[jgrant]

Hello.

I'm a physicist whose knowledge of Electrochemistry is limited to say the least.

I'm currently in need of information regarding Ag/AgCl reference electrodes on CMOS chips.

My current plan is to evaporate 500 nm Ag and then place the CMOS chip with the evaporated Ag into some chlorine containing solution. My questions are these:

What is the best Cl solution fo form AgCl? I've read papers saying that FeCl3 is best (but they dont state why). Intuitively you would think that a solution of AgCl would be best. Note that this despoition of AgCl is purely passive, there is no potential applied to the evaporated Ag electrode.

Finally I'd like to produce some AgCl solution. I have purchased AgCl in solid form. What should I dissolve the AgCl into and what should the ratios be?

Many thanks.

[Arkcon]

AgCl is very insoluble in water.  As I understand the Ag/AgCl electrode, it's an "alloy" of silver and silver chloride {silver chloride can be fused, and tooled or machined as if it were a metal) and the electrode immersed in a solution of some other, soluble chloride.  To provide come Cl- anion I would use just about any chloride, NaCl is cheap, KCl is a tiny bit more soluble, HCl is used also.  But there is little, to no, AgCl in solution. 

Silver does from a complex with ammonium, so as you add NH₄OH, you gradually precip. Silver Oxide, until you add a great excess, then you'll have a solution of the silver ammonium complex, [Ag(NH3)2]+, and the counter ion could be chloride, but that might not be what your application requires.  What else can you tell us about your app?