Science Buddies: "Ask an Expert"

For my science project i am finding out the buffer capacity of local waters. i plan to 'pollute' water samples with hydrochloric acid, i am wondering what type of hydrochloric acid will i want to use?

I am a little confused by the question. As far as I know there is only one type of hydrochloric acid available. If you are thinking about purchasing the acid I would use whatever grade I could get for the cheapest. You will not need a laboratory grade acid with all impurities removed for your experiments. The most concentrated form of this acid you will find is 35%. I doubt that you can purchase this any more with the new regulations in effect.

A warning here. Unless you are very familiar with acids do not use this by yourself. Hydrochloric acid is the second strongest acid available. The only thing stronger is hydrofluoric acid. Hydrochloric acid must be used safely. It an burn you very badly and I have seen cases where it burned a person's arm down to the bone underneath. You must have very good ventilation because one of the byproducts is chlorine gas, which is also deadly. I would strongly recommend that you ask your Chemistry teacher to help you when using this acid. They will have access to the safety items necessary when using this acid. You must have ventilation, acid resistant gloves, breathing protection, eye protection, and clothing protection. A couple of years ago two people were killed in my city when they added hydrochloric acid to drinking water at our local water plant and they were supposed to be trained on how to use it.

Your teacher can help you make varying concentrations of the acid that you can add into set amounts of the water that you are trying to pollute. Remember to always add the acid to the water you are trying to pollute. Add the acid slowly and if you get too much of a reaction wait until it cools down before adding more.

I hope this answers your question. If not please let me know and I will try to explain better.