Automatic turbidimetric titration

• US 4,095,272 A
• Filed: 01/11/1977
• Issued: 06/13/1978
• Est. Priority Date: 01/11/1977
• Status: Expired due to Term

• Current Assignee: Phillips Petroleum Company (ConocoPhillips)
• Original Assignee: Phillips Petroleum Company (ConocoPhillips)
• Inventors: Janzen, G. Jay
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US05/758,524
• Time in Patent Office: 518 Days
• Field of Search: 235/151.12, 235/151.3, 235/151.35, 23/230 R, 23/230 A, 23/253 R, 23/253 A, 23/253 TP, 23/232 R, 23/259, 23/292, 23/255 R, 23/255 E, 204/195 T, 204/1 T, 324/30 R, 324/30 A, 324/30 B
• US Class Current: 700/267
• CPC Class Codes: G06G 7/58 for chemical processes G06G7/75 takes precedence; for physico-chemical processes; for metallurgical processes
• CPC Class Codes: Y10T 436/12 Condition responsive control

Abstract

The turbidity of the medium being titrated is continuously measured and an analog signal representative thereof is differentiated. The resulting first derivative signal is compared with a reference signal to produce a control signal when the derivative signal has a predetermined relationship to the reference signal. A titration end point signal, representative of the amount of titrant added to the medium being titrated in order to achieve said predetermined relationship, is produced responsive to said control signal.

Claims

1. Automatic turbidimetric titration apparatus comprising

means adapted to contain a liquid medium to be titrated;

titrant supply means adapted to introduce a turbidimetric titrant into said medium at a gradual rate;

optoelectronic means adapted to produce an analog measurement signal representative of the turbidity of the medium being titrated;

differentiating means adapted to produce, responsive to said analog measurement signal, a differentiated signal representative of the first derivative of said analog measurement signal;

means adapted to compare said differentiated signal with a reference signal and to produce a control signal when said differentiated signal has a predetermined relationship with said reference signal, said predetermined relationship being representative of the occurrence of the titration end-point; and

means responsive to said control signal adapted to produce a titration end-point signal representative of the amount of said titrant added to the medium being titrated in order to achieve said predetermined relationship between said reference signal and said differentiated signal.

2. Apparatus in accordance with claim 1 wherein said titrant supply mans is adapted to introduce said titrant into said medium at an at least substantially constant rate.

3. Apparatus in accordance with claim 2 wherein said differentiating means is adapted to produce said differentiated signal as being representative of the negative first derivative of said analog measurement signal.

4. Apparatus in accordance with claim 2 wherein said means adapted to produce said titration end-point signal comprises timing means;

means for actuating, at the start of a titration, a timing means and said titrant supply means; and

means for deactuating said timing means responsive to said control signal.

5. Apparatus in accordance with claim 4 wherein said means for actuating comprises electrical power supply means, switching means having a first switching position wherein said electrical power supply means is connected to said timing means and to said titrant supply means and a second switchin portion wherein said electrical power supply means is isolated from said timing means and said titrant supply means, and means for moving said switching means to said first switching position at the start of a titration, and wherein said means for deactuating said timing means comprises means for moving said switching means to said second switching position.

6. Apparatus in accordance with claim 5 wherein said means to produce a titration end-point signal further comprises control means adapted to apply said control signal to said means for deactuating said timing means, and means for enabling said control means responsive to said differentiated signal reaching a predetermined value and then falling back to a lower value.

7. Apparatus in accordance with claim 6 wherein said switching means comprises a switch having said first and second switching positions, and a solenoid means adapted to move said switch from one of said positions to the other of said positions;

wherein said means for moving said switching means to said first switching position comprises a first flip-flop circuit having first and second states and having a first output in said first state of said first flip-flop circuit, means for applying the signal at said first output of said first flip-flop circuit to said solenoid means, and means for resetting said first flip-flop circuit to its first state at the start of a titration;

wherein said means for moving said switching means to said second switching position comprises a conjunctive logic circuit having first and second inputs and an output, means connected to said output of said conjunctive logic circuit to reset said first flip-flop circuit from the first state thereof to the second state thereof, and means for applying said control signal to said first input of said conjunctive logic circuit; and

wherein the output of said means for enabling is connected to said second input of said conjunctive logic circuit.

8. Apparatus in accordance with claim 7 wherein said means for enabling comprises a pulse shaping circuit connected to the output of said differentiating means, a second flip-flop circuit having a clock input and a first output, means connecting the output of said pulse shaping circuit to the clock input of said second flip-flop circuit, and means connecting the first output of said second flip-flop circuit to said second input of said conjuctive logic circuit.

9. Apparatus in accordance with claim 8 wherein said conjunctive logic circuit is a NAND circuit.

10. A method for turbidimetric titration comprising:

introducing a liquid medium to be titrated into a titration zone;

thereafter introducing a turbidimetric titrant into said medium at a gradual rate;

continuously measuring the turbidity of the medium being titrated and establishing an analog measurement signal representative thereof;

producing responsive to said analog measurement signal, a differentiated analog signal representative of the first derivative of said analog measurement signal;

comparing said differentiated analog signal with a reference signal and producing a control signal when said differentiated analog signal has a predetermined relationship with said reference signal, said predetermined relationship being representative of the occurrence of the titration end-point; and

producing, responsive to said control signal, a titration end-point signal representative of the amount of said titrant added to the medium being titrated in order to achieve said predetermined relationship between said reference signal and said differentiated analog signal.

11. A method in accordance with claim 10 wherein the titrant is introduced into said medium at an at least substantially constant rate.

12. A method in accordance with claim 11 wherein said titration end point signal is produced by measuring the time interval between the start of the introduction of titrant into said medium and the production of said control signal.