Thanks Ian. The bottom line, for those interested is that Azo paper is an AgCl/I emulsion, not purely AgCl as some have claimed.
Also, some added notes are in order. Please look again at the Azo type formula I posted and see that the iodide is added AFTER precipitation. This type of control does not normally work during or before precipitation!
Also note that Cadmium salts work poorly if at all in bromide only emulsions. And, note that Cadmium salts are used at much higher levels than most other salts for contrast control. They work to increase contrast by another method. Cadmium salts sharpen or 'scoop out' the toe of the emulsion thereby raising contrast.
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