Colored methylthymol blue

Species analysis is performed with various analytical methods, and some examples are described in the following section. Sulfate can be determined depending on the amount in various waters (drinking, surface, waste and saline waters), either colorimetri-cally after reaction with chloranilate in forming the colored acid chloranilate ion, automated as methylthymol blue, as barium sulfate either gravimetrically or nephelometri-cally (turbidimetric) and directly with IC... 

At this stage the solvent is 40% ethanol, the pH is acidic, and the color is light orange. Complexation of barium by methylthymol blue is not a rapidly reversible process (21) indeed sulfate ion will not readily remove barium from its methylthymol blue complex in basic solution. To avoid this problem the reagent is initially acidic, allowing only negligible chelation of the barium until the precipitation of the barium sulfate is completed. 

Methylthymol Blue (3,3 -bis-(N,N-dicarboxymethyl)aminomethylsulfo-naphthalene), a metallochromic indicator, shows a yellow color and forms a deep blue chelate with scandium in acid conditions. At pH 1.5, this color reaction is selective. ... 

Procedure. One drop of the test solution is mixed with one drop of a pH 1.5 buffer solution and then with one drop of a 0.02 % aqueous solution of Methylthymol Blue on a spot plate or in a micro test tube. A blue color indicates the presence of scandium. 

Sulphate, chloride (Cl ), nitrate (NO ), and ammonium (NH ) in water were measured with a Technicon Autoanalyzer II system by the methylthymol blue, mercuric thiocyanate, cadmium reduction and sodium nitroprusside methods, respectively. Sulphate and Cl in highly colored samples were measured by means of ion chromatography. Cations were analyzed with an atomic-absorption spectrophotometer by means of flame-emission spectrophotometry for potassium (K ) and... 

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