MDL number MFCD00077263. The pKa′ value was determined using a method similar to that of Reilley and Swayer. Description: Bromothymol Blue (BTB) is a pH indicator (pKa approx. Using bromothymol blue you wouldn't be able to distinquish between anacid with pH 4 from an acid with pH 5. PubChem Substance ID 24892083. Computational methods, such as SQUAD (84) 16 and SPECFIT/32, and some new methods 7.1) that is used as a biological slide vital stain to define cell walls or nuclei under the mic... SDS. ,IC10113005EA,IC10113025EA. 1 decade ago. Bromothymol blue is an acidic pH chromoionophore where acid to base change corresponds to its neutral to anionic form, respectively. Bromothymol Blue sodium salt powder Synonym: 3′,3′′-dibromothymolsulfonephthalein sodium salt CAS Number 34722-90-2. Relevance. Solutions of different concentration of the indicator were used. Place three small drops of bromothymol blue solution into each of the 5 cuvettes. For this reason it can be electrostatically immobilized on the surface on anion-exchanger resin like Amberlite IRA 401. Beilstein/REAXYS Number 6887926 . They would both appearyellow. Bromothymol blue, Powder ACS. Indicator: pH Range: pKa: Acid Form: Base Form: Methy Violet: 0.0 - 1.6: 0.8: Yellow: Blue: Thymol Blue: 1.2 - 2.8: 1.6: Red: Yellow: Methyl Yellow: 29. As a pH indicator,bromothymol blue, for example, would be useful between from about pH6.0 to pH 7.6. The pKa can be determined from the spectrophotometric data using different methods. Into each of the cuvettes place 3 mL of the solutions of the various pH values (hydrochloric acid, the buffer solutions with pH values 6.0, 7.0 and 8.0, and sodium hydroxide solution). Explain why the acid - base indicator bromothymol blue turns yellow when added to dilute HCl but blue when added to dilute NaOH. Empirical Formula (Hill Notation) C 27 H 27 Br 2 NaO 5 S . 2. Anonymous. NACRES NA.47 Supplier: MP Biomedicals. Other indicators work in different pH ranges. Spectrophotometric determination of the pKa of Bromothymol Blue. Answer Save. Meloun et al. Determination of the pK_a of Bromothymol Blue Use the following graph to determine the molar absorptivity of Bromothymol blue (BTB)? Ensure that the solutions are mixed well. There is a linear relationship between log ( [ln-]/ [Hln]) and pH. In this experiment, spectrophotometry is employed to measure the pKa of bromothymol blue, an acid-base indicator. The indicator (HIn) is a monoprotic acid and we can represent its dissociation as follows: HIn → H+ + In- … (1) The equilibrium expression for such dissociation can be written as. Molar absorptivity ___ (You will be using this value in your experiment.) Assume a cuvet with a 14.45 mm diameter was used. Chloroform showed the highest affinity for bromothymol blue, followed by methylene chloride, ethylene dichloride, benzene, toluene, and carbon tetrachloride. Given the equation: y= 48048x- 0.0105, find the molar absorptivity and use this value in your experiment. pH = pKa - log ( [HIn] / [In-] ) … (2) Molecular Weight 646.36 . 2 Answers. Acid - Base indicators are either weak acids or weak bases so they exist as molecules in equilibrium with their ions. EC Number 252-169-7. [10] [11] describe multiwavelength analysis and nonlinear least squares regres-sion methods. Favorite Answer. It shows that pH=pKa where [ln-]= [Hln] or hwere ( [ln-]/ [Hln])=1 or where log ( [ln-]/ [Hln])=0.