Section 6 Adapt a buret titration
Adapt a buret titration method to the digital titrator as follows:
1. Use the equation that follows to calculate the digits necessary to do the buret
method.
Digits necessary = (N
t
× mL
t
× 800) ÷ N
c
Note: The digital titrator dispenses 1 mL per 800 digits on the counter.
Where:
N
t
—Normality of the buret titrant
mL
t
—Milliliters of the buret titrant necessary for an average titration
N
c
—Normality of the digital titrator cartridge
If the number of digits necessary is within the range of 70 to 350, use the
buret procedure as written and replace the buret with the digital titrator.
2. If the number of digits necessary is not within the range of 70 to 350, make
the changes that follow:
• If more than 350, decrease the sample size to decrease the quantity of
titrant necessary.
• If less than 70, increase the sample size to increase the precision.
• If the sample size is changed, adjust the amount of buffering or indicating
reagents used by the same proportion.
3. Use the digital titrator to do the buret method. Record the number of digits
necessary.
4. Convert the digits necessary to the equivalent number of buret milliliters as
follows:
Buret milliliters = Digits necessary × (N
c
÷ (800 × N
t
))
If the sample size was changed, adjust the buret milliliters as follows:
• If the sample size was increased, decrease the buret milliliters.
• If the sample size was decreased, increase the buret milliliters.
Multiply the buret milliliters by any normally used factors to calculate the
concentration (e.g., oz/gal or g/L).
For example, adapt a buret procedure that normally uses about 20 mL of a
0.4 N titrant to the digital titrator. Try an 8.0 N titration cartridge.
Digits necessary = (0.4 × 20 mL × 800) ÷ 8.0 = 800 digits
Decrease the sample size to ¼ the normal size to decrease the digits
necessary to 200. After the titration, calculate the equivalent buret milliliters
with the second equation. If the digits necessary is 205:
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