Karl Fischer & Potentiometric Titration Application Library
Base number in Lubricant oil (Perchloric acid / Back-titration) | Autotitrator COM-A19
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 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 by Potentiometric 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, measurement with procedure B will be applied.
Acid number in Refrigerating machine oil | Autotitrator COM-A19
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.
Base number in lubricating oil (Perchloric acid method) | Autotitrator COM-A19
・ JIS K2501 2003 : Petroleum products and lubricants – Determination of neutralization number
・ ASTM D2896-06 : Standard Test Method for Base Number of Petroleum Products by Potentiometric 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 be applied. 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”.
Base number in lubricating oil (Hydrochloric acid method) | Autotitrator COM-A19
・ 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.
Acid number in Lubricating oil | Autotitrator COM-A19
The acid number of lubricant oil is one of the important index for judging its quality.
Measurement of acid number is defined in several standard test methods. It is indicated by “milligrams of potassium hydroxide required to neutralize acidic components contained in 1 g of the sample”.
The international standard methods for acid number are shown as bellow.
・ JIS K2501 2003：Petroleum products and lubricants – Determination of neutralization number
・ ASTM D664-1995 : Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration
The potentiometric titration process is as follows:
1) Weigh sample exactly corresponding to acid number and dissolve it in a titration solvent.
2) Immerse glass electrode and reference electrode.
3) Start titration with alcoholic potassium hydroxide 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.
