Instrumental measurement methods for yellowish and almost colorless liquids

The APHA, Gardner and Lovibond® color numbers

The method of visual comparison with physical standards has two inherent weaknesses – one is the variation in color standards depending on edition or age, the other is the variables in the human observer. To rule out these weak points, there are instrumental measurement methods for determining the color number. These are samples from the chemical and pharmaceutical industries, but color standards are also used in the wastewater and plastics sectors.

Sample types can be: Lacquers – Oils – Solutions – Suspensions – Fats – Fatty acids – Resins – Syrups – Waxes

To this end, the ASTM, for example, has clearly defined the assignments of the visual standards to the color values measured on the device. In principle, all three color numbers are measured in cuvettes or ISO vials in total transmission (TTRAN), as the samples are transparent liquids. Semi-solid substances such as waxes or Vaseline are analyzed in a molten state.

Measurement of yellowish liquid in 10 mm glass cuvette.

Color measurement of red liquid in 50mm glass cuvette.

Vista with heating element for solid samples that are measured in a liquid state.

Color measurement of yellowish liquid in micro cuvette.

The right device

The Vista spectrophotometer is ideal for measuring these color numbers. This is a double-beam spectrophotometer with diffuse/0° measuring geometry, which can be used to measure liquid samples (and transparent solid samples if required) in transmission with simple handling. This device can be used to examine samples with all layer thicknesses from 10 mm to 50 mm. The selection of the color number, together with the examined layer thickness, is referred to as the index. After the measurement, the color values of the sample and various color scales and indices, in particular the APHA, Gardner and Lovibond® indices, can be read off.

Selection of the cuvette

Depending on the number of colors, different indices are available for cuvettes, ISO vials, microcuvettes and ultra-microcuvettes with path lengths from 10 mm to 50 mm. This means that samples can be reliably measured in various simple or acid- or temperature-resistant plastic or glass cuvettes with the appropriate cuvette holders. The Vista offers the special option of calculating the output value for a coating thickness other than the measured one in order to obtain values in accordance with ASTM, DIN and ISO standards. This often eliminates the need to purchase expensive special cuvettes.

HunterLab-NEWS

Praxisbeispiel Messmethode Lovibond® Farbzahl

Lesen Sie in unserem aktuellen Magazin HunterLab NEWS wie wir mit dem Transmissions-Farbmessgerät Vista Farbzahlen messen, worauf man hinsichtlich der Probenhandhabung achten muss und welche Alternativen es gibt. Außerdem finden sich im Heft weitere spannende Artikel zum Thema Farbmessung von Flüssigkeiten und Feststoffen.

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Conclusion

Liquids from almost colorless to yellowish, yellow-green or reddish, classification and reproduction is simple and standard-compliant with the HunterLab Vista.

 

Would you like to know how we can determine the color values of your sample? Get in touch with us, our spectrophotometry experts look forward to hearing from you.

The blog about color measurement

All about color measurement

The HunterLab Europe company blog keeps you up to date on applications and measurement methods, product presentations and company news. Our spectrophotometry experts regularly give you an overview of the colorful and diverse world of color measurement.
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