Using refractometry to measure liquid concentrations

I always knew light was a valuable resource, especially as a Chicagoan, living through the long gray winters. But I didn’t realize it had so much power in the measurement world till I started learning about process refractometry.

As they meet an object, rays of light can do one of three things: They can be absorbed (like sunlight into your black t-shirt), they can be reflected (like a mirror), or they can pass through and bend (like a rainbow).

That’s refractometry at work. It’s the measurement of the bending of light. The amount the light bends (or refracts) is called the refractive index (RI), the ratio of the velocity of light in the air to the velocity of light in the medium being measured. And the cool part is that when light rays bend, they do it at a predictable angle depending on the concentration of what they’re passing through, so you can use it to test purity of a concentration, or to identify a concentration of particles within a liquid.

For example: Take two glasses of iced tea. Put a spoon in each. Leave one glass unsweetened. Now, add a packet of sugar, Sweet n’ Low, or Splenda into the other. You’ll see that both spoons appear to be bending a little in the glass. And you’ll also see that the one with the packet of sweet stuff in it appears to be bending a bit more. Obviously, the spoon isn’t bending, but the light passing through the tea is moving slower than the light in the air causing the appearance of a bent spoon.

Our customers use refractometers to measure the percentage of a concentration of stuff (some solid) in a liquid.

Refractometers are commonly used in the production of solutions where a consistent concentration is critical.

In the food industry, for example, a process refractometer might be used to measure the amount of “flavor powder” or sweetener in the process batch of lemonade. And in the wine industry, it’s used to measure the concentration of sugar in a liquid, called Brix.

By using a known refractive index, you can measure the purity of a liquid compound. The closer the refractive index is to standard RI values, the purer the sample.

Digital refractometry can provide accurate results, with no calibration drift, and is maintenance free. It provides true measurement of dissolved components without influence by particles or bubbles.  And, as the measurement is done in the process line in real time, it provides a more consistent concentration level than grab-sampling, with an improved production run.

RAECO’s manufacturer partner, K-Patents, has focused its business on various in-line liquid measurements such as concentration and liquid density measurements.  They have 30 years’ experience in providing digital process refractometers for process customers worldwide. They have more than 10,000 instillations on six different continents.

Learn more about K-Patents process refractometry instruments.

Oh, and if you’re the sort that wants to know the exact ratio of pink stuff to iced tea in your glass, you could use a refractometer to help you find out. (Just beware the strange looks you’ll get from your server at Applebee’s.)

Now, it’s your turn:

What’s the best way you’ve found to measure liquid concentration in your production lines?

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