JP5641646B2 - Titration device - Google Patents

Description

  The present invention relates to a titration apparatus for performing various titrations such as oxidation-reduction titration and neutralization titration.

  When measuring COD (Chemical Oxygen Demand), which is one of the indicators of water pollution, oxidize organic matter in the sample solution with potassium permanganate and stop the oxidation with excess sodium oxalate. Then, in order to measure the amount of potassium permanganate required for oxidation, back titration is again performed using potassium permanganate.

  The COD automatic measurement apparatus that automatically performs titration as described above includes at least a sample liquid introduction mechanism that introduces a sample liquid into a sample container, a reagent liquid introduction mechanism that introduces a reagent for titration, and the sample after completion of measurement. A liquid discharge mechanism that discharges the liquid in the container and a control device that controls each of the mechanisms are provided.

  The reagent solution introduction mechanism particularly related to the titration includes a titration reagent solution introduction tube inserted into the sample container and a reagent solution discharge tube connected to the titration reagent solution introduction tube, and the discharge or aspiration amount of the reagent solution is controlled by a motor or the like. The amount of reagent dropped onto the sample liquid is controlled by minutely controlling the amount of movement of the pusher by the number of command pulses input to the motor.

As described above, the amount of the reagent solution dropped into the sample solution is accurately controlled. However, for example, when the dropped reagent solution is chemically altered, another substance is added. An error occurs between the amount of the reagent solution to be added by the control and the amount of the reagent solution actually added. Alternatively, a reaction different from that assumed by the presence of a substance different from the original reagent solution in the sample solution results in a decrease in titration accuracy. Specifically, in the automatic COD measurement apparatus, when COD measurement is continuously performed while exchanging the sample solution, permanganic acid that has not been introduced into the sample solution by titration is placed in the reagent solution introduction tube for titration. Because potassium remains, it will continue to be exposed to large amounts of air while not titrating. When potassium permanganate is left in an environment with a large amount of air, the self-decomposition reaction represented by 4KMnO ₄ → 2K ₂ O + 4MnO ₂ + 3O ₂ is promoted and solid manganese dioxide is generated in the tube. May end up. This manganese dioxide has a catalytic effect, so if it exists in a tube or sample container, the amount of potassium permanganate that is added to the sample solution for titration will change to manganese dioxide at an accelerated rate, greatly affecting titration accuracy. Will appear. Further, if manganese dioxide is generated in the titration reagent solution introduction tube, the tube may be clogged, and the titration itself may not be performed in the first place.

  In order to prevent the reagent solution from being deteriorated due to self-decomposition or the like during the waiting time until such titration is started, the tip of the titration reagent solution introducing tube as in the titration device disclosed in Patent Document 1 is used. It is conceivable to prevent the reagent solution from coming into contact with air. In addition, when the tip of the reagent solution introduction tube for titration is placed in the sample solution in this way, the reagent solution can be introduced due to the diffusion effect caused by the contact between the sample solution and the reagent solution. Compared with the titration method by dripping that can only be introduced, the resolution can be further improved and accurate titration can be performed.

  However, if the tip of the reagent solution introduction tube for titration is placed in the sample solution in this way, the minimum amount that can be introduced at the time of titration can be reduced, but the sample solution and the reagent solution contact each other at the time of titration. ing. For this reason, the reagent solution that should have been used for the titration flows out into the sample solution while it is not under control, resulting in a titration error. For example, if the sample solution and reagent solution are in contact with each other during the waiting time such as waiting for oxidation of the sample solution as in COD measurement, the reagent solution will flow out into the sample solution, so titration starts. In this case, some reagent solution has already been added in advance. The amount of unintentional reagent solution outflow due to such contact of each solution is not known, and it is difficult to perform correction, so that it appears as an error during titration. In addition, if there is an environmental change such as a temperature rise near the tip of the reagent solution introduction tube during standby, the reagent solution comes out from the tip as microbubbles existing in the reagent solution expand. Since the amount of outflow is also an amount that cannot be controlled or measured, the accuracy of the titration is deteriorated.

  On the other hand, as a configuration only for preventing deterioration due to self-decomposition of the reagent solution, etc., every time titration is completed as shown in Patent Document 2, without attaching the tip of the reagent solution introduction tube for titration into the sample solution, There is a method of discharging all reagent liquid such as potassium permanganate remaining between the syringes from the tip of the titration reagent liquid introduction tube. However, as disclosed in Patent Document 2, the titration syringe has a small discharge capacity and cannot discharge all of the reagent liquid inside the titration reagent liquid introduction tube. And the piping needs to be complicated, and the configuration of the titration apparatus becomes complicated.

Japanese Patent Laid-Open No. 11-108917 JP-A-2005-195212

  The present invention has been made in view of the above-described problems, and even if the titration is continuously performed while exchanging the sample liquid, the reagent liquid in the titration reagent liquid introduction tube is on standby until the titration starts. Can be prevented with a simple structure, and even if there is a tip of the titration reagent solution introduction tube in the sample solution, unintentional outflow of the reagent solution is prevented, and titration is performed. Provided is a titration apparatus capable of preventing deterioration of accuracy.

  That is, the titration apparatus of the present invention includes a sample container in which a sample liquid is stored, a sample liquid introduction mechanism that introduces the sample liquid into the sample container, and a reagent liquid that introduces a reagent liquid for titration into the sample container A titration apparatus comprising: an introduction mechanism; a liquid discharge mechanism that discharges liquid from the sample solution; and a control device that controls introduction of the sample liquid and the reagent liquid into the sample container and discharge from the sample container. The reagent solution introduction mechanism is inserted into the sample container, and the tip of the reagent solution is provided below the liquid level when the sample solution is stored in the sample container. An introduction tube, and a reagent solution pump section for discharging or aspirating the reagent solution in the titration reagent solution introduction tube, and the control device controls the liquid discharge mechanism to discharge the liquid from the sample container. After that, the reagent solution pump part The so performed, characterized in that to form a predetermined length by the gas layer from the tip to the reagent liquid introducing pipe for the titration.

  In such a case, after draining from the sample container after completion of the titration, the reagent solution pump unit performs a suction operation, and a gas layer is formed in the titration reagent solution introduction tube by a predetermined length from the tip. Therefore, even if a sample liquid is newly introduced for the next titration, the sample liquid and the reagent liquid do not come into contact with each other. Accordingly, no titration error occurs due to the reagent solution flowing out by contact with the sample solution during the waiting time until the titration is started after the reagent solution pump is operated. Furthermore, during the waiting time, the reagent solution in the titration reagent solution introduction tube contacts only a slight amount of oxygen in the gas layer between the sample solution and the sample solution in the sample container. It is possible to prevent the liquid from being altered by oxidation or the like. In addition, since heat or the like applied to the sample liquid as a preparation for starting titration during the waiting time is hardly transmitted to the reagent liquid by the gas layer, minute bubbles existing in the reagent liquid expand. As a result, the reagent solution can be prevented from coming out of the tube. In addition, since a gas layer is only formed at the tip of the titration reagent solution introduction tube by the suction operation of the reagent solution pump unit, a pump having a large discharge capacity is provided separately so that all the reagent solutions in the tube can be discharged. This is unnecessary, and the reagent solution pump used for titration can be used as it is, so that the configuration of the titration apparatus can be prevented from becoming complicated.

  Even when the sample liquid is heated as a preliminary preparation before the titration operation, the heat is used to prevent the reagent liquid from expanding outside the tube due to expansion of bubbles in the reagent liquid. As a typical embodiment, the apparatus further includes a reaction tank in which the sample container is inserted and the sample solution is heated, and the control device extends from the tip of the titration reagent solution introduction tube to the outside of the sample solution. Examples thereof include those configured to form a gas layer having a length.

  In order to prevent the reagent solution from flowing out from the titration reagent solution introduction tube into the sample solution during the standby time due to the expansion of bubbles even when the sample solution is heated reliably, The titration reagent solution introduction tube is inserted into the sample vessel through the heating tank, and the control device introduces the titration reagent solution. What is necessary is just to be comprised so that the gas layer of the length from the front-end | tip of a pipe | tube to the outer side of the said reaction tank may be formed. If it is such, the inside and the outside can be insulated by the lid, and it is possible to prevent heat from being applied to the reagent solution and to prevent the reagent solution from flowing out during the standby time.

  In order to maintain the titration accuracy while forming a gas layer in the titration reagent solution introduction pipe during the waiting time and maintaining the titration accuracy, The titration may be started after being discharged by the same amount as the amount sucked by the reagent solution pump.

  As described above, according to the titration apparatus of the present invention, after the liquid is discharged from the sample container, the reagent liquid pump unit is operated to perform a suction operation so that a predetermined length of air is drawn from the tip of the titration reagent liquid introduction tube. Since it is configured to form a layer, there is no contact between the sample solution and the reagent solution during the waiting time until the sample solution is newly introduced and titration is started. Therefore, it is possible to prevent the reagent solution from flowing out during the standby time and the unexpected outflow due to the influence of heat from the outside, and to prevent the occurrence of an error factor during titration. In addition, since the gas layer is formed by the reagent solution pump unit used for titration, it is not necessary to provide a separate pump or the like, and it is possible to prevent complication of the configuration of the titration apparatus and increase in manufacturing cost.

1 is a schematic configuration diagram of a COD automatic measurement apparatus according to an embodiment of the present invention. The flowchart which shows the flow of the whole COD measurement in the embodiment. The flowchart which shows the flow of the operation | movement regarding the titration in the same embodiment. The schematic diagram which shows the operation | movement regarding the titration at the time of the drainage process in the embodiment. The schematic diagram which shows the operation | movement regarding the titration from the sample liquid introduction process to an oxidation stop process in the embodiment. The schematic diagram which shows the operation | movement regarding the titration at the time of the titration start and titration process in the embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The titration apparatus of this embodiment is used as a COD automatic measurement apparatus 100 that measures COD (chemical oxygen demand), which is one of water quality indicators. More specifically, the COD measurement is continuously performed while changing the sample solution based on the procedure defined in JIS.

  That is, as shown in FIG. 1, the COD automatic measuring apparatus 100 of the present embodiment includes a reaction tank 1 in which a sample container 11 for storing a sample container 11 is housed, and a sample liquid for introducing the sample liquid into the sample container 11. The introduction mechanism 2 and the reagent solution introduction mechanism 3 for introducing various reagent solutions used for COD measurement into the sample container 11 and the liquid from the sample container 11 to the outside after the COD measurement is completed for a certain sample solution. And a liquid discharge mechanism 4 for discharging. Further, a control device 5 for controlling the introduction and discharge of the sample container 11 and the reagent liquid into the sample container 11 by controlling the sample liquid introduction mechanism 2, the reagent liquid introduction mechanism 3 and the liquid discharge mechanism 4 in sequence. It is provided.

  Briefly describing each part, the reaction tank 1 includes a heat transfer body 12 into which a sample container 11 for storing a sample solution is inserted, a sheet heater 13 for heating the heat transfer body 12, as shown in FIG. And a lid 14 provided to cover the heat transfer body 12 and the upper surface side of the sample container 11.

  The sample container 11 is a glass container having a cone shape on the bottom surface side and a cylindrical shape on the top surface side, and various platinum tubes 15 for detecting various introduction tubes and titration end points from the opening on the top surface into the sample container 11. In addition, a stirring blade 16 and a liquid discharge pipe 41 are inserted. In the sample container 11, the sample is only present on the bottom-side portion that has a cone shape (substantially inverted conical shape), that is, the portion whose cross-sectional area increases from the bottom surface side to the top surface side. The liquid is stored so that a certain level of liquid can be obtained even if the amount of the sample liquid is small. By doing in this way, even if there is little sample liquid, the said measurement electrode 15 and the stirring blade 1616 can be immersed in a sample liquid. Further, since the cross-sectional area is maximized at the opening on the upper surface, it is possible to prevent the devices from interfering with each other even when the various devices described above are inserted, and to be easily inserted into the sample container 11. .

  The heat transfer body 12 is made of metal and has a rotating body shape whose longitudinal cross section is substantially M-shaped, and is recessed in a cone shape in which the sample container 11 is accommodated on the upper surface. And a recess 121 for heat dissipation is formed on the bottom surface. That is, since the concave portion 121 is formed, the center portion on the bottom surface side of the heat transfer body 12 protrudes in a cone shape, and a space is formed between the member forming the side surface. By forming the recess 121 in this way, the heat capacity is reduced and the surface area is increased to improve the cooling efficiency in the oxidation stop process described later. The sheet heater 13 is wound around the outer peripheral surface of the heat transfer body 12, and the substantially flat cylindrical lid 14 is attached to the upper surface of the heat transfer body 12 so as to hermetically cover the sample container 11. is there. That is, the heat generated by the sheet heater 13 is conducted to the sample container 11 through the heat transfer body 12 to heat the sample liquid. Further, heat for heating the sample solution is prevented from being transmitted to the outside of the reaction vessel 1 as much as possible by the lid body 14.

  The sample solution introduction mechanism 2 is attached by penetrating the lid 14, and the tip of the sample solution introduction mechanism 2 adds dilution water to the sample solution introduction tube 21 inserted into the sample container 11, river water, factory waste water, and the like. And a sample solution delivery section 22 for moving the generated sample solution into the sample container 11 through the sample solution introduction tube 21.

  The reagent solution introduction mechanism 3 introduces various reagents into the sample solution stored in the sample container 11. More specifically, the reagent solution introduction mechanism 3 has two introduction lines with respect to potassium permanganate, and a predetermined amount of permanganate is used to oxidize organic substances in the sample solution. An oxidation line L1 for introducing potassium acid and a titration line L2 for introducing potassium permanganate for back-titration of the amount of potassium permanganate necessary for oxidizing the sample solution are provided.

  The oxidation line L1 includes a reagent solution tank 31 in which potassium permanganate is stored, and a reagent solution metering unit 32 in which potassium permanganate is metered. The reagent solution metering section 32 and the reaction vessel 1 are connected by an oxidizing reagent solution introduction pipe 33 so that potassium permanganate is introduced from the reagent solution metering section 32 into the sample solution. It is. It should be noted that sodium oxalate, silver nitrate, sulfuric acid, and washing water are also introduced in order into the sample container one by one by the same mechanism.

  The titration line L2 includes a reagent liquid tank 31 in which potassium permanganate is stored, a titration reagent liquid introduction pipe 34 inserted into the sample container 11 in the reaction tank 1, and the titration reagent liquid introduction pipe. 34, and a reagent liquid pump unit 35 for discharging or aspirating the reagent liquid in 34. The reagent solution tank 31, the titration reagent solution introduction pipe 34, and the reagent solution pump unit 35 are connected by an electromagnetic three-way valve 36, respectively, so that the respective connections can be switched.

  As shown in FIGS. 1 and 4 to 6, the titration reagent solution introduction tube 34 is arranged so that the tip 341 is below the liquid level in the state where the sample solution is stored in the sample container 11. It is. Further, as shown in the enlarged views of FIGS. 4 to 6, the titration reagent solution introduction tube 34 is arranged so that the tip portion extends in the vertical direction, penetrates the lid body 14, and extends from the lid body 14. It is formed to extend upward by a predetermined distance.

  The reagent liquid pump unit 35 includes a syringe 351 and a motor 352 that controls the movement amount of the pusher of the syringe 351, and the motor 352 can minutely control the movement amount by pulse control. In other words, the pusher is configured to move the potassium permanganate in the titration reagent solution introduction pipe 34 by a desired amount of movement by controlling the amount of pushing or pulling.

  The liquid discharge mechanism 4 includes the liquid discharge pipe 41 whose tip is inserted to the bottom surface of the sample container 11 and a liquid suction mechanism 42 that sucks the liquid in the sample container 11.

  Next, the control device 5 will be described. The control device 5 is a so-called computer including a CPU, a memory, an input / output interface, an A / D, a D / A converter, and the like. The control device 5 controls the movement of various liquids by controlling the sample liquid introduction mechanism 2, the reagent liquid introduction mechanism 3, and the liquid discharge mechanism 4 shown in FIG. And functioning as the titration control unit 52.

  In the following description, the configuration of the sequence control unit 51 and the titration control unit 52 will be described while explaining the operation of the COD automatic measurement apparatus 100 with reference to a flowchart.

  First, the sequence control unit 51 configured to control the COD measurement will be described with reference to FIG.

  The sequence control unit 51 performs a sample liquid introduction process, a pretreatment process, an oxidation process, an oxidation stop process, a titration process, a drainage process, and a washing process in this order. Controls the movement of reagent solution.

  That is, first, in the sample solution introduction step, the sample solution is introduced into the sample container 11 by the sample solution introduction mechanism 2 (step S1), and in the pretreatment step, first, sulfuric acid and silver nitrate are sampled by the reagent solution introduction mechanism 3. A pretreatment is performed to add the chlorine ions in the sample liquid as silver chloride, which is added to the liquid (step S2). In the oxidation step, a predetermined amount of potassium permanganate is added to the sample solution by the reagent solution introduction mechanism 3 (step S3), and the sample solution is heated at 100 ° C. for 30 minutes by the sheet heater 13 of the reaction vessel 1. As a result, the organic material is oxidized and decomposed (step S4).

  Next, in the oxidation stop step, sodium oxalate equivalent to potassium permanganate added in the oxidation step is added to the sample solution by the reagent solution introduction mechanism 3 (step S5), the reaction is completed, and the temperature of the sample solution The system waits until it is cooled to 60 ° C. (step S6).

  Then, in the titration step, potassium permanganate is added to the sample solution in minute amounts from the titration line L2 until the potential between the electrodes of the twin platinum electrode 15 that is voltage-controlled so that a constant current flows is maximized. When the end point of titration is reached, the amount of potassium permanganate consumed in the oxidation step is calculated, and the COD value is calculated based on that value (step S7).

  Thereafter, a drainage process is started to perform COD measurement of another sample liquid that is reserved next, and the liquid in the sample container 11 is sucked and discharged by the liquid discharge mechanism 4 (step S8). During the drainage process, the sample liquid detection unit (not shown) in the control device 5 has the liquid level of the sample liquid lowered in the sample container 11 at least from the height at which the platinum electrode of the biplatinum electrode 15 is provided. Detect whether or not. More specifically, in the post-drainage process in which the sample solution is discharged from the sample container 11, the sample solution detector applies an AC voltage between the platinum electrodes, and the conductivity (electrical conductivity) at that time is applied. Is configured to measure. By applying an alternating current between the platinum electrodes in this way, polarization can be prevented from occurring on the surface of the platinum electrode when it is in the sample solution, and the current value can be measured. In addition, as a specific configuration for detecting the presence or absence of the sample solution, for example, the reference conductivity in river water or factory wastewater used as the sample solution is measured in advance, and the measured conductivity and the reference conductivity are measured. The sample liquid detection unit is configured to make a determination by comparing the two. In this way, by using the biplatinum electrode 15, whether the biplatinum electrode 15 is immersed in the sample liquid, that is, whether the sample liquid is discharged from the sample container 11 and the liquid level starts to decrease. It can be detected without using a photo sensor or another electrode for detection. Accordingly, for example, an abnormality such that silver chloride is clogged in the liquid discharge pipe 41 and the drainage cannot be started can be detected without an additional sensor, and an extra sensor needs to be inserted into the sample container 11. Therefore, the sample container 11 can be downsized.

  Finally, cleaning in the sample container 11 and various mechanisms is performed as a cleaning process, and one round of COD measurement procedure is completed (step S9). Then, returning to step 1, the COD measurement of the next sample solution is continuously performed.

  In parallel with the control of the sequence control unit 51, the titration control unit 52 is configured to control operations related to titration. More specifically, the titration line of the sample solution introduction mechanism 2 is controlled in accordance with various controls by the sequence control unit 51. The following description will be made with reference to the flowchart of FIG. 3 and FIGS. 4 to 6 while paying attention to the operation related to titration, particularly the movement of potassium permanganate in the reagent solution introduction pipe 34 for titration. For the sake of simplicity, the flowchart of FIG. 3 is described with the drainage process of the overall process as the start point and the titration process as the end point. 4 to 6, for ease of understanding, piping other than the titration reagent solution introduction tube 34 is omitted, and the titration reagent solution introduction tube 34 is also described by changing its arrangement and scale. is there.

  As shown in the flowchart of FIG. 3, the titration control unit 52 calculates a COD measurement value relating to a certain sample liquid, and starts a discharge process in which the liquid is discharged from the sample container 11 by the sequence control unit 51 ( Step SS1) First, the electromagnetic three-way valve 36 is controlled so that the titration reagent solution introduction tube 34 and the syringe 351 are connected. Then, a pulse is applied to the motor 352 so that a predetermined amount of the syringe 351 is sucked. Then, as shown in FIG. 4, the liquid level of the reagent solution is raised from the tip 341 of the titration reagent solution introduction tube 34 to the outside of the reaction vessel 1 and above the lid body 14, 342 is formed (step SS2). At this time, the number of pulses at the time of suction is determined in advance, and this number of pulses is also used in the subsequent titration step.

  Next, while the sequence control unit 51 performs from the cleaning process to the oxidation stop process, the titration control unit 52 fixes the position of the pusher of the syringe 351 and makes the gas layer 342 the first length. This is kept as it is (step SS3). Therefore, as shown in FIG. 5, even if a new sample solution is introduced into the sample container 11, the sample solution does not enter the titration reagent solution introduction tube 34 from the tip 341 by the gas layer 342. That is, the sample solution and the reagent solution are not in direct contact between the sample solution introduction step and the oxidation stop step, and the air layer 342 is also capped with the tip 341 by the sample solution. It does not flow into the layer 342 and is a sealed environment. Therefore, during the waiting time of 50 minutes or more until the titration process is started, only limited air comes into contact with the potassium permanganate for titration, so that the self-decomposition reaction of potassium permanganate to produce manganese dioxide. Hardly happens. For this reason, it is possible to prevent the titration reagent solution introduction tube 34 from being clogged with manganese dioxide or causing a titration error due to manganese dioxide during titration. Further, even while the sample solution is heated for 30 minutes in the oxidation step, the potassium permanganate in the titration reagent solution introduction tube 34 is only outside the reaction tank 1 and is heated by the heat during oxidation. Hateful. Therefore, minute bubbles in the reagent solution do not expand, and the reagent solution does not flow out to the sample solution except during titration.

  In parallel with the oxidation step of the sample solution with potassium permanganate, the titration control unit 52 first switches the electromagnetic three-way valve 36 so that the syringe 351 and the reagent solution tank 31 are connected, and sucks the syringe 351. The operation is performed to replenish potassium permanganate inside (step SS4). Next, when the oxidation stop process is completed (step SS5), the electromagnetic three-way valve 36 is switched so that the titration reagent solution introduction tube 34 and the syringe 351 are connected, and the drainage is performed as shown in FIG. By discharging only the amount sucked in the process, the gas layer 342 in the titration reagent solution introduction tube 34 is completely removed, and the sample solution and the reagent solution are brought into contact with each other. Specifically, the titration control unit 52 inputs a pulse so that the same operation as the pulse input to the motor 352 in the draining step can be performed on the discharge side, and allows titration to start (step SS6). Finally, the syringe 351 is driven until the end point of the oxidation-reduction titration is detected by the constant current polarization potential difference method using the biplatinum electrode 15, the pulses from the start state to the end point are counted, and the added permanganic acid Determine the amount of potassium. Then, the amount of potassium permanganate necessary to oxidize the sample solution is calculated from the titration amount, and the COD value is calculated based on the value (step SS7).

  According to the COD automatic measuring apparatus 100 of the present embodiment configured as described above, the gas layer 342 is formed by a predetermined length from the tip 341 in the titration reagent solution introduction pipe 34 except for the titration step. Therefore, it is possible to reliably prevent the reagent solution from flowing into the sample solution and causing a titration error when titration is not performed. In addition, since the syringe 351 used during the titration is used to form the gas layer 342, there is no need to provide a separate pump or the like, and the piping is not complicated, so the titration accuracy is improved with a very simple configuration. Can be made.

  Other embodiments will be described.

  In the above embodiment, the gas layer is formed at the tip of the titration reagent solution introduction tube during the draining process, but the liquid is discharged from the sample container, and the liquid is near the tip of the tube. It doesn't matter if it doesn't exist. For example, the gas layer may be formed during the cleaning process or immediately before the sample liquid introduction process. Further, the length of the air layer is not limited to the length of the embodiment. In short, the sample solution and the reagent solution need not be in direct contact, and the gas layer may be formed from the tip of the tube to the outside of the sample solution. Or you may extend to the outer side of a sample container. Further, the gas layer may be formed longer, and may be determined based on the balance between the time taken to eliminate the gas layer at the next titration and the time allotted to each step of COD measurement. If the gas layer is formed too large, the amount of air that comes into contact with potassium permanganate in the tube becomes large, and it is likely that manganese dioxide is easily formed from potassium permanganate by the autolysis reaction. You may restrict | limit the length of a gas layer based on the production amount of manganese dioxide acceptable from a viewpoint. In addition, instead of counting the pulses after removing the air layer, the titer is calculated by counting the pulses from a certain point in the air layer and subtracting only the pulses used during suction in the drainage process. It doesn't matter.

  The titration apparatus of the present invention is not only used for COD measurement but may be used for other neutralization titration, oxidation-reduction titration, and the like. Further, the titration reagent is not limited to potassium permanganate, and other oxidizing agents may be used.

  In addition, various modifications and combinations of embodiments may be performed without departing from the spirit of the present invention.

100 ... COD automatic measuring device (titration device)
DESCRIPTION OF SYMBOLS 1 ... Reaction tank 2 ... Sample liquid introduction mechanism 3 ... Reagent liquid introduction mechanism 4 ... Liquid discharge | emission mechanism 5 ... Control apparatus 34 ... Reagent liquid introduction pipe | tube 341 for titration ... Tip 35 ... Reagent liquid pump section

Claims (4)

A sample container for storing the sample liquid, a sample liquid introduction mechanism for introducing the sample liquid into the sample container, a reagent liquid introduction mechanism for introducing a reagent liquid for titration into the sample container, and the inside of the sample container A titration apparatus comprising a liquid discharge mechanism for discharging a liquid, and a control device for controlling the introduction of the sample liquid and the reagent liquid into the sample container and the discharge from the sample container,
The reagent solution introduction mechanism is inserted into the sample container, and the tip of the reagent solution introduction tube is provided below the liquid level when the sample solution is stored in the sample container; A reagent solution pump part for discharging or aspirating the reagent solution in the reagent solution introduction pipe for titration,
The control device controls the liquid discharge mechanism to discharge the liquid from the sample container, and then causes the reagent liquid pump section to perform a suction operation, so that a predetermined length from the tip is introduced into the titration reagent liquid introduction tube. A titration apparatus characterized by forming a gas layer and preventing contact between a sample solution and a reagent solution other than during titration. A reaction vessel in which the sample container is inserted and the sample solution is heated;
The titration apparatus according to claim 1, wherein the control device is configured to form a gas layer having a length extending from the tip of the titration reagent solution introduction tube to the outside of the sample solution. The reaction vessel contains the sample container therein, and the reagent solution introduction tube for titration is inserted into the sample vessel through the reaction vessel,
Wherein the controller, configured claim 2 titrator according so as to form an air layer length leading to the outside of the reaction vessel from the front end of the titration reagent solution inlet pipe. The titration apparatus according to claim 1, 2 or 3, wherein the control device is configured to start titration after discharging the same amount as the amount sucked by the reagent liquid pump unit when the gas layer is formed. .