First of all, Merry Christmas everybody!

Just a quick question:  What color is pure sulfuric acid?  Wikipedia tells me it's clear and colorless, but maybe that's just an approximation?

I got some from a hardware store, and it's an oily brown color.  It's concentrated enough that it doesn't eat metal very much unless you add water.

But got some "battery acid" today, and it's pretty clear, but not nearly as concentrated.  (It doesn't even boil the water you add it to.)

So is the hardware store stuff impure, or is the battery acid version too dilute to show the color?

BTW, what is the scooby snack thing?  Is it one of those reputation systems, where I give a snack to somebody who helps me?

Yes, pure sulfuric acid should be a completely colorless, oily liquid.  As has been mentioned already, numerous contaminants can make it seem yellowish or brownish.  Especially if those contaminants are organic in nature.

I also noticed in your post that you talked about adding water to an acid.  PLEASE don't do that.  ALWAYS add a concentrated acid to water and not the reverse.  Many people underestimate the amount of heat generated when a concentrated acid is diluted, and if you're not careful you may wind up with a face full of concentrated acid.  (As the water instantly boils and sprays the acid up in a steam explosion).  Even if you're confident in what you're doing, it's always best to make it a habit to add the concentrated to the dilute.  

Also, "concentrated" is a vague term.  I was looking at some HCl at the hardware store the other day and it was only like 60% or so...don't remember off the top of my head.

In case of sulfuric acid "concentrated" means usually about 96-98%, as that's how it is sold.

HCl you have seen was not 60%, as HCl can't be made more concentrated than about 40%.

If I may ask, where might I find the FAQ?  All I found was the forum rules.

Oh, sorry. I forgot, they're under "help."  The link to help is on the green bar underneath the Chemical Forums logo.