The HI96831 Digital Refractometer utilizes the measurement of refractive index to determine the percent volume and freezing points of ethylene glycol based solutions. Ethylene glycol is used in glycol cooling systems for industrial applications. Maintaining the appropriate percent of glycol is important in glycol chillers as too low of a percentage could lead to the system freezing and rupturing while too much glycol will reduce the systems efficiency. The instrument converts the refractive index of a sample to percent volume or freezing point. These conversions are based on internationally recognized references for unit conversion and temperature compensation for glycol solutions (e.g. CRC Handbook of Chemistry and Physics, 87th Edition). The HI96831 is an easy-to-use tool for measuring freezing point and percent volume in ethylene glycol solutions, in the field or in the lab.
- Designed for ethylene glycol analysis
- Automatic Temperature Compensation
- 0 – 100% Volume range with ±0.2% accuracy
- 0 to -50 °C freezing point range with ±0.5 °C accuracy
Making a Standard Solution
To make an Ethylene Glycol Solution, follow the procedure below:
- Place container (such as a glass vial or dropper bottle that has a cover) on an analytical balance.
- Tare the balance.
- Volumetrically add X mL of high purity ethylene glycol (CAS #: 107-21-1; MW 62.068) to a 100 mL Grade A volumetric flask.
- Use distilled or deionized water to bring the flask close to the total volume, mix, allow the solution to return to room temperature.
- Once the solution has returned to room temperature use distilled or deionized water to bring the total volume to 100 mL. Mix solution well before use.
| Ethylene Glycol | Total Volume | Expected Freezing Point Value | |
| 10 % V/V | 10.00 mL | 100.00 mL | -3.8 °C (25.2 °F) |
| 40 % V/V | 40.00 mL | 100.00 mL | -26.3 °C (-15.4 °F) |
Measurement Units
Freezing point is displayed as a temperature from 0.0 to -50.0 °C corresponding to 0-58 % by volume. The display blinks the freezing point when the concentration of Ethylene glycol is greater than 78 % concentration by volume. When the display shows “LO”, the freezing point is at a minimum (below -50 °C).
Refractive Index
The HI96831 takes measurements based on a sample’s refractive index. Refractive index is a measurement of how light behaves as it passes through the sample. Depending on the sample’s composition, light will refract and reflect differently. By measuring this activity with a linear image sensor, the sample’s refractive index can be assessed and used to determine its physical properties such as concentration and density. In addition to the linear image sensor, the HI96831 uses an LED light, prism and lens to make measurement possible.
Variations in temperature will affect the accuracy of refractometry readings, so the use of temperature compensation is highly recommended for reliable results. The HI96831 contains a built-in temperature sensor and is programmed with temperature compensation algorithms in accordance with internationally recognized references which vary based on the parameter being measured.
| Specification Name | Detail |
|---|---|
| SKU | HI96831 |
| Ethylene Glycol Range | 0 to 100% |
| Ethylene Glycol Resolution | 0.001 |
| Ethylene Glycol Accuracy | ±0.2 % |
| Freezing Point (FP) Range | 0 to -50°C (32 to -58°F) |
| Freezing Point (FP) Resolution | 0.1°C (0.1°F) |
| Freezing Point (FP) Accuracy | ±0.5°C (±1.0°F) |
| Temperature Range | 0.0 to 80.0°C (32.0 to 176.0°F) |
| Temperature Resolution | 0.1°C (0.1°F) |
| Temperature Accuracy | ±0.3°C (±0.5°F) |
| Automatic Shut-Off | after three minutes of non-use |
| Battery Type / Life | 9V / approximately 5000 readings |
| Enclosure Rating | IP65 |
| Dimensions | 192 x 102 x 67 mm (7.6 x 4.01 x 2.6”) |
| Weight | 420 g (14.8 oz.) |
| Refractometer Light Source | yellow LED |
| Refractometer Temperature Compensation | automatic between 10 and 40°C (50 to 104°F) |
| Minimum Sample Volume | 100 ?L (to cover prism totally) |
| Sample Cell | stainless steel ring and flint glass prism |
| Measurement Time | approximately 1.5 seconds |
| Ordering Information | Supplied with battery and instruction manual. |
| Warranty | 2 years |
