Here's where things get fun. Just like the number of reps, 3-6 sets is the best range of volume for this training method. If you like your workouts paced like clockwork, take 30-60 seconds rest between each exercise.
The natural attraction between positive and negative keeps the ions surrounded by water molecules and therefore dissolved in solution. Many biochemicals are either polar molecules or charged ions (or both) so water makes an excellent solvent for them.
Yes, ammonia is highly soluble in water. It is, in fact, more soluble than any other gas in water. 100 ml of water can dissolve as much as 31 gm of ammonia at 25 degree celsius. A solution of ammonia in water is called ammonium hydroxide, NH4OH. Ammonia's high solubility in water is due to hydrogen bonding with water molecules.