Certain liquids behave differently than their chemical compounds suggest when mixed. Oxides containing chlorine, phosphorous, silicone, aluminum, magnesium and sodium all vary in reaction to water. In reaction to other neutralizers, these chemical substances produce atypical results. Aspiring scientists need to learn the chemical product of each substance when it is mixed with water. The seemingly simple Periodic Table of Elements provides good chemical guidance, but it is insufficient to explain chemical interactions involved in successful neutralization.
Acids carry twice the ion concentration as do bases. While this is easily factored into the process of neutralizing hydrochloric acid and ammonia, "add-mix-and-measure" trumps simple numeric calculation in order to effectively neutralize acids and bases. Add too much ion concentration, or too little, and you end up un-neutralizing a successful mix. You can avoid this by the process of titration. (Check References for a video on how to set this up.)
According to the Royal Society of Chemistry, temperature changes produce chemical changes. Put simply, if a laboratory heats up during a neutralization experiment, the chemical properties of both acids and bases may require variable mixes in order for them to neutralize each other. An equal measure of base and acid, which may normally produce neutrality, may need to be altered as an experiment progresses. Scientifically speaking, the chemist ends up chasing chemistry's tail because of fluctuating temperatures.
PH indicates the effective concentration of ions in a liquid. Pure water has a neutral pH of 7.0. Acids range in pH from 0 (HCI: hydrochloric acid) to 6.0 (milk). Bases range in pH between 8.0 (egg whites) and 14.0 (NaOH: sodium hydroxide). According to Waterloo University, acid-base "indicators" are substances whose pH content causes them to absorb neutralizers at different rates. Naturally, this influences the accuracy of a hypothetical acid-base mix. Here again, awareness and adjustment prior to experimentation are essential.