KARL FISCHER TITRI METER

Purpose : 

Determine the moisture in any sample (powder or liquid)

Scope :

In organic fields, moisture content of different kinds of alcohols, acids, hydrocarbons can be determined under this method. It is also used for determination of moisture content in oils, fats, waxes etc

Procedure :

• Put methanol in the titration vessel & Fill the auto zero burette up to zero level.  Switch ON the K.F titrimeter.

• Remove the moisture content in the methanol as on pressing START K.F reagent will be added automatically till complete moisture is removed from the dry methanol.

• Take known quantity of finally powdered or liquid sample in which moisture is to be determined say (200mg).

• Take burette reading before pressing the START push button switch or you may fill burette to O ml position with K.F

• Now START switch is pressed. K.F reagent will start flowing in the titration vessel (RUN & ADD LED’s will glow).

• This will go on till the END point is reached. At the END point the instrument will wait for 25 to 30 seconds.

• If no moisture is detected within this period the END lamp (Red) will glow and titrations complete.

• Take the final reading of the burette and find out the quantity of K.F reagent used (say 5ml).

 CALCULATION

% Moisture Content =    K.F (ml) x MDF x 100

                                         Weight of the sample (mg)

Where MDF = Moisture determining factor of K.F (normally 5mg/ml) KF (ml) = K.F. Fischer reagent used in ml. If liquid samples are added then weight of the sample (mg) = Vol. of the sample (ml)x Specific gravity of sample

INSTRUMENT PREPARATION :

• Take about 150ml or more of K.F reagent.

• Put K.F reagent in the reservoir bottle. For putting the reagent, lift the burette. Before

• Lifting close the stop cock of the burette.

• After filling the reservoir bottle, connect the black rubber tube from the solenoid to the outlet nozzle of the burette.

• Add K.F grade dry methanol in the titration vessel. The quantity of methanol should be such that electrode plates are immersed in it. Replace the glass plug.

• Switch ON the instrument, the display will show ‘END’. If not press an END push button switch at control unit.

• Adjust the stirrer speed such that the electrode ends do not get exposed.

• Close the opening of the air inlet glass tube of burette with finger and pump air with bellow for filling the burette with K.F reagent from the reservoir. After the burette is filled fully, release the finger.

• Now the instrument is ready for titration.

AUTOMATIC OPERATION :

• Open the stop cock of the burette. Press start push button. ‘END’ goes OFF and RUN and ADD, goes ON. The solenoid opens and K.F reagent start flowing in the titration cell.

• The addition of K.F reagent from burette continues till the first sign of reaching the END point. At this point ADD goes OFF and RUN continues. All red LEDs glow as it reaches END POINT. The instrument remain wait in ‘RUN’ state for about 25 seconds to check for the final END POINT.

• In case moisture is still exist and there is a need for more K.F reagent, ADD appears and solenoid operates to add few more drops of reagent into the titration cell. Otherwise END appears after 25 seconds. Red LED indicates that END point has reached.

• First titration is for nullifying the moisture from the methanol and that due to air in the titration vessel and burette etc. Hence there is no need to take burette reading. Fill the burette back with the reagent.

• Now the instrument is ready for titration of the sample.

MANUAL OPERATION :

• In case the automatic operation fails, the instrument can be operated in manual mode also. This happens very rarely. In automatic mode the status lights are made use of. In manual mode the NULL INDICATOR indicates the END point status.

• Instead of passing the rubber tube through solenoid connect it directly between outlet nozzle of the burette and inlet nozzle of the titration cell. Close the stop cock of the burette.

• When the instrument is ready with methanol in the titration cell, start stirring and press START push button. If the extreme left LED glows.

• Open the stop cock and add a few drops of K.F reagent manually. As the other LEDs start blinking add the reagent in smaller volumes (drops) as the all red LEDs glows, stop adding the K.F reagents.

• Wait for 25 to 30 seconds. If the needle remain towards right, the END point is reached and press END push button. Otherwise add few more drops of reagent, if the needle has already deflected towards left side.

• Needle will move towards right side again and wait For 25 seconds more. The titration is complete if the needle remains on the right side

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