Indeed, Fred is correct. I meant all Na and K halides to be included as possible examples. And, unlike glass making, the Na or K is not included in the crystal or molecule. In some cases, Cd, Sr, Hg and Pb are included in the crystal.

To continue with the halides though, there are NaBr and KBr halides used in emulsions aplenty out there as well as NaCl/Br and other mixtures. I even know of a make that uses NaCl, NaBr, and Methyl Mercuric Iodide to make a 90% Br, 9.9% Cl, 0.1% I emulsion. The Mercury is also there, retained in the crystal. AFAIK, this latter make was abandoned in about 1990 or thereabouts for a better method.

Now, as for the use of Ammonia. I have said that NH4 halides are restrictive and less effective than NH4OH. I've also said that the use of Ammonium Hydroxide also can cause fog. I've also said that it has been abandoned. Well, here s the modern way:

Kettle - Gelatin, Halide salt mix (Na or K salts). Feed lines are AgNO3 and Salt in 2 lines as needed.

Begin the run. When DIGESTION is to start, add the desired amount of (NH4)2SO4 (Ammonium Sulfate) and then add KOH or NaOH solution to get a pH of about 8. Digest as desired (your time and temp) and then add an equivalent of H2SO4 to bring the pH back to the starting point! NH4 Halides and Sulfate are so ineffective at the acid pH, that you effectively turn on and then turn off the ammonia digest along with any fog. This is not only the common modern method if Ammonia Digestion, it is controllable and illustrates how acid can turn off the digestion properties of the Ammonium ion.

I hope this answers those questions. BTW, the above Acid / Base cycle is about out of date now having given way to an even newer method that we really cannot use in our home labs very easily.

Science marches on.

PE