Blake — Behavior of Red Colloidal Gold Solutions. 433 



Aet. XLII. — Behavior of Bed. Colloidal Gold Solutions 

 toward the Electric Cui^reut and toward Electrolytes ; by 

 J. C. Blake. 



[Contributions from the Kent Chemical Laboratory of Tale University — CXXII.] 



I. Behavior toward the Electric Current. 

 It is generally stated that colloidal gold solutions,* as well 

 as permanent snspensionsf and solutions of typical colloids, 

 such as egg-albumen,:}: are coagulated and precipitated by the 

 passage of the electric current, red colloidal gold solutions 

 being simultaneously turned blue. I have investigated the 

 behavior in this respect of completely reduced red solutions of 

 colloidal gold, formed by the action of an ethereal solution of 

 gold chloride dried at lYO" on acetylene Avater containing ether.§ 

 Such solutions contained in an ordinary beaker are apparently 

 unaffected by the passage of the current for hours between 

 gold or platinum wires 1""°^ in diameter at a potential diiference 

 of 110 volts, unless, owing to the proximity of the electrodes, 

 enough chlorine is liberated from the hydrochloric acid present 

 to attack the colloidal gold with the foi'mation of a solution of 

 gold chloride from which ordinary gold is deposited on the 

 cathode. This apparent inactivity toward the current is due 

 to the fact that the conditions favor uniform diffusion of the 

 gold throughout the liquid. When, on the other hand, the 

 colloidal gold solution is contained in an ordinary IJ-tube, with 

 an electrode in each arm, barely entering the liquid in order to 

 avoid the diffusing effect of the escaping gases evolved by the 

 current (amounting to about 0*005 ampere under the given 

 conditions), electrical migration and concentration of the gold 

 may be observed. Under these conditions, when contact is 

 made, the gold immediately begins to settle from around the 

 cathode with a clear surface of demarcation, leaving a color- 

 less liquid, but never j)assing the bend of the U-tube; the 

 gold solution around the anode grows deeper in color for about, 

 half an hour and then grows lighter in color, until aftertwelve 

 hours or more only a faint pink tint remains, all the gold 

 being now concentrated in a red cloud at the bend of the 

 U-tube except for a slight deposit of dark-colored slime on the 

 anode. When the U-tube was so constructed as to have a 

 long horizontal portion between the two arms, the phenomena 

 were unchanged, the red cloud forming midway between the 



* Zsigmondy, Lieb. Ann., ccci, 29; Bredig, Anorganische Fermente, 

 Leipsig, 1901, p. 28. 



f Spring, Eec. trav. chim, Pavs. Bas., xix, 215. 

 X Hardy, Jour, of Physiol. , xxiv, 292. 

 § Cf. this Journal, xvi, 381. 



AM. Jour. Scl— Fourth Series, Yol. XYI, No. 96.— December, 1903. 

 3U 



