Chromatic parameters

Fig. 8 pH dependence of the Qy chromaticity parameters obtained during the potentio-metric titration of 1,2-naphthoquinone-2-semicarbazone (NQS) and 1,2-naphthoquinone-2-thiosemicarbazone (NQT). (Data adapted from Ref. 48.)... 

To establish the color change quality of an indicator on an objective basis, the color changes have to be characterized by chromatic parameters. The sequence of color changes of indicators can be described for both CIE and complementary chromaticity systems from the experimental values obtained in indicator solutions, by continuous measurement of the absorbance values at 10 nm intervals between 380 and 770 nm over the pH range of the color change of the indicator, and simultaneously by potentiometric measurement. 

Escolar D, Haro MR, Saucedo A, etal. (1996) Determining acid equilibrium-constants by means of chromatic parameters. Applied Spectroscopy 50 1290-1294. 

Figure 12.1 Chromatic parameters (<3 6 plane of the CIE Lab coordinates) of oxide (a) and non-oxide (b) perovskites proposed as pigments. The numbered fields represent the color space of industrial Inorganic pigments black Fe-Cr-Co-Ni spinel (1), magenta Cr-malayaite (2), pink hematite-zircon (3),...

Speclrophotomelric techniques allow to determine a series of parameters related to skin colour among these are the luminance (the luminous intensity of a surface in a given direction per unit of projected area), reflectance (relation between incident and reflected radiation) or the chromaticity parameters (related to the proportion of basic colours of the visible spectrum that define the colour of the studied sample) (Clarys et al, 2000 Egea, 2005). 

Chemical inhibitors, when added in small amounts, reduce corrosion by affecting cathodic and/or anodic processes. A wide variety of treatments may be used, including soluble hydroxides, chromates, phosphates, silicates, carbonates, zinc salts, molybdates, nitrates, and magnesium salts. The exact amount of inhibitor to be used, once again, depends on system parameters such as temperature, flow, water chemistry, and metal composition. For these reasons, experts in water treatment acknowledge that treatment should be fine tuned for a given system. 

A more recent process, the P2 etch [60], which uses ferric sulfate as an oxidizer in place of sodium dichromate avoids the use of toxic chromates, but still provides a similar oxide surface morphology (Fig. 15) allowing a mechanically interlocked interface and strong bonding [9]. The P2 treatment has wide process parameter windows over a broad range of time-temperature-solution concentration conditions and mechanical testing confirms that P2-prepared surfaces are, at a minimum, equivalent to FPL-prepared specimens and only slightly inferior to PAA-prepared surfaces [61]. 

Chromium zeolites are recognised to possess, at least at the laboratory scale, notable catalytic properties like in ethylene polymerization, oxidation of hydrocarbons, cracking of cumene, disproportionation of n-heptane, and thermolysis of H20 [ 1 ]. Several factors may have an effect on the catalytic activity of the chromium catalysts, such as the oxidation state, the structure (amorphous or crystalline, mono/di-chromate or polychromates, oxides, etc.) and the interaction of the chromium species with the support which depends essentially on the catalysts preparation method. They are ruled principally by several parameters such as the metal loading, the support characteristics, and the nature of the post-treatment (calcination, reduction, etc.). The nature of metal precursor is a parameter which can affect the predominance of chromium species in zeolite. In the case of solid-state exchange, the exchange process initially takes place at the solid- solid interface between the precursor salt and zeolite grains, and the success of the exchange depends on the type of interactions developed [2]. The aim of this work is to study the effect of the chromium precursor on the physicochemical properties of chromium loaded ZSM-5 catalysts and their catalytic performance in ethylene ammoxidation to acetonitrile. 

Carrazza et al (Ref 26) by replacement of both the first fire (DP-973) and the intermediate compns (DP-906) used in the M49A1 Trip Flare Assembly with a W/Ba chromate/K perchlorate/ VAAR (65/24/10/1%) compn (DP-1886). Comparison of the parameters of interest are shown in Table 10... 

Kinetics and activation parameters for the oxidation of phenol with tetrakis(pyridine) cobalt(II) chromate have been determined.16 The oxidation of oximes of cyclopen-tanone, cyclohexanone, and cycloheptanone with pyridinium fluorochromate is first order each in the oxidant and oxime. The observed reactivity sequence has been rationalized on the basis of I-strain.17... 

TCDD in the workers was 217 pg/g blood lipid (range, 33.6-2,252) compared to 3.9 pg/g in the controls (range, 2.9-6.0). There was no significant correlation between the current 2,3,7,8-TCDD concentrations and alterations in any of the immune parameters among the entire exposed group. In addition, the results of the tetanus vaccination and the chromate resistance test were not correlated with... 

---