Contrabasso
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S.G. Balls
Long ago I had a small lead acid battery that showed it's state of charge by assorted balls floating or sinking. Are those balls available in small
quantities and in chosen SG values? What might they be called?
I want to mess (work) with some strong acid but though the strength is important I shall not need enough to float a hydrometer, so a float/sink ball
would be great.
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watson.fawkes
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The easiest way to get a selection them is to buy a cheap lead-acid battery tester and take it apart. In the US, they're $3 at Autozone, perhaps
cheaper elsewhere.
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hissingnoise
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Do hydrometers *have* to be as long as they are, anyway!
Mine (just checked) is ~27cm.
Why can't they be like, say, 10cm, instead; I'm sure I'd read small numerals easily enough.
27cm. takes a lot of acid to float.
If anyone *does* find SG balls that'd work over a wide range of densities, please let us know?
Now that you mention them, Contrabasso, I seem to remember seeing them yonks ago.
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Mr. Wizard
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The hydrometers are long so the markings on the side will stick up above the liquid and facilitate accurate readings. Imagine an instrument that was
very short like a golf ball and had markings scribed on the side. It would be very difficult to read. Long narrow tubes are harder to make and easier
to break, why would they go through all the trouble?
As to the amount of liquid needed to float the thing, just use a tube just wide enough to fit the hydrometer, not a washing bucket or a beaker. If the
tube is the right size you only will need enough clearance to prevent a bind when it floats. You could actually float a hydrometer in a few cc of
liquid if you had the right size tube.
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gsd
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| Quote: | Originally posted by hissingnoise
Do hydrometers *have* to be as long as they are, anyway!
Mine (just checked) is ~27cm.
Why can't they be like, say, 10cm, instead; I'm sure I'd read small numerals easily enough.
27cm. takes a lot of acid to float.
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Here in India we do get batteries - specifically those for stationary applications like inverters etc. - fitted with very small hydrometers - about
3-4 cm long - on each of the liquid cap. So that the S.G. can be checked even without touching the battery.
gsd
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hissingnoise
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| Quote: | Originally posted by Mr. Wizard.
You could actually float a hydrometer in a few cc of liquid if you had the right size tube. |
A glass tube the hydrometer can move up and down in as a syringe---small inlet for acid at bottom and a rubber bulb at top should make things easier.
For HNO3 the bulb might need to be deformable plastic.
Thanks Mr. Wizard.
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hissingnoise
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| Quote: | Originally posted by gsd
- fitted with very small hydrometers about 3-4 cm long.
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They sound ideal, but they probably won't go above 1.34.
'Pity. . .
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Mr. Wizard
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Another idea goes a step backwards in time and convenience is to weigh out a known volume of liquid and calculate it's density, or use a 1 cc volume
and read the density directly in grams. It's not very convenient, but we all have more time than money, right?
You could use a one ml syringe that you have already zeroed out on a cheap digital scale. You would have to take into account the amount remaining in
the syringe to make sure your test volume was exactly 1 ml. Larger volumes might lead to better accuracy.
I was thinking about buying a hydrometer for making beer, funny how things pop up.
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