Science Buddies: "Ask an Expert"

I need help figuring out the % of copper ion in a solution of copper sulfate called Aquari-Sol. It is a product used for treatment of protozoan and Ick in aquarium fish. The MSDS sheet from the company says it contains 0.000125 mg/ml copper sulfate. It also says it contains 1 - 2.5 % copper sulfate in solution. I need to know the % copper ion in it. I want to mix solutions starting at .2 ppm and going up to 1.0 ppm. Thanks for your help.

Hi,

This is an interesting chemistry question. 1 ppm is equal to 1 mg/liter. Copper sulfate has a molecular weight of 159 g/mole and copper is 65 grams/mole. Please let me know if the following makes sense to you or not, because I know you have not had a lot of chemistry yet. I will explain more, if needed.

If the solution contains .000125 mg copper sulfate in 1 ml, then multiply this by mM/159 mg to determine the number of moles of copper sulfate. This is equal to .0000075 mM copper sulfate per ml. Then multiply this by the molecular weight of copper (65), to determine the weight of copper in the solution, or .000049 mg/ml or .049 mg/liter or .049 ppm.

However, the MSDS says that the product contains 1-2.5% copper sulfate so this would be equal to 1 to 2.5 grams per 100 ml, or 10 to 25 grams per 1000 ml, or 10 to 25 ppM. So the .000125 mg copper sulfate per ml must refer to the effective concentration after dilution. The directions for using the product specify using 1 ml in 18 gallons which is equal to 1 ml in 68 liters or a 1:68,000 dilution. If you multiply .000049 mg/ml by 68,000, this would be 3.3 grams/mL, which is higher than stated in the MSDS. I can’t tell you how to dilute to get a .2 ppM solution until we know what the real concentration of the product is.

So there is a discrepancy in the information provided by this company.

The exact concentration of copper sulfate in the product is probably proprietary, but perhaps you should contact them and explain that you are doing a science project and ask if they will tell you what the concentration of cupper sulfate in the undiluted product is. Otherwise, let me know if you can find another source of copper sulfate, or if you want to try analyzing the copper to find out the concentration. Let me know if you have access to a spectrophotometer.

http://genchem.rutgers.edu/cuanal.html

You could do a whole project just figuring out how much copper is in this product.

If you want to assume that the product contains 2 % copper sulfate, this would be equal to .8% copper (2 x 65/159), or 8 grams per liter, or 8 ppm copper. With this information, can you now figure out how to dilute to the concentration you want to use for your experiment? Let me know if you need more help.

Donna Hardy

Hello again,

I am checking back with you because I am always concerned when I explain the chemistry of a topic and don't receive any questions back. I hope that I didn't overwhelm you with too much information. Please let me know if you need a simplified explanation. I hope you were able to proceed with your project. Please let me know if you have any questions.

Donna Hardy