HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

L3Jun.6.
2017

Base number in lubricating oil(Perchloric 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 acid
method. In this article, perchloric acid method will be introduced.
The international standard methods for base number with perchloric acid method are shown as bellow.
・ JIS K2501 2003：Petroleum products and lubricants - Determination of neutralization number
・ ASTM D2896-06 ： Standard Test Method for Base Number of Petroleum Products byPotentiometric Perchloric 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 perchloric acid in acetic acid solution.
There are two procedures for perchloric acid titration, A and B on ASTM D2896. Procedure A and B use
different titration solvent volume and sample weight. In this article, measurement with procedure B will beapplied.
Inflection point is defined as the end point if it obtained sharply. If it’s not clear, back-titration method
could be applied. Back-titration method is mentioned in “HIRANUMA APPLICATION DATA No. L11”.

2. Configuration of instruments and reagents(1) Configuration of instruments.
Main unit: Hiranuma Automatic Titrator

COM SeriesElectrode: Glass electrodeGE-101B: Reference electrodeRE-201Z

Inner solution should be changed; it is described below. to below described(2) Reagents
Titrant: 0.1 mol/L perchloric acid in glacial acetic acid standard solution

Titration solvent: Mixture of 500 mL of glacial acetic acid and 1 L of chlorobenzene.
Refer; Toluene can be used instead of chlorobenzene

Inner solution: Saturated sodium perchlorate in glacial acetic acid

3. Measurement procedure(1) Take 1 g of sample into 100 mL beaker and weigh accurately to 0.1 mg digits.
Note that the weight of sample will be changed depending on the base number.
(2) Add 60 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.
(3) Immerse the electrode and titrate by 0.1 mol/L Perchloric acid-Acetic acid standard solution.
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.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

42Auto11mV
100005000.1
2Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

41Auto11mV
300002000.3
20ConstantNo.
42Size0 gBlank
0 mL
Molarity
0.1 mol/L
sec Factor
1.003
mL K
0sec L0mL
UnitmL
mL Formula
DmL Digits
4Auto In Pram.
Non
Measurement of sample

Mode No.
Pre Int
Del K
Del Sens
Int TimeInt Sens
Brt Speed
Pulse

ConstantNo.
SizeBlank
Molaritysec Factor
mL K
sec L
mL
Unit
mL FormulamL Digits
Auto In Pram.

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

411.0126 g
0.025 mL
0.1 mol/L
1.003
56.1
0

1900053240sec
mV
sec
mV

805053240sec
mV
sec
mV

mg/g
(D-B)*K*F*M/S
4Non

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－

0.025

11.0126

2.227

12.2362－0.025

20.91141.998

12.18131.0073

2.218

12.250Avg.
（Blank）

0.025 mL
Statistic
calculation

Avg.

12.2

SD

0.0366 mgKOH/g

RSD

0.30

mgKOH/g%

Measurement of blank

Measurement of sample

Examples of titration curves

5. Note(1) Management of the 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. Since the electrolyte of the inner solution and the oil sample may adhere
around the liquid junction of reference electrode and cause the fluctuation of the potential. Therefore it isrecommended to clean the liquid junction periodically.
(2) Experiment temperature
Acetic acid used as a solvent for the titrant has a relatively large thermal expansion coefficient, and when
the temperature changes by 1 ° C, the titrant causes a volume change of 0.1 %. For accurate measurement,
factor titration and sample measurement should be performed at the same room temperature as much aspossible.
(3) Preparation of inner solution for reference electrodeThe inner solution of the reference electrode RE-201Z is filled with saturated KCl aqueous solution whenpurchased. For this measurement, it is necessary to replace inner solution to saturated sodium perchlorate
in acetic acid solution. Replacement procedure is described below.
i) Prepare the saturated solution of sodium perchlorate in acetic acid with reagent grade of these.
ii) Discharge inner solution from reference electrode RE-201Z and wash inside it with water and thenacetic acid.
iii) Fill the prepared inner solution into reference electrode from the supply port.
iv) Leave the electrode for one day before use.
Keyword：JIS K2501, ASTM D2896, Lubricant oil, Neutralization number, Base number, Potentiometric titration,
Perchloric acid titration*Some measurement would not be possible depending on optional configuration of system.