Sciencemadness Discussion Board - Dark Sulfuric Acid

Dark Sulfuric Acid

highpower48 - 24-3-2017 at 17:01

Last summer I bought a couple 850ml 98% sulfuric acid that came plastic bottles. I haven't needed them till now and noticed when I removed them from the plastic bag and light free box that they have turned very dark, close to black. Guess my question is: Is there any issue with this acid? Pretty sure the plastic bottles are the cause. But can i use the acid as normal 98% sulphric acid?

highpower48 - 24-3-2017 at 17:46

By the way the acid came from Duda Diesel

byko3y - 24-3-2017 at 18:12

Sulfuric acid might have reacted with something. Your actions depend on purpose of the acid, it's either redistillation, destruction of organic matter by peroxide, or just use the acid as is.

AvBaeyer - 24-3-2017 at 18:43

I have purchased sulfuric acid from Duda in the past. It arrived nearly colorless in plastic bottles but started to darken after a short time. I transferred the acid to glass bottles and it has stayed nearly clear for almost 2 years. My advice is to get strong acids into appropriate glass bottles as soon as you can.

AvB

greenlight - 24-3-2017 at 20:15

I have a large HDPE container with sulfuric acid that I pour smaller amounts into a 1 litre Duran bottle. The HDPE container is a couple of years old.
I have attached a picture of the acid after it has been poured into the 1 litre storage bottle for the fridge.
Also attached, is a picture of the old stuff next to new acid from a smaller bottle brought 4 months ago.
The darkness seems to have no negative effect on the acid and the darker coloured acid works just as good as the new stuff. Just make sure it is tightly sealed in its container.

[Edited on 25-3-2017 by greenlight]

[Edited on 25-3-2017 by greenlight]

LD5050 - 24-3-2017 at 21:14

Should H2SO4 be kept in a light proof container? Does it matter? I keep mine in a clear glass jug. I distill it from drain cleaner. It comes pink but after heat is added it becomes clear even before it condenses in receiving flask.

Maybe just try heating it and I bet it will become clear...

greenlight - 24-3-2017 at 21:57

I don't think it needs to be in a light proof (amber glass) container.
I keep mine in flass bottle in fridge so there is no light anyway in there.

I used to boil down 50% sulfuric acid to obtain a higher concentration and it was clear to start and always ended up darker coloured when finished...
I think my cause is just these HDPE containers darkening it after long expsoure

XeonTheMGPony - 25-3-2017 at 05:23

H2SO4 is inert to normal light, I store my distilled in a 1L reagent bottle with a glass plug and some teflon to seal and it sits on my counter top.

http://www.alchemylabsupply.com/Narrow-Mouth-Reagent-Bottles...

As said simply ensure a good seal.

Nitric is Photo sensitive it must be stored in amber, HCl in water can be stored in clear

Texium - 25-3-2017 at 07:32

Read the title of this thread at first as "Dank Sulfuric Acid"

I have a large jug of 91% sulfuric acid in an HDPE container and it's a light brown color, but works fine in reactions where that concentration of acid is sufficient, and I try to use that for whatever I can. Where that won't work, or I don't want to risk impurities, I also have some good, clean 96% acid in a glass bottle that came from VWR. I haven't purchased sulfuric acid from Duda before, but that always seems to be the case with their stuff. It seems like they package it immediately before they send it, so if you're ready with a glass bottle when it arrives you should be able to transfer it before it pulls anything out of the plastic.

Jstuyfzand - 25-3-2017 at 08:14

Quote: Originally posted by zts16

Read the title of this thread at first as "Dank Sulfuric Acid".

Wrong part of the internet!

Melgar - 25-3-2017 at 10:54

The dark color is usually from the lining underneath the cap. It's often made from plastic-coated paper, but moving the bottles around inevitably gets acid in the crack between the cap and the bottle and it seeps into the edge of that paper disk, turning it to carbon particles. The acid then drips down the inside of the container back into the rest of the acid, darkening it.

Adding a few mL per liter of peroxide to the acid and then heating it to peroxide's decomposition temperature will virtually always remove the color.

Herr Haber - 27-3-2017 at 03:36

Quote: Originally posted by highpower48

Last summer I bought a couple 850ml 98% sulfuric acid that came plastic bottles. I haven't needed them till now and noticed when I removed them from the plastic bag and light free box that they have turned very dark, close to black. Guess my question is: Is there any issue with this acid? Pretty sure the plastic bottles are the cause. But can i use the acid as normal 98% sulphric acid?

Storing acid next to high powered speakers do that.

(if you play heavy metal for too long: same thing with kids)

Eyeborg - 6-5-2017 at 09:12

Melgar is probably right that the sulfuric acid was reacting with something in the cap. For some applications, dirty sulfuric acid is fine, but if you want to purify it, you can distill it.