1. The pH meter was invented in 1934 to measure the acidity and alkalinity of fluids on a scale from 0 to 14. 2. A pH meter uses two probes - a glass electrode that measures the hydrogen ion concentration and a reference electrode - to measure the voltage difference between the solutions and translate it into a pH value. 3. The pH meter must be calibrated using buffer solutions of known pH before taking measurements, and temperature compensation is required as pH electrodes are temperature sensitive.

1. 
Presenter:Presenter:
Dr S KamalakarDr S Kamalakar
PuripandaPuripanda
DEPT OF SAMHITADEPT OF SAMHITA
SDMCA&HSDMCA&H
pH METERpH METER

2. 
 The pH meter was invented in 1934 by the American chemist Arnold O.
Beckman (1900-2004) to measure the sourness of lemons
 A simple and speedy device to measure the acidity and alkalinity of a fluid.
A pH meter acts as a volt meter that measures the electrical potential
difference between a pH electrode and a reference electrode and displays the
result in terms of the pH value of the solution in which they are immersed.
INTRODUCTION

3. 
 The logarithm of the reciprocal of hydrogen-ion concentration in
gram atoms per litre; provides a measure on a scale from 0 to 14 of the
acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is
more basic and less than 7 is more acidic);
pH
(Potential of Hydrogen)
The formal definition of pH is the
negative logarithm of the hydrogen ion
activity.
pH = -log[H+]

4.  An acid can be defined as a proton donor, a chemical that increases the
concentration of hydrogen ions in solution. HCL----------H+
+ CL-
 A corrosive liquid with a pH less than 7; a solution of in water of a substance
that releases hydrogen ions
 A base can be defined as a proton acceptor, a chemical that reduces the
concentration of hydrogen ions in solution. KOH……..K+
+ OH-
 A corrosive liquid with a pH greater than 7; a solution of in water of a
substance that releases hydroxyl ions
Acids and Bases

5. 
A pH measurement system consists of
High input meter
2 probes
Buffer powder/capsules for calibration
Distil water
pH Meter

6. Probe 2Probe 1

7. 1.Glass electrode: It consists thin bulb of special glass
blown(lithium) at the end of the glass tube,and the bulb is filled with
dilute acid for example decinormal HCL acid connected to a silver
chloride electrode
2.Calomel electrode: It consists of a glass tube containing
saturated KCL connected to platinum wires through mercury (mercury
chloride)
3.Reference junction: typically made of porous ceramic or porus teflon
Probe 1 consists of 3 parts (2 electrodes)
ELECTRODE: A conductor used to make electrical contact with some
part of a circuit
Probe 1
1
2
3

8. Probe 2
CHECKING FOR SOLUTION’S
TEMPERATURE
2 PROBES ARE CONNECTED
TO HIGH INPUT pH
READING MTER

9. 
The act of checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument
BUFFER
POWDER/CAPSULES

10. 1.High input pH reading meter

11. 
 A voltmeter in the probe measures the difference between the voltages of the
two electrodes.
 The meter then translates the voltage difference into pH and displays it on
the screen.
 Before taking a pH measurement the meter must be calibrated using a
solution of known pH.
pH Meter

12. 
 Temperature compensation is connected within the instrument
because pH electrodes are temperature sensitive.
 Temperature compensation only corrects for the change in the
output of the electrode, not for the change in the actual solution.
 Buffers are solutions that have constant pH values and the ability
to resist changes in pH.
 They are used to calibrate the pH meter.
Temperature and Buffers

13. 
 1.The 2 probes should connect to pH reading meter
 Connect the power pack of 230v to the pH meter
 Dip the electrode in a standard solution of pH and set the temparature and take reading
(The 1st probe should be calibrate with different buffer solutions for rule out the errors of the
electrode(buffer solution:buffer powder + distil water).Then should check the solution
temperature with 2nd
probe)
 Remove buffers wash and wipe the electrode and dip it in the desireble solution and take
the reading.
METHOD OF USING

14. 
 An electrical potencial devolops when one liquid is brought into contact with
another one ,but a membrane is needed to keep such liquid aparts
 A ph meter measures essentially the electro – chemicall potencial between a
known liquid inside the glass electrode and unknown liquid outside
 Because the thin glass bulb allows mainly the agile and small hydrogen ions
to interact with the glass,the glass electrode measures the electro chemical
potential of hydrogen ions.
How a pH meter works

15. PH EXAMPLE
0 HCL
1 GASTRIC JUICES
2 LEMON JUICE
3 ORANGE JUICE
4 COLA
5 COFEE
6 RAIN WATER
7 PURE WATER
8 SEA WATER
9 BAKING SODA
10 ANTACIDS
12 DETERGENT
13 OVEN CLEANER
14 NAOH

16. 
 SWEAT…4 -6
 VAGINAL FLUIDS…..4.50 -5
 SALIVA…..6.2 – 7.4
 BLOOD……7.35 – 7.45
 URINE…..MORNING 6.5 – 7,THEN 7.5 – 8.0
 INTESTINAL FLUIDS….7.41
 SEMEN….7.35 – 7.40
 LYMPH …..7.4 – 9.0
 EYE TEARS…7.1 – 7.4
 PANCREATIC JUICES…..8.5
BODY FLUIDS

17. 
THANK U
REFERENCES:
RESEARCH METHDOLOGY FOR AYURVEDIC SCHOLARS-DR.S.SURESHBABU
TABER’S CYCLOPEDIC MEDICAL DICTIONARY EDITION 20
INTERNET
IMAGES COLLECTED FROM RASASHASTRA DEPT SDMCAH