Converting baumé to Concentration

Howard,
Basically it's the same reason a handful of (very significant) countries are still using customary/imperial/inch-pound units instead of the metric system: inertia. If something works "well enough", and the alternative is superior but not drastically so, especially if the transition inherently must be quick or otherwise difficult (either from a technical perspective or merely a "relearning" aspect), it often does take a government decree to get people (and/or industry) to switch away from what they've been using "forever".

I rather note that degrees Baumé especially, is not used by any serious modern chemist, but seems to be mostly found in industrial commodity chemical sales. You're never going to get the chemical industry to change the concentration of the acids they sell, because then everybody would have to adjust their recipes. The fact that these concentrations were originally defined via an archaic unit system is for all practical purposes a historical footnote, but just like it's easier to say you're buying "a gallon" of milk than "a 3.79 liter bottle" of milk, it's easier to say that nitric acid is sold at "42° Baumé" than "67.18%". Though at this point, the bottle of milk does typically mention "3.79 L" on it, and nitric acid documents do typically mention "67.18%".

A. Someone will probably do your work for you, but you need to find it for yourself.
• Lange's Handbook of Chemistry [adv: on Amazon, AbeBooks, or eBay affil links] ,
• The CRC Handbook of Chemistry & Physics [adv: on Amazon & AbeBooks & eBay affil links] ,
• Perry's Chemical Engineers Handbook [adv: suggestions on Amazon, AbeBooks, or eBay affil links]
and a few others all have conversion charts. The next problem is 5% of what? Many would equate this to 5% by volume of reagent quality HCl, which is 37% by weight hydrogen chloride in water. Also is it 5% by volume (of what) or 5% by weight (of what)? If this is for a chemical analysis, there will be a listing (in the front or the back of your analysis source book) of the strength and or purity of each chemical.

A. That was a very good and educative reply by James Watt; but it seems (and I'm probably wrong) that only HCl's strength is measured in Baumé scale?

A. Actually, the concentration of a lot of acids (HNO3, H2SO4, HCl, etc.) are measured in degrees Baumé (heaviness scale).

A. Nitric acid is also sold by baumé. Sulfuric is frequently sold by % or by specific gravity, but I bet someone sells it by baumé. Reagent grade HCl (muriatic) is sold by %.

A. Hi. Just to complete this sub-thread before moving on, Baumé is an old scale invented by Antoine Baumé whereby the strength of acids is expressed by their relative weight. According to Wikipedia , the relationship between specific gravity and baumé at 60 °F is:

S.G. = 145 / (145 - °baumé)

Some references use 144 rather than 145. But in any case, since the only unit in the formula is specific gravity, the units for baumé are the same as for specific gravity, which is to say it's a pure number not dependent upon metric system vs. inch-pound system.

Regards,

A. Hi. That doesn't sound right to me, Doc. But I think it's far easier to think in terms of the amount of acid rather than the amount of water ...

You apparently want 100 ml of solution for your addition or analysis, and you want it to contain 10% (by volume) of "pure" HCl. So you want your 100 ml of solution to contain 10 ml of HCl because 100 x 10% = 10 ml.

If the starting solution is 32% (by volume) HCl, each ml of that solution obviously contains .32 ml of "pure" HCl. To obtain 10 ml of "pure" HCl, you would require 10/.32 = 31.25 ml of your 32% solution -- which you would add to 68.75 ml (100 ml total - 31.25 ml) of pure water to reach your 100 ml of 10% strength.

Regards,

A. Typical "commercial grade" HCl is 32-33%. In my experience, when plating facilities talk about xx% concentration in an acid bath, they mean xx% of the commercial grade acid. For example, a "25% muriatic bath" is 1 part of 32-33% HCl and 3 parts water.

A. Hi Denise. We appended your inquiry to a thread which explains some rationale for using 32-33% commercial strength HCl as the basis for your calculations, and which implies that expressing concentration by volume rather than weight offers practical advantages.

As additional justification, I would add that HCl is not a liquid, but a gas dissolved in water, so higher concentrations than that aren't practical anyway and would take us into rather "artificial" calculations. I'd say the answer is to adopt the convention that Matt says is the most common one (concentration by volume, measured against the 32-33% commercial standard). But I'm not a chemist :-)

Regards,

A. Chemists tend to like concentration in terms of moles per liter, or at least some mass per volume that can be converted to moles per liter. Most useful things that chemists tend to think about only operate in units like this. We always keep in mind that a concentrate solution is already some quantity of material in water.

Manufacturers tend to like concentration in terms of volume percent, volume ratio, mass percent, or some other simple measurement that can be used by workers who possibly have forgotten everything they learned in the one semester of chemistry they ever had in their life. Concentrate solutions are viewed as mystery stuff to be mixed in some set quantity with another set quantity of water.

So yes, a chemist in the manufacturing field must be ready to use whatever conversion factors are available to move back and forth between units that are useful for chemical calculations and units that are useful on the factory floor. The major thing is to know your audience, and to know what audience a set of mixing instructions was meant for.

A. Hi Ryan, For a 25% v/v nitric acid solution you will need 130/4 = 32.5 litres of acid. When you say 2-3% m/v dichromate then that is the equivalent to 20-30 grammes per litre.
So 1 US gallon = 3.78 litres, Then 130 x 3.78 = 491 litres of liquid volume.
491 x 30 g/l = 14730 g or 14.7 kg of dichromate.
Hope this helps and good luck.

A. You would find life much simpler if you were to work in grammes per litre.
You avoid problems like an imperial gallon being 4.2 litres and an American gallon 3.8 L
Ounces - Is that Avoirdupois or Troy as used for gold and silver? Or could it be the apothecary or perhaps the fluid ounce?
Did you know that there are two baumé scales? Light baumé is for solvents and heavy baumé for aqueous solutions. The problem is that both hydrometers look similar. Pick up the wrong one and----!

I wonder how many mistakes these archaic units cause each year.

Hi Geoff. As an American engineer I appreciate the dichotomy there! We've always like sticking with our own system because if we can make others struggle with what we're used to, instead of us struggling with what they are used to, it gives us a leg up :-)

On the other hand, I can't tell you how many times in my career I've seen construction errors because of switching back and forth between inches and feet & inches. A foot is 12 inches, but is accidentally converted to 10 inches constantly --

"6 foot 2, eyes of blue, coochy coochy coochy coo ..."

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Okay. This is not overly complex math, but it's been a long time since math class for some of us. I'll stick with Imperial units to keep it simple, there's nothing here that is particularly made easier by converting to metric.

130 * .20 = 26
130 * .25 = 32.5

So you need your 130 gallons of bath to include between 26 and 32.5 gallons of concentrated nitric acid.

130 gallons of 20-25% nitric acid will weigh a little more than 130 gallons of water does. We can decide to ignore that and just go with the density of water 8.35 lb/gal, in which case

8.35 * 130 = 1085.5
1085.5 * 3 / 97 = 33.6
1085.5 * 2 / 98 = 22.2

Add between 22.2 and 33.6 lbs of sodium dichromate. Or weigh out a known quantity of the 20-25% nitric solution to get the correct density and run the math using that.

As an aside, if you ever want to get away from using such nasty chemicals, see if you would be allowed to use the "Method 2" passivation in 2700.

A. Hi Haider. The number "140" does not appear on this page ... maybe you mean 145? Antoine Baumé invented his scale, which is:
Specific Gravity = 145 / (145 - °baumé).
The number 145 was perhaps arbitrary, but once he chose it we must honor it as the conversion between specific gravity and the baumé scale

The number "130" in Ray's answer was just in response to Ryan Thompson's 130 gallon tank.

Luck & Regards,

A. Hello Aijazulla,
If I understand your question correctly, you probably know sulfuric acid is supplied in various concentrations. battery acid ⇦ this on eBay or Amazon [affil links] is around 35%; 50% and 98% used in the plating industry, as well as other industries. Purity is also an important factor when using sulfuric. This is why there are different grades of acid available, i.e. - PC, electronic, and reagent grades are some examples. Also sulfuric acid absorbs water from the air, especially at high concentrations. A simple lab titration to determine concentration is the norm for proper analysis. Determination by volume alone would not be accurate. Hope this answers your question.

A. There may be a simpler way, but this is how I do it.

First, on the internet or a chemical handbook, find the specific gravity (SG) of a 15%, by weight, sulfuric acid solution. This will vary depending on the temperature. Many of the charts are based on 20 °C and, since that is close to room temperature (68 °F), that is what I would use. I know of no formula that will directly give the relationship between the concentration by weight and the specific gravity. The easiest way is to find and use a chart.

According to one chart I found, the SG of 15%(w/w) sulfuric acid at 20 °C is 1.102g/cc. Therefore, one liter would weigh 1.102 X 1000 = 1102g.

At 15%, there would be 1102 X .15 = 165.3 grams of sulfuric in one liter.

One mole of sulfuric weighs about 98 g. Therefore, there is 165.3/98 = 1.6867 moles of sulfuric in one liter of 15%.

Assuming the concentrated sulfuric you are using is 96%, a liter contains 18 moles. Therefore, to make up a 15%, by weight, solution would require 1.6867/18 = .0937, or 9.37% of 96% sulfuric, by volume.

A. Hi Michael. You don't say what the starting concentration of your HCl is (it's not 100%). Step 1 is to find out the concentration of the acid you're starting with. Step 2 is to study the MSDS sheet and be sure you are properly trained, and have the right PPE (personal protective equipment) to do the job safely. Then step 3 can be to prepare the diluted solution per the calculation shown above in my response of December 2012 to Dr. W.A.C. of Pakistan.

That is:
- If you want 1000 gallons of 5% HCl, you'll want the 1000 gallons to contain 50 gallons of "pure" HCl (5% of 1000 gallons).
- If you start with 32% HCl, each gallon will contain .32 gallons of "pure" HCl, so to get 50 gallons you'll need to add 50/.32 = 156.25 gallons of 32% HCl.
- Since you want to end up with 1000 gallons of solution, and you'll be adding 156.25 gallons of the 32% HCl, you need to start with 1000-156.25 = 843.75 gallons of water.

"Do as you oughta, add acid to water". Best of luck.

Regards,

A. Ted .. you are giving a good help to this site.
Regarding the chemical formula for dilution of any concentrated solution :
Concentration * Volume (of conc. solution ) = Concentration * volume (of final dilute solution )
(concentration could be expressed in % or moles or normality )
As a rule of dilution, Concentrated solution should be added to the dilute or to water in order to absorb the heat of dilution.
Regards,

A. Reading through this whole very informative thread (plenty of good humour about the US vs Metric measurements too; I've got a copy of Josh Bazell's 'How To Use The Metric System' taped to my lab door as a warning and have shooed people out with the instructions to read it, come back in, and talk to me in metric)...
I have one very simple thing to add to the conversation. If you've got chemicals, you've got Safety Data Sheets (aka MSDS) too. If you don't, hurry up and get them! Anything you buy in baumé will be listed in %w/v somewhere in there, and you can use that as a starting number for dilution calculations.

Great tip, Rachel. Thanks!

I couldn't find your ref with google, but did find
http://rebrn.com/re/metric-system-vs-imperial-system-92644/
which seemed to at least allude to his book "Wild Thing" and its metromedy. My favorite line in the comments was "Jet fuel can't boil American water" -- which was probably only funny to me and whoever wrote it.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Ed. note Sept. 2023: Don't go to that website! That's a problem with links: bad actors buy up expired links :-(

"Wild Thing"

on AbeBooks

or eBay on

Amazon

(affil links)

Indeed from 'Wild Thing'. Here it is:

HOW TO USE THE METRIC SYSTEM
"In metric, one milliliter of water occupies one cubic centimeter, weighs one gram, and requires one calorie of energy to heat up by one degree Celsius, which is one percent of the difference between its freezing point and its boiling point. An amount of hydrogen weighing the same amount has exactly one mole of atoms in it. Whereas in the American system, the answer to How much energy does it take to boil a room-temperature gallon of water? is Go f*** yourself, because you can't directly relate any of those quantities."
-Josh Bazell

Rachel Mackintosh
lab rat - Greenfield, Vermont

A. Hi Chikaiko. Alkalinity & acidity are not the same thing as pH, so your theory that you can determine the required amount of NaOH from a pH reading may be flawed from the start. But you never do a neutralization like this by theory anyway. You always do a beaker test / lab titration and then scale things up, so why drive yourself crazy with conversions from the defective broken baumé scale? Instead, do a lab neutralization, measuring the quantity of "11 Baumé" required, and proportion things upward. Good luck.

Regards,