HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

L2Oct. 7.
2022

Base number in lubricating oil(Hydrochloric acid method)

Lubricantpetroleum products
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 ofpotassium hydroxide equivalent weight to acid required to neutralize basic components contained in 1 gof the sample". There are two methods of base number, hydrochloric acid method and perchloric acidmethod. 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 PotentiometricHydrochloric 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 frommeasurement 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 electrodeGE-101B：

Reference electrodeRE-201Z：

Thermistor electrodeTE-403(2) Reagents
Titrant：0.1 mol/L hydrochloric acid in 2-propanolTitration 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” isregulated in “JIS K 2501”

3. Measurement procedure(1) Determination of the end point pHi) 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 numberi) 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 thesolution.
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 conditionsMeasurement of blank

Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mL
Direction
T Timer
D.P. mL
End Point pH
Over mL
Max.Vol.

47Set
11pH1200↓003.71
0.1
20ConstantNo.
SizeBlank
Molaritysec Factor
mL K
L
sec
mL Unit
pH FormulamL DigitsmL Auto In Pram.

470 g
0 mL
0.1 mol/L
0.998500

Mode No.
Int Time Max
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

15000600240Mode No.
Del mLInt Time1Tran Timer
Del mL2Int Time2
Int Time
Int Sens

110.2601200.05
6000sec
mVsec
mVmL
D
3
Non

Measurement of sample

Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. pH
Direction
T Timer
D.P. pH
End Point pH
Over mL
Max.Vol.

48
Oil1
11
pH
120
6
↓
06
3.71
0.3
20sec
pHsec
pH
pH
mL
mL

ConstantNo.
Size
Blank
Molarity
FactorK
L

48
5.0066 g
0.018 mL
0.1 mol/L
0.998556.1
0Unit
FormulaDigitsAuto In Pram.

mg/g(D-B)*K*F*M/S
3NonmL
sec
sec
mLsec
sec
mVMeasurement results
Measurement of blank

Measurement of sample

Number ofSize

Titer

Number ofSize

Titer

Base number

Measurement

(g)

(mL)

Measurement

(g)

(mL)

(mgKOH/g)

1－

0.020

1

5.0066

1.786

1.978

2－0.015

25.0291

1.770

1.951

3

5.0086

1.747

1.934

Avg.
（Blank）

0.018 mL
Statistic
calculation

Measurement of blank

Avg.

1.95 mgKOH/g

SD0.022 mgKOH/g

RSD

1.14 %

Measurement of sample

Examples of titration curves

5. Note(1) Management of electrode
It is recommended to activate the electrodes for about 5 minutes to pure water for each measurement. Thisis because when glass electrode is used for a long time in a nonaqueous solvent, the response speed andelectromotive force decrease. Also potassium chloride crystallizes around the liquid junction of thereference 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.
Keyword：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.