and the ASBC used slightly different values for the density of air and pure water in their calculations for converting to apparent specific gravity. It should be clear from these comments that Plato and Brix are, for all but the most exacting applications, the same. Note: all polynomials in this article are in a format that can be pasted directly into a spreadsheet. The ICMUSA polynomials are generally only published in the form where mass fraction is used to derive the density. As a result, they are omitted from this section. Refractive index When a refractometer is used, the Brix value can be obtained from the polynomial fit to the ICUMSA table: , where is the refractive index measured at the wavelength of the sodium D line (589.3 nm) at 20 °C. Temperature is very important as refractive index changes dramatically with temperature. Many refractometers have built in "Automatic Temperature Compensation" (ATC) which is based on knowledge of the way the refractive index of sucrose changes. For example, the refractive index of a sucrose solution of strength less than 10 °Bx is such that a 1 °C change in temperature would cause the Brix reading to shift by about 0.06 °Bx. Beer, conversely, exhibits a change with temperature about three times this much. It is important, therefore, that users of refractometers either make sure the sample and prism of the instrument are both at very close to 20 °C or, if that is difficult to ensure, readings should be taken at 2 temperatures separated by a few degrees, the change per degree noted and the final recorded value referenced to 20 °C using the Bx vs. Temp slope information. As solutes other than sucrose may affect the refractive index and the specific gravity differently, this refractive "Brix" value is not interchangeable with the traditional hydrometer Brix unless corrections are applied. The formal term for such a refractive value is "Refractometric Dry Substance" (RDS). See below. Usage The four scales are often used interchangeably since the differences are minor. Brix is primarily used in fruit juice, wine making, carbonated beverage industry, starch and the sugar industry. Plato is primarily used in brewing. Balling appears on older saccharimeters and is still used in the South African wine industry and in some breweries. Oechsle as direct reading for the sugar content is primary used in wine making in Germany, Switzerland and Luxembourg. Brix