PH MeterQuestion 1) What is full form of pH?
Answer) pH is denoting, potential of hydrogen or power of hydrogen
Question 2) what is pH value or pH scale.?
Answer) pH is a scale used to specify the acidity or basicity of an aqueous solution:
- lower pH values correspond to solutions which are more acidic in nature while higher values correspond to solutions which are more basic or alkaline.
- pH is the negative of the base 10 logarithm of the activity of the hydrogen ion the pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution.
- A lower pH indicates the higher concentration of hydrogen ions at 25 C° solutions with the pH less than seven are acidic and solutions with the pH greater than seven are basic.
Answer) Answer) Primary pH standard values are resolute using a concentration cell with transmission, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be precise with a glass electrode and a pH meter, or a colour changing indicator.
E= measured potential
E0= standard electrode potential
R= gas constant
T= temperature in kelvins
F= faraday constant
Question 6) What are pH indicators.?
- Visual judgment of the color of a test solution with a standard color map.
- Provides a means to measure pH accurate which is gives more specific measurements to nearest number are possible.
- Universal indicator consists of a mixture of indicators which has a continuous colour change from about pH 2 to pH 10.
- Universal indicator made from one type of absorbent paper who lives with universal indicator.
- Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the equivalent Ph value.
- They consist of a simple electronic amplifier and a pair of electrodes or alternatively a combination electrode. Which is display calibrated in pH units. It usually has a glass electrode and reference electrode or a combination electrode.
- These are rod-like structures usually made of glass with the bulb containing the sensor at the bottom.
- The reference electrode is insensitive to the pH of the solution being collected of a metallic conductor which connects to the display.
- The display consists of a voltmeter which shows voltage in units of pH.
- On captivation of the glass electrode and the reference electrode in the test solution an electrical circuit is completed in which there is a potential difference created and detected by the voltmeter now a day many ph meters use a combination probe constructed with the glass electrode and the reference electrode contained within a single probe.
- The accuracy of the pH measurement system is calibrated slope of should be between 90 to 105 and an offset of zero ±30 millivolt (0.5 pH units at 25 C°)
- As per united states pharmacopoeia the instrument shall be capable of temperature compensating
- The pH sensor convert the pH unit to the millivolt signal at any temperature.
- The precision of the temperature measurement system shall be ± 1 C° the declaration of the temperature measurement system shall be at least 0.1 C°
- Two point calibration
- Multiple point calibration and
- Multiple segment calibration
- The increased flow of the sample across the electrode, results in a faster response time.
- The solution is properly homogenate so no areas of increased or decreased pH exist.
- Clogged electrode junction.
- Non-homogeneous solution.
- Troublesome sample with low ionic strength.
- Non-aqueous sample.
- Calibrated by methods traceable to national institute of standards and technology (NIST) or other national authorities.
- Labeled with a pH value accurate to 0.02 pH units may be used.
- Solutions prepared from ACS reagent grade materials or other suitable materials. The solution prepared from the national institute of standards and technology or other national authorities certified material.
- Buffer solutions that are greater than 12 should be used immediately or should be prepared using freshly boiled water and they should be stored under conditions to minimize carbon dioxide absorption and ingress.