[Jordanpogo]

I've hit Day 2 of a brain block on this, so I decided to hit the forums for some help.

Basically, I can't figure out how in the world the TDS calculated is 258.

The TDS simple summation was easy to calculate, adding all of the concentrations.

To get TDS calculated I attempted this formula,

TDScalc=TDSsum-[HCO₃^--{Mg²⁺+(Ca²⁺-So₄^2-)}]

TDScalc=391-[130-{135+(30.5-131)}]=295.5

295.5≠258!!!!!!

I feel as if the alkalinity has something to do with the answer but I have no idea how to include those values.

There is an EC column that has been completely unused in the assignment so far so I have an inkling that this value could also be useful.

Also, my professor has the Mass Balance (%) at 13, but I have written in my notes that Mass Balance = TDSmeasured-TDSCalculated which would be,

391-258=133.

Below is an image a picture from my lab.

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[img width=800 height=600]http://i67.tinypic.com/k4dyj5.jpg[/img]