Phenol read indicator

The pH is measured colorimetrically with phenol red indicator. High FAC causes lower pH readings due to bleaching of the indicator and resultant HCl formation. The pH of pool water is readily controlled with inexpensive chemicals. Hydrochloric acid solution or sodium bisulfate lower it, whereas sodium carbonate raises it. Since acid addition neutralizes a portion of the alkalinity this must be replenished if the alkalinity drops below the minimum. By contrast, pH adjustment with carbon dioxide does not affect alkalinity. 

The accompanying sketch qualitatively describes the phase diagram for the system nylon-6,6, water, phenol for T > 70°C.f In this figure the broken lines are the lines whose terminals indicate the concentrations of the three components in the two equilibrium phases. Consult a physical chemistry textbook for the information as to how such concentrations are read. In the two-phase region, both phases contain nylon, but the water-rich phase contains the nylon at a lower concentration. On this phase diagram or a facsimile, draw arrows which trace the following procedure ... 

CHjC0.NH C6H N02 +CH,COOH After allowing to stand for 1 hr, add distd w through the condenser in an amt sufficient to hydrolyze surplus anhydride to acetic acid. Transfer to a 1 1 vol flask and dilute to the mark. Pipette an aliquot into a beaker and titrate with N/10 NaOH soln in presence of an indicator, such as phenol-phthalein. Take the burette reading (Rj). Run a blanc by titrating with N/10 NaOH the same quantity of acetic anhydride... 

Medicine has made wide use of phenols in many indications, as we shall see later in this book. Medical publications on peels aboimd in terms that are no longer in use and names of outdated molecules, which makes some texts difficult to read. It is therefore worthwhile taking a quick look at what these terms and compoimds correspond to. 

The screen was displaced until the color in the field of vision was equal to that in the glass cylinder. Previous calibration of the scale with buffer solutions of known hydrogen exponent permitted the pH value to be read directly. This arrangement is very useful for determining pH of water at the location where the sample is collected, since no auxiliary instruments are required. It is evident that this instrument may be used also with other indicators, such as methyl red, methyl orange, etc. Phenol-phthalein may not be used because of the instability of its alkaline solutions. Physiological solutions, such as urine, may be examined rapidly with this instrument. 

Use thin-layer chromatography to obtain an analysis of the product mixture (see Prior Reading). Use methylene chloride as the elution solvent, silica gel (with a fluorescent indicator) as the stationary phase, and UV light for visualization. Typical Revalues are 0.04 for 4-nitrophenol, 0.15 for phenol, and 0.58 for 2-nitrophenol. 

---