Acidic maths

I've acquired a quantity of 77% sulphuric acid. Not enough to melt people,
unfortunately, but loads more than enough to fill the spare battery I have
sitting here. Now, I find that batteries like ~35% acid so would I be right
in thinking that a roughly equal mixture of this acid and water would do the
job or am I talking complete bollocks as usual?

 

No, you're right. You actually want to add a little over an equal
amount of water - 110% to be precise.

 

Never add water to acid. It's one of the two things that make you go blind,
at least according to my teachers many years ago.

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Colin Irvine

And FFS remember "Always do what you oughta - add the acid to the
water".

--
Wicked Uncle Nigel - "He's hopeless, but he's honest"

I have already made the greatest contribution to the fight against climate
change that I can make: I have decided not to breed. Now quit bugging me and
go and talk to the Catholics.

 

Bugger - 120% I think.

 

<g> I used to think of Sulphuric and Water as Sailors and Women.

 

No, you were right with 110%.

1 litre of 77% acid contains 770ml neat acid and 330ml water.
770ml acid to 35% would be 770ml acid and 1430ml water.
1430ml minus the 330ml you've already got would be 1100ml added or 110%
of the 1 litre you started with.

 

Thanks, and to the others for considering my eyesight. I always think of it
as A to W.

 

That's how I got 110%. Then I realised the initial mixture would be
770 to *230* and 1200 added ...

 

Not just any water - distilled water.
Allways add the acid to the water NOT water to acid.
For battery use you should measure the specific gravity using a hydrometer,
the most common values are 1.230 or 1.260 but check the battery specs
because my memory has been known to suffer random bogosity.

 

Sounds about right. Just be sure to add the acid to the water, not the
other way around.

 

Just make sure you add acid to water if you are diluting it. 77% is rather
concentrated and adding water to concentrated Sulphuric can have unfortunate
consequences in terms of spatter. I doubt if 77% is strong enought to cause
a major spatter problem but no need to take any chances.

 

<cough>
OhYesSoItWould

 

I always thought it was the other way round and if not, then toping up
batteries with water must be a pretty dodgy exercise.

--
Beav

VN 750
Zed 1000
OMF# 19

 

Me too, as I posted a minute ago. It's fucking odd how an idea stays planted
innit?


--
Beav

VN 750
Zed 1000
OMF# 19

 

Battery acid is already diluted. It's adding water to concentrated
acid that's supposed to be bad.

 

It's diluted enough in batteries not to matter.
But when diluting concentrated sulphuric acid, that's how you do it.
The acid wants to be hydrated so much it fights itself to grab hold of the
water, so to speak. That's what causes the spitting.

That's why concentrated sulphuric acid burns so badly if contacting flesh,
it acts as a desiccating agent as well as an acid.

 

Damn right. I can still remember the chemistry lesson where the
teacher chucked some sugar into concentrated sulphuric acid. The acid
took all the hydrogen and oxygen out of the sugar (it was in there in
the same 2:1 ratio as water) leaving a great pillar of carbon emerging
from the flask. We were impressed.

 

I remember that one too. I also remember being beaten about the head and
shoulders by my dad after an experiment in the garage with sugar and
saltpeter had a greater yield that I expected.

 

I have the scars of a large 97% sulphuric acid explosion at Dounreay.
It's ability to eat through my protective lab coat and clothing was
impressive and the wounds took over a week to close. TBF the perspex
helmet and synthetic gloves did mostly survive.