You have probably noticed that some liquid concentrations are marked as a percentage while others are noted as a normality. They can, in theory, be identical concentrations at times. But more often than not, they serve very different purposes in a laboratory.

Normality is a measure of concentration equal to the gram equivalent weight per liter of solution. It is directly related to molarity and depends solely on the valence of the molecule. Molarity is a simple expression of formula weight per volume of liquid. When the valence of a molecule equals 1, the molarity equals the normality. In certain molecules, for instance Sulfuric Acid, the valence is 2. Therefore, Sulfuric Acid 1N is equal to Sulfuric Acid 0.5M. For example, Sodium Chloride has a formula weight of 58.44g. A 1M solution of Sodium Chloride is therefore made of 58.44g per liter of solution, and since the valence value is 1, Sodium Chloride 1N will also contain 58.44g of salt per liter of solution.

Normality solutions are produced to meet strict tolerance standards. Many manufacturers in the industry market their normality solutions with a tolerance of ±0.5%. This means that if you purchase a solution marked as 1N from one of these manufacturers, the solution you receive is guaranteed to be between 0.995N and 1.005N. Here at Exaxol, we maintain even tighter tolerances of ±0.2%. This means that if you buy a solution at 1N, you are guaranteed to receive a solution between 0.998N and 1.002N.

These tight tolerances are critical in detail-oriented lab practices such as titrations. If you want to test the exact purity of an in-house solution, using an Exaxol normality solution as a titrant will guarantee the accuracy of your test results to within ±0.2%. This allows you to properly gauge the amount of your solution needed in a precision reaction.

The main difference to a percent solution is the extent of tolerance. Percent solutions can be manufactured by weight/weight, weight/volume, or volume/volume. The industry standard tolerance for a percent solution is ±5.0%, which is 25 times wider than Exaxol’s ±0.2% tolerance for normality solutions. Because of the wider tolerance, these solutions are much less expensive, and are best suited for less precise purposes.

In summary, if you are looking for precision accuracy with your solutions, be sure you are working with normality standards. If you are doing less precise reaction chemistry, you may find that the lower price tag of a percent solution better suited for your needs. Either way, Exaxol has your needs covered!