Acid number in Refrigerating machine oil | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. L5 Oct. 7,2022
Lubricant petroleum products Acid number in Refrigerating machine oil

1. Abstract

Refrigerating machine oil is used in a state mixed with refrigerant such as hydrofluorocarbon. The official standard of refrigerant (e.g. JIS K 2211) specifies the acid number test according to JIS K 2501. It is indicated by “milligrams of potassium hydroxide required to neutralize acidic components contained in 1 g of the sample”.

In this article, we apply the color-indicator titration method described in JIS K2501 to automatic titrator, and introduce measurement of acid number in refrigerating machine oil by photometric titration. Acid and base number with color-indicator titration is also regulated in ASTM D974. p-Naphtholbenzein is used as color indicator.

2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma automatic titrator COM Series with photometric unit M type
  Electrode : Interference filter 650 nm
(2) Reagents    
  Titrant : 0.1 mol/L potassium hydroxide in 2-propanol
  Titration solvent : Mixture of 500 mL of Toluene, 495 mL of 2-propanol and 5 mL of water
  Indicator : 1 g of p-naphtholbenzein dissolved in 100 mL of titlation solvent

3. Measurement procedure

(1) Take 20 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 acid number.
(2) Add 100 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 electrodes and titrate by alcoholic KOH titrant. 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. 37
Method B-Cross
Buret No. 1
Amp No. 2
D. Unit T%
S-Timer 60 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.3 mL
Max.Vol. 1 mL
ConstantNo. 37
Size 0 g
Blank 0 mL
Molarity 0.1 mol/L
Factor 0.9775
K 56.1
L 0
Unit mL
Formula D
Digits 4
Auto In Pram. Non
Mode No. 41
Int Time Max 60 sec
Del K 0
Del Sens 0 mV
Int Time 10 sec
Int Sens 20 mV
Brt Speed 2
Pulse 8

 

Measurement of sample

Cndt No. 38
Method B-Cross
Buret No. 1
Amp No. 2
D. Unit T%
S-Timer 60 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.5 mL
Max.Vol. 20 mL
ConstantNo. 38
Size 20.059 g
Blank 0.123 mL
Molarity 0.1 mol/L
Factor 0.9775
K 56.1
L 0
Unit mg/g
Formula (D-B)*K*F*M/S
Digits 4
Auto In Pram. Non
Mode No. 42
Int Time Max 60 sec
Del K 0
Del Sens 0 mV
Int Time 10 sec
Int Sens 20 mV
Brt Speed 2
Pulse 20

Measurement results

Measurement of blank

Measurement
number
Size
(g)
Titer
(mL)
1 0.123
2 0.122
  Average 0.123 mL

Measurement of sample

Measurement
number
Size
(g)
Titer
(mL)
Base number
(mgKOH/g)
1 20.0590 0.151 0.0077
2 20.0084 0.157 0.0093
    Average 0.0085 mgKOH/g

 Examples of measurement curves

Measurement of blank Measurement of sample

 

5. Note

(1) Management of the photometric probe
As the probe is used, it becomes dirty on light path and the transmittance decreases. Therefore it is necessary to wipeout adherents with soft cloth on regular bases.
(2) Maintenance of buret
It is recommended to wash the flow channel of buret with water. This is because alcoholic KOH titrant have a tendency toward crystallization. When not using for a long time, please discharge titrant and then wash flow channel with water.
(3) End point detection
When the endpoint is not detected sharply, it may be due to the absorption of carbon dioxide. In this case, purging nitrogen gas in the head space of the beaker improves end point detection.

 

Keywords: JIS K2211, JIS K2501, ASTM D974, Refrigerating machine oil, Refrigerant, Acid number, Color indicator titration, Photometric titration.
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
Aquacounter COM-300A Potentiometric Titrator | Hiranuma - JM Science
Hiranuma Aquacounter COM-300A Potentiometric Titrator | Hiranuma
Sale price$6,490.00 USD Regular price$6,990.00 USD