Safely storing sulfuric acid

  1. Can a solution of 35% sulfuric acid and 65% water be safely stored in a plastic bottle? That is, does sulfuric acid of this concentration react with any or all plastics? if plastic is not acceptable, what type of storing container could safely contain the acid?

    If interested, what I have in mind here is removing the electrolyte from a fully-charged lead-acid battery to be reinserted into the cells of the battery at some future time to reactivate the battery. The purpose is to be able to have an arrangement for providing emergency 12V power with minimal maintenance, that is, avoiding the need to periodically charge the battery.

    An additional concern of mine is whether or not the sulfuric acid in an uncontaminated storage container would decompose over time. If decomposition would occur, at what rate would it occur?

    Searching with google, I couldn't find any information concerning this, except that it is apparently easier to store sulfuric acid in a highly concentrated form.

    Thanks in advance for any information about how to go about doing this in a safe manner.
     
  2. jcsd
  3. ShawnD

    ShawnD 986
    Science Advisor

    Yes sulfuric acid can react with plastic. Esters in particular are easily destroyed by acid. Use glass, or a container that was specifically designed to hold acid.

    I have no data to back this up, but this sounds like a bad idea. It's possible that some things in the battery need to be kept wet in order to work properly, and that the battery won't work immediately after you pour the acid back into it. As an example, if the sides of the battery are separted by a membrane, it might take time before the membrane is wet enough to be usable. Or if the battery has something like a tube filled with cotton balls connecting the two sides together, that entire tube has to be set before ions can flow from one side to the other.

    If you really want to keep the battery usable for a long period of time, put it on wood blocks. Car batteries tend to die very quickly if you let them sit on concrete, but they hold a charge for months/years if they sit on wood blocks.

    The acid by itself should not decompose at any noticeable rate, but it's possible it would react with stuff left in the container. Sulfuric acid stored in a glass bottle should keep a very steady concentration over long periods of time.
     
  4. chemisttree

    chemisttree 3,721
    Science Advisor
    Homework Helper
    Gold Member

    The case of the battery in question is made of ... plastic.
     
  5. reply to 12-01 post by ShawnD

    Thanks for your feedback, especially the information about lead-acid batteries holding their charges well over months to a year.

    At the website www.batteryfaq.org, there is an article going into lead-acid batteries retaining charge in great detail. Apparently storing the battery at cold temperatures (below freezing) is useful for slowing down the rate of discharge while the battery is not used. Conversely, warm temperatures severely curtail the length of time a battery can be stored without significantly losing its charge.

    At the same site, they say that the need for supporting a battery above a concrete floor on wood to prevent discharge does not apply to contemporary lead-acid batteries constructed with plastic cases.

    Regards,
    Pete
     
  6. ShawnD

    ShawnD 986
    Science Advisor

    Interesting info you've found. Thanks for the link.
     
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