HIRANUMA APPLICATION DATA

Automatic Titrator

Data. No L11Jun.6.
2017

Base number in Lubricant oil(Perchloric acid / Back-titration)

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 addition, there are two types of perchloric acid titration, forward-titration and back-titration. In
this article, perchloric acid method with back-titration 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) Add fixed amount of perchloric acid in acetic acid solution to the sample.
4) Start titration with sodium acetate in acetic acid solution.
There are two procedures for perchloric acid titration with back-titration, A and B on ASTM D2896.
Procedure A and B use different titration solvent volume and sample weight. In this article, measurementwith procedure B will be applied.

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

COM Series

One buret

Option: Glass electrodeGE-101B: Reference electrodeRE-201Z

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

Additive: 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 thesolution.
(3) Immerse the electrode and start titration. 4 mL of 0.1 mol/L perchloric acid-Acetic acid standard
solution is added with buret, and the contents of beaker is stirred for 2 min.
(4) Titrate by 0.1 mol/L sodium acetate in acetic acid standard solution.
Also, perform the blank test with the same procedure of sample measurement.

4. Measurement conditions and results
Example of titration conditions(1) Measurement of blanki) Dispense 0.1 mol/L perchloric acid in acetic acid standard solution.
Cndt No.
43
MethodDisp
Buret No.
1
S-Timer0 sec
Disp Vol.
4 mLii) Titration with 0.1 mol/L sodium acetate in acetic acid standard solution.
Cndt No.
45
MethodAutoConstantNo.
45
Mode No.
Buret No.
2Size0 gPre IntAmp No.
1Blank0 mLDel K
D. UnitmVMolarity
0.1 mol/L Del Sens
S-Timer
20 sec Factor
1.006
Int Time
C.P. mL
0 mL K0Int Sens
T Timer
0 sec L0Brt Speed
D.P. mL
0 mLPulse
End Sens
300UnitmL
Over mL
0.3 mL Formula
DMax.Vol.
20 mL Digits
4Auto In Pram.
Non805053240sec
mVsec
mV

(2) Measurement of samplei) Dispense 0.1 mol/L perchloric acid in acetic acid standard solution.
Cndt No.
43Method
DispBuret No.
1S-Timer
0 SecDisp Vol.
4 mLii) Titration with 0.1 mol/L sodium acetate in acetic acid standard solution.
Cndt No.
44MethodAutoConstantNo.
44
Buret No.
2Size
1.0307 g
Amp No.
1Blank
3.979 mL
D. UnitmVMolarity
0.1 mol/L
S-Timer
120 sec Factor
1.006
C.P. mL
0 mL K
56.1
T Timer
0 sec L
0D.P. mL
0 mL
End Sens
300
Unit
mg/g
Over mL
0.3 mL Formula((B-D)*K*F*M)/SMax.Vol.
20 mL Digits
4Auto In Pram.
NonMode No.
Pre Int
Del K
Del Sens
Int TimeInt Sens
Brt SpeedPulse

805053240secmVsecmV

Measurement results
Measurement of blank

Measurement of sample

Measurement

SizeTitet

Measurement

Size

Titer

Base number

number(g)(mL)

number(g)(mL)(mgKOH/g)

1－

3.979

1

1.03071.719

12.375

2－

3.978

2

1.0015

1.779

12.39831.01081.763

12.373

Avg.
（Blank）

3.979 mL
Statistic
calculation

Avg.

12.4

SD

0.0138 mgKOH/g

RSD

0.11 %

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, it causes 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.
Temperature change of 1 ° C causes the titrant volume change of 0.1 %. For accurate measurement, factor
titration and sample measurement should be performed at the same room temperature as much as possible.
(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 titration, Back-titration*Some measurement would not be possible depending on optional configuration of system.