Evaluation of colour changes of screened acid-base indicators

1989 ◽  
Vol 54 (2) ◽  
pp. 346-360
Author(s):  
Karel Lemr ◽  
Milan Kotouček
Keyword(s):  
Computer Assisted ◽  
Total Quality ◽  
Quality Indices ◽  
Colour Difference ◽  
Acid Base ◽  
End Point ◽  
Colorimetric System ◽  
Colour Changes ◽  
Screened Indicators ◽  
Chemical Indicator

Based on computer-assisted calculations, six screened indicators were prepared and used for visual titration end point indication. Three of them were evaluated in terms of objective colour characteristics. Their colour changes were characterized in the CIE-xy (1931) international colorimetric system, by the Helmholtz coordinates, complementary Qx, Qy coordinates, perceptibility and course of the ΔJ/ΔpH = f(pH) function. In addition, new indices were introduced, viz. partial quality indices IE, Ip and Im, related with the colour difference between the two indicator species (IE), their colour purity (Ip) and the experimenter's ability to remember the colour in the titration end point (Im). Summed up, the three indices constitute the total quality index of the chemical indicator It. These indices were employed for comparing the single and the corresponding screened indicators.

Computer-assisted evaluation of iris colour changes in primate toxicity studies

1996 ◽  
Vol 88 ◽  
pp. 92
Author(s):  
Walter Bee ◽  
Friedhelm Vogel ◽  
Rainhart Korte
Keyword(s):  
Computer Assisted ◽  
Toxicity Studies ◽  
Colour Changes ◽  
Iris Colour

Effects of using recycled paper in inkjet printing system on colour difference

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ufuk Yılmaz ◽  
Ahmet Tutus ◽  
Sinan Sönmez
Keyword(s):  
Design Methodology ◽  
Colour Difference ◽  
Recycled Paper ◽  
Yellow Colour ◽  
Content Type ◽  
A Value ◽  
Colour Measurements ◽  
Colour Changes ◽  
Hue Angle ◽  
Printing System

Purpose This study aims to examine the colour changes affecting inkjet prints after the recycling of papers. Design/methodology/approach For recycling, papers prepared with the INGEDE 11p standard are recycled four times. Pulping, storage, flotation, beating and bleaching processes are applied for each recycling, respectively. Inkjet prints are made on the obtained test papers, and colour measurements are made using an X-Rite eXact spectrophotometer according to the ISO 13655:2017 standard. These processes are applied again to the papers which are recycled four times, and the results are analyzed. In addition, the values of ΔE00 ′, ΔL′, ΔH ′ and ΔC′ are calculated according to ISO 11664-6:2014 standard by making some calculations according to obtained the L′a′b′ values. Findings It is determined that the ΔE00 value increases after each recycling in cyan magenta and yellow colour, whereas it decreases in black. The highest ΔE00 value is calculated after the fourth recycling stage is yellow with a value of 8.33. The lowest ΔE00 value detected is black with a value of 0.76 after the fourth recycling stage. This paper observes that the colour with the most variation in hue angle among recycling repetitions is black and the colour with the highest hue angle value is yellow. It is seen that repeating recycling causes increase in the chromatic values of the prints. Originality/value After the fourth recycling stage, colour changes have reached an important point and can cause important printing problems. In this case, the customer’s approval must be obtained to continue printing. This case is valid for ΔE00 values. Colour differences for print contrast, trapping and print chroma values are either not very important or are positive for quality.

Colour variation in standard soil-colour charts

Soil Research ◽  
2005 ◽  
Vol 43 (7) ◽  
pp. 827 ◽  
Author(s):  
M. Sánchez-Marañón ◽  
R. Huertas ◽  
M. Melgosa
Keyword(s):  
Analysis Of Variance ◽  
Colour Difference ◽  
Colour Space ◽  
Perception Threshold ◽  
Colour Variation ◽  
Standard Soil ◽  
Colour Changes ◽  
Cielab Colour

This paper presents colourimetric analyses of 6 standard soil-colour charts (1372 chips) from different manufacturers, editions, and degrees of use. The CIELAB hab, L*, and C*ab were found to have significant (analysis of variance, P < 0.05) variations among tested charts, and the Munsell hue, value, and chroma measured in most chips varied from their notation by as much as 1 unit. This discrepancy can be attributed to printing differences and/or colour fading. The Munsell loci of constant hue and chroma plotted in CIELAB colour space showed that colour fading is not uniform, so that visual steps between neighbouring chips change, and constant hue and chroma lines become deformed. The colour difference between chips identically designated in two charts ranged from 0.94 CIEDE2000 units (above perception threshold) for charts from the same manufacturer and degree of use, to 3.72 CIEDE2000 units for old charts from 2 different manufacturers. Chips from old charts became yellowish, darker, and less saturated. These colour changes are consistent with the responses of 10 observers who, on assessing 10 soil-colour samples, reported Munsell notations to have redder hue, lighter value and greater chroma. Periodic colourimetric checking of soil-colour charts would be advisable in order to avoid mistakes in soil-colour description.

Juglone and Lawsone as Acid-Base Indicators

1977 ◽  
Vol 32 (8) ◽  
pp. 890-892 ◽  
Author(s):  
Krishna C. Joshi ◽  
P. Singh ◽  
G. Singh
Keyword(s):  
Weak Acids ◽  
Acid Base ◽  
Natural Sources ◽  
Ph Values ◽  
End Point ◽  
Weak Bases ◽  
Strong Acids

Juglone and lawsone, both acid-base indicators, obtained from natural sources and give pink and red colours with aqueous alkalies, respectively. Their transition ranges are found to be pH 7.4–8.2 and 2.6–3.4. To establish the transition intervals, a buffer series ranging in the pH values from 2.0–2.2–2.4–2.6–2.8–3.0–3.2–3.4–3.6–3.8–4.0–4.2–4.4–4.6–4.8–5.0–5.2–5.4–5.6–5.8–6.0–6.2–6.4–6.6–6.8–7.0–7.2–7.4–7.6–7.8–8.0–8.2–8.4–8.6–8.8–9.0 has been used. Juglone can be used for the titrations of strong acids with strong bases and weak acids with strong bases and lawsone can be used for the titration of strong acids with weak bases only. Permanancy of the colours at the end point is one of their advantages.

scholarly journals On the Use of the Senses of Taste and Smell in Determining the End Point of an Acid-Base Titration.

1956 ◽  
Vol 10 ◽  
pp. 495-499 ◽  
Author(s):  
E. Rancke-Madsen ◽  
J. A. Krogh ◽  
U. Lundqvist ◽  
Einar Stenhagen ◽  
B. Thorell
Keyword(s):  
Acid Base ◽  
End Point ◽  
Acid Base Titration ◽  
The Senses ◽  
Taste And Smell

Noninvasive continuous monitoring of solid-phase peptide synthesis by acid-base indicator

1988 ◽  
Vol 53 (11) ◽  
pp. 2542-2548 ◽  
Author(s):  
Viktor Krchňák ◽  
Josef Vágner ◽  
Pavel Šafář ◽  
Michal Lebl
Keyword(s):  
Peptide Synthesis ◽  
Continuous Monitoring ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Bromophenol Blue ◽  
Amino Groups ◽  
Acid Base ◽  
Qualitative And Quantitative ◽  
Quantitative Test ◽  
End Point

The course and the end point of the acylation of resin-bound amino groups in solid-phase peptide synthesis was monitored by a novel noninvasive qualitative and quantitative test based on the use of the acid-base indicator bromophenol blue.

Acid-base equilibria of some 7-dimethylamino-3-phenoxazone derivatives

1982 ◽  
Vol 47 (6) ◽  
pp. 1588-1596 ◽  
Author(s):  
Vladimír Dostál ◽  
Milan Kotouček ◽  
Hana Kalašová ◽  
Vladimíra Bryndová ◽  
Jiří Šimek
Keyword(s):  
Methyl Ester ◽  
Dissociation Constants ◽  
Spectral Characteristics ◽  
Acid Base ◽  
Protolytic Reactions ◽  
Colour Changes ◽  
Reagent Grade Purity

The acid-base equilibria of some phenoxazine dyes in aqueous-ethanolic solutions were studied spectrophotometrically. The compounds examined were prepared in reagent grade purity, their main spectral characteristics in UV and VIS reagion were found and their dissociation constants were determined in 41% (m/m) ethanol. For the analytically most interesting derivative, gallocyanine methyl ester (IV), the pK values were measured also in solutions with different proportions of ethanol. The colour changes accompanying the protolytic reactions and the factors governing the phenomena are discussed.

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