In situations in which two different waters are being mixed, it is desirable to measure the amounts of each in the mixed stream. If the capability exists, it is desirable to look at each constituent to see if it undergoes any phenomenon other than simple mixing. This can be a powerful technique for detecting water/rock reactions that can lead to formation damage. The fundamental concept is that mixing two waters should result in the volume-weighted average of each constituent of the two original waters, unless some chemical or biological reaction occurred. This is essentially similar in appearance to a binary phase diagram, with the endpoints of the line defined by the concentrations of the constituent in each of the water streams being mixed.