Color measurements
48
NANOCOLOR
®
UV
/
VIS
II and
NANOCOLOR
®
VIS
II V 1.1 / 10.2017
5.6.5.2
Hess-Ives color unit
The Hess-Ives color index is calculated as follows from four absorbances at the wavelengths
640 nm, 560 nm, 470 nm and 460 nm according to DGK 0.50.2:
𝐻 − 𝐼 =
(𝑅+𝐺+𝐵)×6
𝑑
Formula 3
𝑅 = 43,45 × 𝐸
640
Formula 4
𝐺 = 162,38 × 𝐸
560
Formula 5
𝐵 = 22,89 ×
𝐸
460
+𝐸
470
2
Formula 6
In this case, d is the layer thickness in mm.
5.6.5.3
ICUMSA sugar color
The coloring of sugar solutions is calculated according to ICUMSA GS1/3-7 from absorbance
at 420 nm as follows:
𝐼𝐶𝑈𝑀𝑆𝐴 = 1000 ×
𝐸
420, 50 𝐵𝑟𝑖𝑥
𝑐×𝑏
Formula 7
In this case, c is the concentration of the sugar solution in g/mL and b is the layer thickness
in cm. The ZERO reference is distilled water.
5.6.6
Color scales from L*a*b* or XYZ values
For the Gardner color index there is a DIN EN ISO conversion method from CIE L*a*b*
values. This makes it the only color index for which normalized calculation rules exist!
Furthermore, the ASTM color index and the Saybolt color index are calculated from L*a*b*
values. The ADMI color index is defined through
E values of platinum-cobalt solutions
against distilled water.
5.6.6.1
Gardner color index
The Gardner color index can be applied to all colorations, ranging from 1 (lightest value) to
18 (darkest value) and is measured in 10 mm cuvettes. The Gardner color indexes are
defined by the CIE chromaticity coordinates x and y. All of the color indexes are defined by a
calibration, and the decimal places are calculated by a complex calculation of the x and y
values of the next and the previous measuring points. For more detailed information, please
refer to EN ISO 4630-2. As part of the calculations of the Gardner color index, the software
checks the Y-value against the information provided by the standard EN ISO 4630-2: 2004. If
the value is outside the permitted range, the instrument will display an exclamation mark in
addition to the measured value. This indicates that the sample is either too bright or too dark
for the analysis according to the standard. The ZERO reference is distilled water.
5.6.6.2
ASTM color index
The ASTM color index is defined by the CIE standard color values X, Y, Z, and is therefore
suitable for all colors. It ranges from 0.5 (lightest value) to 8 (darkest value) in increments of
0.5. If the reading is between two values, the color value of the darker value is given with the
prefix "L" (for lower). This calibration applies to 32.5 mm cuvettes and is based on the
standard ASTM D1500-07. You can use 20 mm or 50 mm cuvettes; the software
automatically converts the measurements to 32.5 mm layer thickness.
𝐴𝑆𝑇𝑀 = 0,25 + 0,8695 × (∆𝑋 + ∆𝑌 + ∆𝑍)
Formula 8
∆𝑋 = −log (
𝑋
98,074
)
Formula 9
Summary of Contents for NANOCOLOR UV/VIS II
Page 1: ......
