Diluting Conc. Sulphuric Acid

Discussion in 'Top Tips' started by Tom H, Sep 15, 2017.

  1. My previous Sr tech used to take about 2 hours diluting Conc Sulphuric acid, by adding the acid to water at a very slow rate whilst stirring and standing the beaker in a cold water bath.
    Simple and fast and safe method:
    Crush enough ice to fill a 2 litre beaker to three quarters full.
    Measure out specified amount of acid in a measuring cylinder.
    Pour acid over ice, then leave to melt.
    Fill your storage container (in my case a 10 litre aspirator) up to 7 litres with water.
    Add contents of beaker through a funnel.
  2. I've also used this method for years. I also use a large Pyrex beaker and a magnetic stirrer.:);)
  3. We keep a supply of frozen distilled water in ice cube bags for making this and sodium hydroxide solutions. We tried using 2 litre plastic milk bottles as cleappss suggested but struggled to crush it enough to pour it out of the bottle
  4. Dod


    Go to techy dept and borrow a mallet, biggest one they have (possibly even forget to return it) and put ice on concrete floor and take your frustration out on it, very therapeutic it is.
    Tom H likes this.
  5. I have a rubber mallet for such occasions, came with the trolly and I have to say it is always fun to smash things up. But does ruin the milk bottles. I think I might be having a bit too much fun smashing the ice.
    Tom H likes this.
  6. I use 2litre lemonade bottles 2/3 full. Ihave a lovely wedge shaped chunk of Granite. About 2KG. Smooth edges. Very satisfying in a neolithic sort of way.
    Jenny D likes this.
  7. I fill a balloon with water, put it in the freezer. Have a smashing time on the floor (with ice balloon in a thick towel) using a lump hammer.
  8. even with the use of ice, how long does it take for the temperature to go down to room temperature?

    With 2M, it takes a couple of hours before it's ready
  9. o_OHi Tom. I assure you the temperature goes down very quickly with small ice cubes - much quicker than with large cubes.:);)
  10. Hello
    I am around for a while now but actually never posted something. So why not start here ;)

    Its a bit surprising how much effort you ppl put into making dil. sulphuric acid. Normal target concentrations like 2M, 1M or 0.5M (1N) can be done without any additional cooling in a reasonable time.
    Some guy did this nice calculation and graph ( http://www.chemical-supermarket.com/files/Acids/Exothermic Dilution of Sulfuric Acid.xls ) which shows what temperature increase you can expect upon diluting 98% H2SO4, which roughly conforms with my experience.

    For example making 1L ~1M from 98%: Fill 800ml of dest. water in a 1000ml volumetric, slowly but steadily add 56ml of H2SO4 98% (stirring is helpful but not necessary). Wait until the solution has cooled, or use additional cooling. Fill up to 1000ml with water.

    The target concentration is roughly 7% which increases the temperature by about 15°C as seen in the graph, which easily cools back to room temp. in 30-45 mins (lunch break :)) or overnight. Other tricks like ice, fridge, cold water to make the solution are usually not needed. And it definitely doesn't take 2h, unless thats the point ;) ... Making 2M the same way, increases by 30°C. Also okay, but takes longer to cool.

    Of course, if you want to make stronger concentrations things get different, as the solution should never come close to boiling point. Basically making anything above 2M or 15% from 98% have to be done with additional cooling and/or very slow adding, described by previous posters.

    So long :D
    Heidi Ross and clairelucas like this.
  11. If you put the 2 L bottles in hot water first until you hear the ice crack throughout inside then you will have more luck getting it small enough to pour out. Use a hammer on the floor and then bash it with the claw of the hammer to cut round the bottle or use scissors... I won a jumper in the 90s for this technician tip and it still works, for me anyway..
  12. Completely off topic but do you still have the jumper? Is it very 90s? Lol
  13. Can't think what happened to it, but large sweater multicoloured, (I guess 90s) M&S gift voucher from CLEAPSS....

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