Summary for percent by volume to oz/gal Discussion
percent by volume to oz/gal is the thread’s core conversion question, and the answers stress that the math depends on what form the chemical is in. Xp ee asked how to convert v/v to w/v when specific gravity is known; the reply explained that you can use unit conversions from volume fraction to mass per volume, but only if you know whether the material is a pure substance or a stock solution with its own composition. For the simpler liquid-to-liquid case, McHenry, Illinois and Guillermo Marrufo both noted that a U.S. gallon contains 128 fluid ounces, so 25% by volume equals 32 oz/gal and 20% equals 25.6 oz/gal. Tom Gallant gave the same shortcut using multiplication by the decimal fraction. In the later NaOH question, Chris Owen said a 5% by volume solution of a 100 oz/gal NaOH stock would contain 5 oz/gal of NaOH, while Ray Kremer asked for the actual form of the NaOH before a precise conversion can be made.
Q. Please how do you convert from v/v to w/v if specific gravity is given?
Xp ee
Student – Nigeria
August 4, 2023
A. Xp ee,
This would be easier to demonstrate if you’d given an example of the calculation you need to make. However, I learned a long time ago in science class that you can get pretty far just by taking the numbers you have and seeing what unit conversions you can make, heading in the direction of the units you want to end up with.
In your case, you start with v/v, let’s say liter/liter, probably liters of some specific component X per liters of total solution. You have (presumably) the specific gravity of X, which is a fancy term for unitless density, though it so happens that because the metric density of water is 1, you can add on metric units with no change to the number. So you have the density of X in kilograms/liter.
In which case, you can multiply your v/v concentration by the density, giving you:
(L X / total L) * (kg X / L X) = kg X / total L
But wait! Was X a pure substance, or was it a stock concentrated solution? Maybe your solution X was 75 wt% of Y and 25 wt% water, and the w/v you want is kg Y / total L, not kg X / total L. In which case:
(L X / total L) * (kg X / L X) * 0.75 (kg Y / kg X) = kg Y / total L
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
August 10, 2023
⇩ Similar, related, Q&As — oldest first ⇩
Q. We are in the process of revising all of our internal titration procedures and we came up with a question that we cannot seem to come up with a solution for — we hope you have an easy answer for us. Per our Spec. it calls out for 20-25 % by volume of HN03 and a concentration of 27-33 oz/gal. What is the conversion factor we should use after titration to convert the percent by volume to oz/gal. in this case? Your input would be very appreciated.
Thank You,
Steven Rij
Plating Shop – Salt Lake, Utah, USA
2004
 | A. Based on your question I suspect you may find it very hard to understand and work with titrations and other lab procedures. You should know by now, but one US gallon has 128 fluid ounces. So, a concentration of 25% (1/4) by volume means 128/4 = 32 ounces per gal., whereas 20% (1/5) means 128/5 = 25.6 oz/gal. This is for two liquid substances mixing together. If one of them is solid, then the ounce represents mass not volume and the ratio is different. Guillermo Marrufo A. One gallon contains 128 Oz. 25% is 1/4. So you want 1/4 of the gallon to be HNO3. Divide 128 by 4 to give an answer of 32 Ozs. 20% is 1/5, but dividing 128 by 5 is the hard way. Instead, multiply 128 by 0.2, which gives 25.6 Ozs. The first example could have also been done by multiplying 128 by 0.25. Just a matter of which method is easier. Tom Gallant |
Q. Converting percent by volume to oz/gal NaOH.
We have just added a new cleaning tank and I need a conversion formula as the titration I am using is stated in oz/gal.
Our tank is 20 gallons at 5%.
Thank you for your help.
Connie Rancourt
– Brattleboro, Vermont, USA
December 4, 2012
| | A. NaOH is a solid and not a liquid, so I see no way it can be made up by volume. You probably use 50% caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] solution, which contains 6.25 pounds or 100 oz/gallon of NaOH. A 5% by volume solution of this would contain 5 oz/gal of NaOH. Chris Owen A. Connie, in what form is the NaOH? Solid, 50% in water, or what?
|
Q. I am trying to compare out shop process control limits, which we list in weight percent, with limits in the Metal Finishing Guidebook which list the concentration for acid pickling and etch solutions in terms of percent by volume (v/v). I am struggling to understand how the percent by volume for acids is calculated. Is it assumed that you begin with some standard stock concentration for each acid?
Brooke Nahring
– Bremerton Washington
July 30, 2021
A. Brooke,
That is generally the case, although also generally the recipe or standard will describe the stock solutions in terms of weight percent or specific gravity or some such.
Some acids in their “pure” form are anhydrous powders, while others are essentially never available outside of aqueous solution.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois