# How to make concentated sulfuric acid from battery acid



## catfish

How to produce concentrated sulfuric acid from battery acid.

Use regular battery acid acquired from your local NAPA store. This can be purchased in one (1) quart, 1 ½ gallons, or 5 gallons quantities. This diluted acid is inexpensive.

Assumptions:

Regular battery acid is 65% water (H2O) and 35% sulfuric acid (H2SO4). This computes to 1.25 grams specific gravity per cubic cm or 1 ml. (Often referred to as 1250 specific gravity.) This is only 1.25 x 1000ml, another way of saying it.

Distilled water is 1.0 grams specific gravity per cubic cm or 1 ml.

98.3% pure sulfuric acid weighs 1.84 grams specific gravity per 1ml.

Heat required = mass x specific heat x temperature change. 1 gram of water (H2O) takes 1 calorie to change the temperature 1 degree C.

Water (H2O) boils at 212 F or 100 C.

Sulfuric acid (H2SO4) boils at 640.4 F or 338 C.

To make concentrated sulfuric acid:

Take 100 ml of battery acid and place in a heat resistant container, Pyrex or equivalent and heat on a hot plate or equivalent heat source. Preferably out doors.

Weigh 1 ml of distilled H2O in a 10ml test tube or equivalent container on a small electronic scale in grams with at least + or – 1/10th gram accuracy. This should weigh 1.0 grams. Remember to zero your meter with empty test tube on it in-order to get an accurate specific gravity weight.

Weigh 1 ml of the battery acid H2SO4 using the same procedure and you should come up with 1.20 to 1.25 SG per 1 ml. This can vary somewhat due to the charged state of the electrolyte (battery acid) no problem, this is just a relative reading.

Place hot plate in a metal container in case you have breakage or mishap. I use a metal foot tub. This also blocks the wind from the hot plate and allows it to be more efficient in heating.

Place a good grade glass thermometer in the solution and monitor.

Place on high heat and watch temperature until the solution reaches ~230 F or 110 C.

The solutions will be at a low boil and you will be able to see the boiling action and also observe the steam rising off it.

Maintain the temperature at 230 F until all boiling action stops. The steam will stop rising too. Note: the amount of time for the solution to boil off all the water will be determined by the mass of your solutions. 100ml takes about 40 to 45 minutes. This may vary due to several factors, such as ambient temperature and quantity or volume of your solution.

Let the solution cool to room temperature and take 1 ml of it and weigh it like you did the battery acid. Take the remaining solution and measure the volume that is left. It should be ~ 35 ml this time you should have a specific gravity of ~1.80 per ml. if you have boiled all the water off the solution.

The remaining acid should be 90% plus if you measure 1.80 or above. Remember that pure H2SO4 (98.3% concentration) weighs 1.84 grams per ml. Just do the math and 1.84 -1.0 =.84 /.855 (theoretical 100% Concentration) = 98.3% Realistic concentration. Divide 1.855 into your last specific gravity weight and this product will be the percentage of concentration of your finished product. Example 1.80 -1.0 =.80/.855 = 93.6%. This should meet any requirements you may encounter in the gold recovery/refining business.

This sulfuric acid is very pure and has no additives or inhibitors. It is great for the electrolytic cell and many other uses such as making nitric acid.

Be careful. Hot acid burns.

If you have any questions send me an email or post.

Catfish


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## goldsilverpro

Bravo!


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## Noxx

Good job CatFish, it will be verrrrry useful.


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