What are the methods of measuring refractive index?
Whether you work with chemicals, foods, beverages, or other products, measuring the refractive index of the products is essential to be at the top of the sales game. Determining the refractive index helps manufacturers maintain process control and set upper and lower limits on the refractive index of their products. In this blog, we’ll delve into the whereabouts of refractive index measurement and why it’s important for the purity check of your product.
Introduction to Refractive Index Testing
Refractive Index Testing or Refractometry measures any particular object’s refractive index and assesses its purity and composition. The governing principle of this method is how light is refracted when it passes through a given substance to determine the concentrations of solutions and chemicals. A Refractive Index testing lab in India uses Snell’s law or the Law Of Refraction to measure the refractive index.
It measures the ratio of the speed of light in a vacuum to the speed of light in another substance. Though the speed of light is the same in a vacuum, when it passes through other media, it gets absorbed and re-emitted by the atoms in the material. Typically, labs use a refractometer to measure the extent to which light is absorbed/bent when it moves from air into a sample to determine the refractive index of a liquid sample.
Types of refractometers:
Handheld refractometers– The traditional analog instrument for measuring a liquid’s refractive index
Digital refractometers- Produce more accurate readings than traditional ones and are equipped with automatic temperature compensation
Abbe refractometer- High accuracy instrument capable of measuring liquid and solid samples
Inline Process Refractometer- The refractometer produces a digital and analog output ready for transmission to a controller
Requirements for refractive index measurements
The refractive index can be measured between 1.30 and 1.71 at a wavelength of 589.3 nm, using an Abbe refractometer. The instrument uses the total reflection method to determine refractive index values. Manual Abbe refractometers and handheld refractometers are also used but the total reflection method minimizes operator influence and time while enhancing accuracy.
Refractive Index Measurement:
What It Is and Its Role in Industry Definition of Disinfection
Testing labs in Chennai use refractive index measurement to determine the purity and concentration of gases, liquid, semi-liquid and solid samples. While gas and solid samples demand high-accuracy instruments for measuring refractive index, a digital refractometer is used to determine the refractive index values for liquids and semi-liquid samples with high precision. Various industry categories take the help of refractive index measurements to characterize different samples:
Food and beverage: Helps in measuring the sugar content of soft drinks
Chemical: Determines the freezing point, acid/base concentration and the presence of organic solvent and inorganic salt
Pharma: Checks for the presence of hydrogen peroxide and methanol
To elaborate, below are some of the essential commodities that take the help of refractive measurement to measure their purity:
For Flavour and the essential oil industry
- Perfumes
- Skin cleansers
- Lotions
- Lemon, lime, orange
- Palm
- Creams
- Waxes
- Natural oils
- Sandalwood
Food and beverage
- Seed oils
- Soybean oils
- Candy
- Syrups
- Dairy products
- Edible oils
- Coffee extracts
- HRCS
- Juices
- Juice concentrates
- Fruit products
- Confections
- Starch
- Milk
- Hydrolysis products
- Vegetable products
- Teas
- Sodas
- Sauces
- Soups
- Jams
- Jellies
- Soft drink
Sugar industry
- Cane sugar
- Beet sugar
- Invert sugar
- Liquid sugar
- Confectionery sugar
- Brown sugar
Petroleum industry
- Oil based paints
- Fine chemicals
- Fluranes
- PET
- Polymers
- Resins
- Solvents
- Plastics
Method of determining the refractive index
The leading Refractive Index testing lab in Chennai uses an Abbe refractometer to determine the refractive index of any substance. The wavelength of the light beam is of primary importance in measuring the refractive index. Different substances have different refractive indices depending on the wavelength used. To measure the value, first, the apparatus is provided with a water jacket to control the temperature of measurements. The manufacturer’s instructions relating to a given light source must be followed according to the directions mentioned in Indian Standards. Finally, to achieve accuracy, the apparatus should be calibrated against distilled water (has a refractive index of 1.3325 at 25°) or any reference liquid as per standards. To mention, the more the refractive index of a sample deviates from its published value, the less pure it is.
At Tamilnadu Test House, one of the best-rated Refractive Index testing lab, we use the latest refractometers and technologies to determine the purity of your products. Our assured results help you establish yourself as a trusted brand in the market while gaining you a competitive edge. Contact us for your requirements.