Chemistry: analytical and immunological testing – Condition responsive control
Patent
1995-07-05
1997-07-01
Warden, Jill
Chemistry: analytical and immunological testing
Condition responsive control
436 50, 436163, 422 62, 422108, 422111, 210743, 55227, 55228, 95 9, 95187, G01N 3508
Patent
active
056437978
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a process of continuously measuring and controlling the pH of an acid liquid, wherein the pH is continuously measured with a glass electrode.
Processes of continuously measuring and controlling the pH with use of glass electrodes are known. In those cases a dual two-phase system comprising glass as a common phase is described as a glass electrode. The voltages which depend on the ion activities are generated on the interfaces of the glass phase, which may also be described as a glass membrane, differently from the usage in electrochemistry. The action of the glass electrode is due to the fact that certain glasses assume with respect to aqueous solutions a potential which depends on the activity of the hydrogen ions in the solution. It is presently believed that that interfacial potential is due to an ion exchange process between the alkali ions of the glass and the protons of the solution in the gel layer developing on the glass membrane. The glass electrode can be used to determine the pH of solutions having a pH between 2 and 12. Outside that range the indicated potential is no longer directly proportional to the hydrogen ion concentration of the solution because errors of the readings in the acid or alkaline regions may occur. Such errors are caused by the chemical composition of the electrode glass. An error of the reading in the acid region will simulate a higher pH and an error of the reading in the alkali region will simulate a lower pH. For this reason the measurement and control of the pH of an acid liquid having a fluctuating pH will not be without problems, particularly if the fluctuating pH of an acid liquid may drop below 2, because this may result not only in an error in the acid region but also in a destruction of the glass electrode.
Published German Application 41 17 382 discloses a process of controlling the pH of an acid scrubbing liquid, which is used at a pH<3 in a scrubbing zone. Acid constituents are removed from flue gas in the scrubbing zone and the scrubbing liquid is circulated at least in part. A partial stream of the scrubbing liquid is continuously mixed with a stream of an alkaline solution having a constant concentration and a constant volume rate and the pH of the mixture is continuously measured with a glass electrode. When the pH of the scrubbing liquid drops below 5, a neutral or alkaline correcting liquid is added to the scrubbing liquid until the pH exceeds 5. But that process has the disadvantage that even relatively small fluctuations of the relatively low pH of the scrubbing liquid will cause the pH at the electrode to change to a value above or below the range from 2 to 12 so that the pH cannot accurately be measured with a glass electrode.
SUMMARY OF THE INVENTION
It is an object of the invention to provide for the continuous measurement and control of the pH of an acid liquid a process in which the pH is continuously measured with a glass electrode and which can reliably be carried out even if the pH of the acid liquid fluctuates in a range of relatively low values.
This object underlying the invention is attained in part when the acid liquid is supplied at a constant rate to contact the glass electrode, base is added at a rate to the acid liquid before it contacts the glass electrode until the pH at the glass electrode is in a pH set point range from 2.5 to 11.5, and any subsequently occurring deviation of the pH at the glass electrode from the pH setpoint range is compensated by a change of the base supply rate. In the process in accordance with the invention the pH of the acid liquid is directly determined from the rage at which the base is required. For a mixture of a strong acid and a strong base, the ionic product of the water is used in the following equations, which can be derived from each other and can be used for technical calculations:
It has surprisingly been found that the process in accordance with the invention can be carried out even in case of relatively large fluctuations of the pH of
REFERENCES:
patent: 4329649 (1982-05-01), Scoates
patent: 4762796 (1988-08-01), Weber et al.
patent: 4940551 (1990-07-01), Riggs et al.
patent: 4945939 (1990-08-01), Maxwell et al.
patent: 5246594 (1993-09-01), Stegemann et al.
Schmidt Hans J.
Stegemann Bertold
Carrillo Sharidan
Striker Michael J.
Warden Jill
LandOfFree
Process of continuously controlling the pH of an acid liquid inc does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process of continuously controlling the pH of an acid liquid inc, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of continuously controlling the pH of an acid liquid inc will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-596248