Editing Brix (section)

==Measurement==
===Specific gravity===
As specific gravity was the basis for the Balling, Brix and Plato tables, dissolved sugar content was originally estimated by measurement of specific gravity using a [[hydrometer]] or [[pycnometer]]. In modern times, hydrometers are still widely used, but where greater accuracy is required, an electronic [[oscillating U-tube]] meter may be employed. Whichever means is used, the analyst enters the tables with specific gravity and takes out (using interpolation if necessary) the sugar content in [[percent by mass]].

If the analyst uses the Plato tables (maintained by the [[American Society of Brewing Chemists]]<ref>"ASBC Methods of Analysis", ASBC; St. Paul Table 1: Extract in Wort and Beer</ref>) they report in °P. If using the Brix table (the current version of which is maintained by NIST and can be found on their website),<ref name="fbates">{{cite web |url=https://archive.org/details/circularofbureau440bate/page/632 |page=632 |title=Polarimetry, Saccharimetry and the Sugars. Table 114: Brix, apparent density, apparent specific gravity, and grams of sucrose per 100 ml of sugar solutions |last1=Bates |first1=Frederick |date=1 May 1942 |publisher=National Bureau of Standards |access-date=12 October 2018}}</ref> they report in °Bx. If using the ICUMSA tables,<ref>"ICUMSA Methods Book" op. cit. Specification and Standard SPS-4 Densimitry and Tables: Sucrose – Official; Glucose, Fructose and Invert Sugars – Official</ref> they would report in mass fraction (m.f.).

It is not, typically, actually necessary to consult tables as the tabulated °Bx or °P value can be printed directly on the hydrometer scale next to the tabulated value of specific gravity or stored in the memory of the electronic U-tube meter or calculated from polynomial fits to the tabulated data, in fact, the ICUMSA tables are calculated from a best-fit polynomial.

Also note that the tables in use today are not those published by Brix or Plato. Those workers measured true specific gravity reference to water at 4&nbsp;°C using, respectively, 17.5&nbsp;°C and 20&nbsp;°C, as the temperature at which the density of a sucrose solution was measured. Both NBS and ASBC converted to [[apparent specific gravity]] at 20&nbsp;°C/20&nbsp;°C. The ICUMSA tables are based on more recent measurements on sucrose, fructose, glucose and invert sugar, and they tabulate true density and weight in air at 20&nbsp;°C against mass fraction.

===Refractive index===
Dissolution of sucrose and other sugars in water changes not only its specific gravity but its optical properties, in particular its [[refractive index]] and the extent to which it rotates the plane of linearly [[Polarization (waves)|polarized]] light. The refractive index, ''n''<sub>D</sub>, for sucrose solutions of various percentage by mass has been measured and tables of ''n''<sub>D</sub> vs. °Bx published. As with the hydrometer, it is possible to use these tables to calibrate a [[refractometer]] so that it reads directly in °Bx. Calibration is usually based on the ICUMSA tables,<ref>"ICUMSA Methods Book", op. cit.; Specification and Standard SPS-3 Refractometry and Tables – Official; Tables A-F</ref> but the user of an electronic refractometer should verify this.

===Infrared absorption===
Sugars also have known [[infrared]] absorption spectra and this has made it possible to develop instruments for measuring sugar concentration using mid-infrared (MIR), [[Nondispersive infrared sensor|non-dispersive infrared]] (NDIR), and [[Fourier-transform infrared spectroscopy|Fourier transform infrared]] (FT-IR) techniques. In-line instruments are available that allow constant monitoring of sugar content in sugar refineries, beverage plants, wineries, etc. As with any other instruments, MIR and FT-IR instruments can be calibrated against pure sucrose solutions and thus report in °Bx, but there are other possibilities with these technologies, as they have the potential to distinguish between sugars and interfering substances. Newer MIR and NDIR instruments have up to five analyzing channels that allow corrections for interference between ingredients.