Hydrochloric Acid For Identifying Rocks - I Know, I Know...not Really Fossil Related. :)

[Geo Dust]

Does anyone know where I can buy some dilute hydrochloric acid for identifying rocks without ordering online?

I'm taking my daughter fossil hunting this summer and at the same time, I going to teach her how to identify rock types, so, I'm hoping to show her how carbonate rocks will effervesce when in contact with the acid.

Thanks in advance!

[Auspex]

Home Depot, etc...

"Muriatic Acid" is dilute hydrochloric.

[Seldom]

Hardware stores have it by the gallon. If you just need a few oz ask your plumber he might have some he uses to unstop drains in older cast iron pipes.

[JohnJ]

Dusty, you can get the same effect and lesson, much safer, using vinegar (acetic acid).

[tracer]

please mark my vote down in big giant black sharpie for vinegar...

the muriatic acid at the store comes in too big an amount and is too strong.

vinegar fizzes nicely on the cretaceous limestone i've put it on.

[Geo Dust]

Yep - you guys are right. The amount you get from home depot is just too much. I don't need two gallons of muriatic acid laying around the house.

I went outside and tested some vinegar on limestone - and you're right - it works. I think I'll just use the vinegar. Thanks for the suggestion!

[Acryzona]

I agree with the vinegar idea (~5% acetic acid). On a related note, does any know where to purchase say 10% acetic acid in bulk. I want to dissolve several pounds of limestone to extract conodonts this summer. Many of the chemical supply business will not sell to me as I'm not a business nor an educational facility.

[jkfoam]

Home Depot, etc...

"Muriatic Acid" is dilute hydrochloric.

Auspex, Muriatic acid is Hydrochloric acid, but it is not dilute hydrochloric acid it is concentrated hydrochloric acid. Dilute hydrochloric acid is generally considered to be about 5 Wt % HCl in water. Muriatic acid is about 35 Wt, % HCl in water, the same as concentrated hydrochloric acid. At one atmosphere of pressure and about 20 Celsius this is about the most HCl that will dissolve in water.

JKFoam

Edited June 10, 2010 by jkfoam

[Auspex]

Auspex, Muriatic acid is Hydrochloric acid, but it is not dilute hydrochloric acid it is concentrated hydrochloric acid. Dilute hydrochloric acid is generally considered to be about 5 Wt % HCl in water. Muriatic acid is about 35 Wt, % HCl in water, the same as concentrated hydrochloric acid. At one atmosphere of pressure and about 20 Celsius this is about the most HCl that will dissolve in water.

JKFoam

Wow; my bad

Good catch.

[ashcraft]

I agree with the vinegar idea (~5% acetic acid). On a related note, does any know where to purchase say 10% acetic acid in bulk. I want to dissolve several pounds of limestone to extract conodonts this summer. Many of the chemical supply business will not sell to me as I'm not a business nor an educational facility.

Look for "glacial acetic acid", which is 100% acetic acid. Be warned, it has a most impressive "wang" of a smell. I pass the cap around in chem I, to show them how to waft scent. There is always some boy who is going to show his manhood by snorting it. Some have actually thrown up. A good demo on the stupidity of the teen age boy.

Glacial acetic acid is also flammable, under certain conditions.

If you are going to dissolve large chunks of limestone however, it will be much cheaper to use muriatic acid. Be sure to do it in a plastic container and outdoors, downwind of any buildings. HCl gases chlorine gas, which isn't particularly healthy for a living organism. After dissolution in the Hcl, the conodonts are usually separated by density from the residuum, but I don't remember which chemical is used.

There is a journal article that describes the procedure, "conodonts of the Dutchtown Formation" or something similar. I'll have to check it out when I get home.

Brent Ashcraft

[cousin it]

Yep - you guys are right. The amount you get from home depot is just too much. I don't need two gallons of muriatic acid laying around the house.

I went outside and tested some vinegar on limestone - and you're right - it works. I think I'll just use the vinegar. Thanks for the suggestion!

Unless you want to prep some silicified fossils. It goes pretty quick, and is relatively benign... if you have half a brain, but there are some nasty consequences. So,... awwww never mind; stupid should hurt!

EDIT: If working with Hydrochloric Acid(HCl), be sure to follow ALL safety protocols in the MSDS. If working with HCl, read this... it is the MSDS, and it is important!

http://www.micaprintmaking.com/wp-content/uploads/msds/hydrochloric_acid.pdf

Edited June 12, 2010 by cousin it