Sal ammoniac is mentioned in the earliest alchemical work I know of. I recall a recipe to make it but there must have been uses for it.

The best ammonia experiement I know involves the gas.

You could probably find some fun experiments by googling for “chemistry magic trick ammonia”.

Regarding natural ph indicators, I always used baking soda or dilute lye/drano as the basifier, except for the blueberry pie a’ la mode:

Blueberry pigment like most natural organic pigments acts as a ph indicator by changing color. In a regular pie, the filling is acidic enough to make the pigment a bright reddish purple. Mix the filling with a little melted ice cream, and the ph is lowered enough to change the pigment to a dark blue-ish purple. Then you can break out the vinegar and baking soda.

Another interesting experiment is to examine how pigmented food items react to ph changes. Artifical colorings tend not to change color, while natural ones tend to do so. For example, do cheaper liqueurs tend to use artifical coloring to mimic the natural color of their more expensive counterparts?

A warning about nitrogen tri-iodide: It is extremely unstable when dry. Extremely!!!! Even a slurry of crystals and solution is stable but when dry watch out. The good news is you probably won’t have enough to do real damage, but once it is dry you can’t even touch it. A fly landing on it, a dry filter paper floating gently to the ground, etc. are all way too much disturbance. Plus, there are the stains. If you MUST play with it, keep it wet, preferably in solution and be aware that crust can form around edges and rims and in / on nozzles. Apply it as a solution and allow to dry. Dispose of the solution when done; if you store it and it dries out you are in a fix.

You can find out more by following this link (Nitrogen Triiodide)

http://www.armory.com/~spcecdt/pyrotech/ni3_dir.html