Base number in lubricating oil (Hydrochloric acid method) | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. L2 Oct. 7,2022
Lubricant petroleum products Base number in lubricating oil
(Hydrochloric acid method)

1. Abstract

The base number of lubricant oil is one of the important index for judging its quality. Measurement of base number is defined in several standard test methods. It is indicated by “milligrams of potassium hydroxide equivalent weight to acid required to neutralize basic components contained in 1 g of the sample”. There are two methods of base number, hydrochloric acid method and perchloric acid method. In this article, hydrochloric acid method will be introduced. The international standard methods for base number with hydrochloric acid method are shown as bellow.
 ・ JIS K2501 2003:Petroleum products and lubricants – Determination of neutralization number
 ・ ASTM D4739-2011:Standard Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration
The potentiometric titration process is as follows:
 1) Weigh sample exactly corresponding to base number and dissolve it in a titration solvent.
 2) Immerse glass electrode and reference electrode.
 3) Start titration with alcoholic hydrochloric acid solution.
Inflection point is defined as the end point if it obtained sharply. If it’s not clear, the pH obtained from measurement of buffer solution is defined as the end point. The measurement with the latter end point detection will be introduced here.

2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma Automatic Titrator COM Series
  Electrode : Glass electrode GE-101B
    : Reference electrode RE-201Z
    : Thermistor electrode TE-403
(2) Reagents    
  Titrant : 0.1 mol/L hydrochloric acid in 2-propanol
  Titration solvent : Mixture of 500 mL of Toluene, 495 mL of 2-Propanol and 5 mL of water
  Buffer : Mixture of 10 mL of “Buffer A” and 100 mL of titration solvent, “Buffer A” is regulated in “JIS K 2501”

3. Measurement procedure

(1) Determination of the end point pH
i) Put the stir bar in buffer solution and immerse electrodes.
ii) Read the pH after the pH reading stabilizes within 5 mV or 0.1 pH per minute.
The time required for stabilization is about 5 minutes as a guide.
(2) Measurement of Base number
i) Take 5 g of sample into 200 mL tall beaker and weigh accurately to 0.1 mg digits.
Note that the weight of sample will be changed depending on the base number.
ii) Add 125 mL of titration solvent and dissolve sample by stirrer.
The stirrer speed must be adjusted to avoid the scattering of contents or taking the air into the solution.
iii) Immerse the electrodes and titrate by alcoholic HCl titrant until the end point pH.
Also, perform the blank test with the same procedure of sample measurement.

4. Measurement conditions and results

Examples of titration conditions

Measurement of blank

Cndt No. 47
Method Set
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 120 sec
C.P. mL 0 mL
Direction
T Timer 0 sec
D.P. mL 0 mL
End Point pH 3.71 pH
Over mL 0.1 mL
Max.Vol. 20 mL
ConstantNo. 47
Size 0 g
Blank 0 mL
Molarity 0.1 mol/L
Factor 0.9985
K 0
L 0
Unit mL
Formula D
Digits 3
Auto In Pram. Non
Mode No. 15
Int Time Max 0 sec
Del K 0
Del Sens 0 mV
Int Time 60 sec
Int Sens 0 mV
Brt Speed 2
Pulse 40

 

Measurement of sample

Cndt No. 48
Method Oil1
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 120 sec
C.P. pH 6 pH
Direction
T Timer 0 sec
D.P. pH 6 pH
End Point pH 3.71 pH
Over mL 0.3 mL
Max.Vol. 20 mL
ConstantNo. 48
Size 5.0066 g
Blank 0.018 mL
Molarity 0.1 mol/L
Factor 0.9985
K 56.1
L 0
Unit mg/g
Formula (D-B)*K*F*M/S
Digits 3
Auto In Pram. Non
Mode No. 11
Del mL 0.2 mL
Int Time1 60 sec
Tran Timer 120 sec
Del mL2 0.05 mL
Int Time2 60 sec
Int Time 0 sec
Int Sens 0 mV

 

Measurement results

Measurement of blank

Number of
Measurement
Size
(g)
Titer
(mL)
1 0.020
2 0.015
Avg.
(Blank)
0.018 mL

 

Measurement of sample

Number of
Measurement
Size
(g)
Titer
(mL)
Base number
(mgKOH/g)
1 5.0066 1.786 1.978
2 5.0291 1.770 1.951
3 5.0086 1.747 1.934
Statistic
calculation
Avg.
SD
RSD
1.95 mgKOH/g
0.022 mgKOH/g
1.14 %

 

Examples of measurement curves

Measurement of blank  Measurement of sample

 

5. Note

(1) Management of electrode
  It is recommended to activate the electrodes for about 5 minutes to pure water for each measurement. This is because when glass electrode is used for a long time in a nonaqueous solvent, the response speed and electromotive force decrease. Also potassium chloride crystallizes around the liquid junction of the reference electrode, which causes pH fluctuation.
(2) Maintenance of buret
  When you do not use the equipment for a long time, it is recommended to wash the flow channel of buret with water.

 

Keywords: JIS K2501, ASTM D4739, Lubricant oil, Neutralization number, Base number, Potentiometric titration, Non-aqueous neutralization titration

 

*Some measurement would not be possible depending on optional configuration of system.

Hiranuma aquacounter autotitrator com-a19Lubricant petroleum products

Featured Instruments

Aquacounter Potentiometric Titrator COM-A19 | HiranumaAquacounter Potentiometric Titrator COM-A19 | Hiranuma
Hiranuma Aquacounter Potentiometric Titrator COM-A19 | Hiranuma
Sale price$11,490.00 USD Regular price$12,490.00 USD

Featured Titrators

View all
Aquacounter AQ-300 Coulometric Karl Fischer Titrator | Hiranuma
Hiranuma Aquacounter AQ-300 Coulometric Karl Fischer Titrator | Hiranuma
Sale price$5,800.00 USD Regular price$6,990.00 USD
Aquacounter Volumetric Karl Fischer Titrator MOIVO-A19 | Hiranuma
Hiranuma Aquacounter Volumetric Karl Fischer Titrator MOIVO-A19 | Hiranuma
Sale price$11,990.00 USD Regular price$13,990.00 USD
Aquacounter Coulometric Karl Fischer Titrator MOICO-A19 | Hiranuma
Hiranuma Aquacounter Coulometric Karl Fischer Titrator MOICO-A19 | Hiranuma
Sale price$10,990.00 USD Regular price$12,490.00 USD
Aquacounter Potentiometric Titrator COM-A19 | HiranumaAquacounter Potentiometric Titrator COM-A19 | Hiranuma
Hiranuma Aquacounter Potentiometric Titrator COM-A19 | Hiranuma
Sale price$11,490.00 USD Regular price$12,490.00 USD
Aquacounter AQV-300 Volumetric Karl Fischer Titrator | Hiranuma - JM Science
Hiranuma Aquacounter AQV-300 Volumetric Karl Fischer Titrator | Hiranuma
Sale price$5,800.00 USD Regular price$6,990.00 USD