Sunday, August 23, 2020

pH OF WATER

pH of water by standard method.

 DETERMINATION THE pH OF WATER


pH are one of  most important chemical properties. pH of water are measured according to specified standards. pH of water for drinking find as follows:

pH title image

PRINCIPLE:-

The pH is measured by the pH electrode which is a combined glass electrode. It consists of a combination of sensors of  half-cell and reference half-cell, to an electrode system. The half-cell sensor is a thin pH sensitive semi permeable membrane, which is used to separating two solutions, viz., the outer solution of the sample is to be analyzed and the internal solution encompass inside the glass membrane and has a known pH value. An electrical potential is generated inside and another electrical potential may be generated outside, the difference in the inner and outer potential need to be measured and is given as the pH of the sample.

INSTRUMENTS:

  • pH meter
  • Beaker
  • REAGENT: 
  • Buffers Solutions of known pH value 


SAMPLE HANDLING AND PRESERVATION 

Preservation of sample is not practical. Because biological activities will keep on after a sample has been taken, changes may occur during handling and storage. The characteristics of the water sample may change during sampling and preservation. To reduce the change in characteristics of samples taken for the determination of pH, keep samples at 4°C. Do not allow the samples to freeze. Analysis should begin as soon as possible.

PROCEDURE: 

Three major steps are involved in the experiment. They are 

1. Preparation of Reagents 

2. Calibrating the Instrument 

3. Testing of Sample 


STEPS: 

1. To determine the pH of a water sample, firstly need to calibrate the pH meter using standard pH solutions. The process of  calibration should depend on the pH range according to the Indian standard. 

2. In a clean dry 100 mL beaker take the water sample and place it in a magnetic stirrer, insert the teflon coated stirring bar and stir well. 

3. Now place the electrode in the beaker containing the water sample and check for the reading in the pH meter. Wait until you get a stable reading. 

4. Take the electrode from the water sample, wash it with distilled water and then wipe gently with soft tissue.


The pH of the sample = .......................


ph chart image


PRECAUTIONS 

The following precautions should be observed carefully: 

1. Temperature affects at two points at the time of taking readings. The first is caused by the change in electrode output at different temperatures. The second is the change of pH identified in the sample at different temperatures. This type of error may be depend upon the sample and cannot be controlled manually; hence both the pH and temperature at the time of analysis should be noted. 

2. In general, the glass electrode unable to determined physical properties, like color, high salinity, colloidal matter, oxidants, turbidity or reductants. 

3. If Oil and grease are present in the electrode layer, should be removed by gentle wiping or detergent washing smoothly by hand, followed by rinsing with distilled water, because it may effect the electrode response. 

4. Before using, the electrode should placed in dilute hydrochloric acid solution for at least 2 hours. 

5. The Electrodes of the pH meter are highly breakable in nature, hence handle it carefully. 




Information Civil

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