sulpheoric acid for batteries

hi all

plz tell me what concentration of sulpheoric acid is used for automotive batteries i.e.
whats the ratio of water and acid

i think usually a pure acid H2SO4 is 98% concentrated so how much it should b diluted to use in battery

Battery acid is around 35% H2SO4 to 65% distilled water - by weight, but is normally given a specific gravity, as it's easier to measure - should be 1.265 at 27 Celcius.

Get a hydrometer from a garage, mix the acid and water, then fine-tune it with the hydrometer to 1.265 s.g.

Remember: adding acid makes the s.g. higher (it's denser than water) and, most importantly,

Add the acid, slowly, to the water, NOT water into acid! Mixing the two gives off a lot of heat, and adding water into concentrated (98%) acid can flash-boil the first few drops, spraying acid all over. Not nice. Sorry if you're a chemist and already know this.

FoxyRick.

some people told me

acid is in 2 types
comercial
grade A

which one is used i dont know

Hmmm, I don't use those descriptions, but I imagine they are what I would call 'Technical Grade' (commercial) and Standard Laboratory Reagent, or SLR (Grade A).

'Technical grade' means that the acid has not been particularly purified or tested for purity. It would probably be good for a battery, but I doubt there is much difference in cost, at least for small quantities.

SLR is tested (and the results given) and has few enough impurities that they don't make any difference in most laboratory reactions.

If you want really pure stuff, for analytical work, there is 'Analytical Grade' which has more accurate testing, it is not always more pure. There is also a version purified (or at least tested) for use in the food industry (lead and other heavy metals often associated with the acid are lower concentrations). I have used some that cost around £200 per litre for trace element mass spectrometry, but that was special order stuff. Amazing being able to measure in picograms per litre though!

In short, garages probably use Technical Grade, and I bet their distilled water isn't all that pure anyway, so that is probably fine.

Small impurities can make a difference though, so if the SLR grade is only a little dearer, I would use that.

Just one other thing, if anyone offers you 'fuming sulphuric acid', don't use it. It contains free SO3 and is far too nasty!

Cheers,
FoxyRick.

ok it is good but one thing more about ratio of water

i think that i will get comercial acid and would i mix it up with water with ratio 3:1
the ratio i m not confident to use

If you want to measure by volume rather than weight, the ratio is:

30.1 cm³ acid : 100 cm³ distilled water

at 20°C, based on concentrated acid being 1.84 s.g.

FoxyRick.[/b]