake. 



[Contributions from the Kent Cliemical Lab. of Yale University — CXX.] 



E-ED and blue colloidal gold solutions have long been known,* 

 the red being changed to blue by the action of electrolytes. 

 Hence, in order to study all of the concurrent phenomena, it 

 is necessary to begin witli a red solution. All of the red solu- 

 tions heretofore described, however, have either contained 

 objectionable impurities, like the acids of phosphorus, or have 

 been very dilute and hard to prepare in stable form with 

 constant properties. I have found that a concentrated red gold 

 solution, free from all these objections, may be prepared by 

 pouring into acetylene water containing ether an ethereal 

 solution of gold chloride dried at 170°. The resulting garnet- 

 colored solution of colloidal gold is exceedingly stable, though 

 quite strongly acid. It is scarcely turbid in ordinary light, 

 but gives the Tyndall effect when a beam of light is thrown 

 into it with a lens. This solution has been investigated with 

 regard to the adsorption phenomena of the gold when precipi- 

 tated by electrolytes, an investigation attended by some inter- 

 esting observations on the apparent allotropy of gold. 



It should be rememberd that Linder and Pictonf and 

 Whitney and Ober,:j: working with colloidal solutions of 

 arsenious sulphide, have found that when such solutions are 

 coagulated by electrolytes, part of the basic radical of the 

 electrolyte is retained by the coagulum, with the liberation of 

 the corresponding amount of free acid in the filtrate. The 

 base thus retained by the coagulum cannot be washed out 

 with water. Since the suspended particles of which the 

 colloidal solutions are made up are known to be negatively 

 electrified, whereas the basic radicals or ions carry a positive 

 charge, the question arises whether the basic radical retained 

 by the coagulated colloid may not be held by reason of the 

 mutual neutralization of these charges, with the formation of 

 a chemical compound or pseudo-chemical compound, thus 

 perhaps affording an indication of the nature of chemical 

 union and proving that the phenomena of the permanent 

 suspension of solid particles in liquids and. their subsequent 

 precipitation by electrolytes are essentially electrical, as is 

 assumed.in Whetham's§ hypothesis. It was thought that the 



* Faraday, Phil. Trans., cxlvii, 145 ; Pogg. Ann., ci, 313. Zsigmondy, 

 Lieb. Ann., ccci, 29, 361 ; Zeit. phys. Chem., xxiii,'63. 

 f Jour. Chem. Soc, Ixvii, 63. 

 :}: Jour. Am. Chem. Soc, xxiii, 842. 

 § Jour, of Physiol., xxiv, 288; Phil. Mag., xlviii, 474. 



