Blake — Comjposition of JBredig^s Silver Ilydrosols. 431 



Art. XLI. — I^ote on the Composition of Bredig^s Silver 

 Ilydrosols ; bj J. C. Blake. 



[Contributions from tbe Kent Chemical Lab. of Yale University. — CXXI.] 



In preparing silver hydrosols by passing the electric spark 

 between silver electrodes under water according to the method 

 of Bredig,* it was noticed that the anode was eroded fully as 

 much as the cathode, especially if the current passing was 

 small (four amperes) ; and the freshly prepared liquid was 

 always distinctly alkaline. The black deposit which at first 

 settles out was dried at 105° or at 140°, and found to lose 

 weight on ignition. The alkalinity of the liquid and the loss 

 on ignition of the deposit were attributed to the presence of 

 silver compounds, formed by oxidation of the anode. Some 

 silver solutions obtained by the action of the current without 

 sparking led to a confirmation of this belief. 



Electrodes of specially purified silver consisting of plates 

 Q.gmm \\YiQk aud 3""°^ wide, and of convenient length, as well as 

 electrodes of silver wire obtained in the market, were immersed 

 one or two centimeters in water from a tin still, or in " con- 

 ductivity " water, and connected with the street current having 

 a voltage of 110. On placing the silver electrodes in the 

 water white and yellowish clouds seemed to arise from them 

 and disseminate throughout the liquid, although the electrodes 

 were some centimeters apart. This phenomenon, investigated 

 in open vessels and in U-tubes plugged with asbestos, gave the 

 following results : 



Conditions, 

 111 an open vessel. 



In an open vessel, each 

 electrode surrounded by a 

 filter paper. 



In a TJ-tube, electrodes sep- 

 arated by two loose asbestos 

 plugs. 



In a U-tube, electrodes sep- 

 arated by two tight asbestos 

 plugs. 



Time, 

 hrs, 



Distance 



between 



electrodes. 



cm. 



Erosion 



of anode. 



grm. 



2* 

 2 



2 to 7 



2 



00821 — 

 0-0692- 



0-0655 



2 



2 



0-0149 — 



7 



4 



0-3107 — 



3 



3 



0-0488- 



9 



3 



0-0184 — 



Throughout these experiments the cathode remained 



unchanged in weight, although a yellowish gray slime of 



* Anorganische Fermente, Leipsig, 1901. Zeit. Angew. Cbem., 1898, p, 

 951. 



