# How to determine the amount of barium in a sample of contaminated water?

Here is the assignment I have:

You are working for Matrix Pro - a company involved in analytical assessment and method development for the clean-up of contaminated waters.

You received water samples from a potential client. The samples may contain the following ions: $\ce{H+, Ba^2+, OH^─}$

The potential client requested a qualitative analysis of the sample as well as the development of a treatment technique that will bring the pH value to neutral and eliminate the barium ions. For comparison another water sample (considered to be non-contaminated) was also sent for similar qualitative analysis.

Assignment

1. Develop an experimental procedure to comply with the request of the potential client.

2. Draw a flow chart.

3. Tabulate all your observations and data.

What I'm not sure about is finding the amount of barium present in the unknown sample so I can determine the amount of precipitating reagent to add. I just want to know what type of analysis to do. Chromatography? Spectrophotometry? Something else?

• You could add some sodium sulfate solution to a sample of the water to see if barium sulfate precipitates. It wouldn't be difficult or expensive to do this quantitatively for that matter. – airhuff Apr 11 '17 at 2:01

If a gravimetric analysis does not provide the detection limit required by the client, the next best options are atomic absorption spectroscopy (AAS) and inductively coupled plasma - atomic emission spectroscopy (ICP-AES). As these analyses can be done very cheaply (~\$10-$30 per sample) you may actually want to do this to begin with. The down side of outsourcing is that the turnaround time could be weeks, or the price could quadruple if you need results fast.
• Gravimetric analysis of $\ce{Ba^{2+}}$ was one of the practice exercises in my quantitative analytics lab. We had to use filter crucibles because $\ce{BaSO_4}$ is usually very fine-grained and to allow for heating at 900 K for several hours to remove water. – TAR86 May 4 '17 at 19:17
• @TAR86 , My first response is: 900K ?! I guess that would get it dry in a hurry. The way I've described it is basically an ASTM standard method that my lab has probably done thousands of times over the years. So long as there is sufficient $\ce{Ba^2+}$ in solution, gravimetric analysis can actually give much better precision that AA or particulary ICP. – airhuff May 4 '17 at 19:31