Chemistry: analytical and immunological testing – Including titration or ph determination
Reexamination Certificate
1998-06-24
2001-01-16
Till, Terrence R. (Department: 1744)
Chemistry: analytical and immunological testing
Including titration or ph determination
C436S017000, C436S100000, C073S053050, C252S408100
Reexamination Certificate
active
06174731
ABSTRACT:
FIELD OF THE INVENTION
The invention is intended for pH-metric determination of low acid numbers (AN) in petroleum oils such as Transformer, White or Basic and other oils for which AN≦0.03 mg KOH/g oil (Specification for Unused Mineral Insulating Oils for Transformers and Switchgear, IEC Standard, Geneva, Switzerland, 1982).
BACKGROUND OF THE INVENTION
Standards for AN determination in petroleum oils are based on the acid-base titration techniques in non-aqueous systems (American National Standards D3339-87; International Electrotechnical Commission Standard, 296, 1982). These techniques are time and labour consuming, and difficult for automation. There are used toxic and flammable solvents, for example toluene, as well as non-aqueous alkali titrants which are very sensitive to carbon dioxide contamination from the atmosphere. Difficulties are increasing at the determination of AN≦0.03 mg KOH/g oil (Transformer, White, Basic and other oils). In this case the titration should be carried out in a nitrogen atmosphere and besides the indicator, the colour witness (cobalt nitrate solution) is used also for more correct determination of the end point of the titration (American National Standard D3339-87; International Electrotechnical Commission Standard 296, 1982).
The pH-metric technique developed earlier by us for determination of acid value in vegetable oils and corresponding reagent-precursor (0.20 M triethanolamine in a mixture 1+1 of water and isopropanol, (vol.); Ya. I. Tur'yan, O. Berezin, I. Kuselman and A. Shenhar, Israeli Pat. Appl. 110192, 01.07.94) are free from indicated drawbacks. However, its limit of quantitation is 0.03 mg KOH/g oil. It is sufficient for vegetable oils but it does not satisfy requirements of the petroleum oil analysis.
Another reagent (0.01 M NaOAc in water: Ya. I. Tur'yan, V. F. Pokhodzei and D. A. Krukier, Izv. Vyssh. Uchebn. Zaved., Pisshch. Technol., Krasnodar, USSR, No. 3, 1989, p. 39) was developed for pH-metric acid value determination in aqueous samples. This reagent allowed to decrease the limit of quantitation, but is not suitable for AN determination in oils since acid from oils cannot be extracted completely into an aqueous reagent. The aim of the present invention is to provide a reagent for the pH-metric AN determination in petroleum oils in the range AN≦0.03 mg KOH/g oil.
REFERENCES:
patent: 2953439 (1960-09-01), Elliott et al.
patent: 3580704 (1971-05-01), Pickup et al.
patent: 4098575 (1978-07-01), Matsushita
patent: 4654309 (1987-03-01), Mlinar et al.
patent: 0151278B1 (1985-08-01), None
patent: 110192 (1994-10-01), None
patent: 989476 (1983-01-01), None
Chem Abstract 121:118767a (1994).
Ya. I. Tur'yan, V. F. Pokhodzei and D.A. Krukier, Izv. Vyssh. Uchebn. Zaved.,Pisshch Technol. , Krasnodar, USSR, No. 3, 1989, pp. 39-41.
O. Yu. Berezin, Ya I. Tur'yan, I. Kuselman and A. Shenhar, Talanta, 42, 1995, pp. 507-517.
Avinoam Shenhar
Berezin Oleg Y.
Kuselman Ilya
Strochkova Elena M.
Tur'yan Yakov I.
Schlinder Edwin D.
Snider Theresa T.
State of Israel, The Ministry of Industry and Trade, The Nationa
Till Terrence R.
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