How to Mix Chemical Solutions to a Certain Purity or Percent

Changing Concentrations of Chemicals

Introduction

We normally sell concentrated forms of chemicals. Many applications may require diluted solutions of these chemicals and especially when the concentrated chemical is not 100%, it can be difficult in determining how much of the chemical is needed to make the solution needed.

The Make-up of Chemical Solutions

Chemical solutions are normally made by mixing water and the concentrated form of the chemical. Most of the time, when you buy chemicals with impurities, most of the impurity is actually just water. For example, our 98% sulfuric acid contains 2% water plus a few other impurities. A 32% solution of sulfuric acid is 32% sulfuric acid with the remainder mostly as 68% water.

Measuring Chemical Solutions

When most people think of mixing two fluids together, they will do it by volume. Unfortunately, different chemicals have different densities and these densities change based on temperature. It is also hard to measure out the volume of a fluid accurately, especially when dealing with small quantities. The best way to mix chemical solutions is by weights. Weights do not ever change and will directly determine the mass of the chemicals you're dealing with unless you leave the planet Earth.

Safety

If you're dealing with an acid or a base, mixing it with water is likely to be an exothermic reaction. Be sure you mix the chemicals with the water slowly and stir constantly to evenly distribute the heat. If the mixture heats up too rapidly, it could boil the water in the solution.

How to Make the Solutions

The Data Needed

Before you can do anything, you will need to know the density of the concentrated chemical you are using for the solution, the density of the final solution to be made and the purity (in %) of the concentrated chemical used.

Downloadable Excel Sheets

In order to make the calculations easy, we have created the following excel sheets. Please download both before proceeding.
Download Mixing Chemical Solutions Calculation Sheet (xls)
Download Mixing Chemical Solutions Example Sheet (xls)

Instructions

In the Mixing Chemical Solutions Calculation Sheet, enter the density of the chemical used to make the solution. This is found on the chemical's MSDS. Next, enter the density for the solution to be made. This can be found on an MSDS for that solution % (try searching google). On the next line, enter the % purity of the concentrated chemical being used to make the solution. Next, enter the percent purity of the solution to be made. Finally, enter the final volume desired of the solution to be made.

Results

Below the entered data, the results will appear in the results box. Weight of the product to add is how much of the chemical you should add into the solution in Kg.

Weight of water to add is how much water to mix with this chemical. The total weight of the solution to be made will be shown below this. This is the weight of both the chemical and water mixed together.

The sheet also calculates the volume of both the chemical and water to be added incase you do not have a scale readily available or accuracy is not too important. Total volume of the solution is also shown below these two numbers.

All results shown are in the metric system. For those who prefer English units, check to the right of the results for everything in English units.

Frequently Asked Questions

Q: How do I mix solutions with a chemical that is a solid?

A: The calculations are done by weight, so it doesn't matter if it's a solid or a liquid. If a final solution is desired to be a liquid, check the chemical's MSDS for % solubility in water.