The microcoulometric titrator is based on the microcoulomb principle. The various forms of sulfur (chlorine) in the sample are converted to sulfur dioxide (all HCl) at high temperatures in nitrogen and oxygen and enter the titration cell to produce iodine and sulfur dioxide by electrolysis ( In the pool, silver ion reacts with chloride ions by electrolysis. The microcomputer calculates the total sulfur content of the sample (total chlorine) according to Faraday's law, based on the amount of iodine consumed (the amount of electricity consumed by the generated silver ions). content). The entire analysis process is controlled by a computer. Samples are loaded by the autosampler and the instrument is highly automated.
The microcoulomb titrator adopts the principle of microcoulomb titration technology and consists of a Coulomb amplifier, a titration cell, and a suitable electrolytic system as a "zero balance" closed-loop negative feedback system. The acquisition of the bias voltage data and the control of the cracking furnace temperature are performed by the single-chip microcomputer and are connected to the computer in a serial communication manner so as to realize automatic control of the entire system.
(1) Sulfur working principle
When the system is in equilibrium, a constant I3-concentration is maintained in the titration cell. When SO2 enters the titration cell, it reacts with I3-ion: I3-+SO2+H2O → SO3+2H++3I-
The concentration of I3- in the electrolytic cell decreases, the measuring electrode senses this change, and the changing signal is input to the Coulomb amplifier, and a corresponding current is output from the Coulomb amplifier to the pair of electrolysis electrodes. Electrolytic anode produces I3- consumed by SO2 until the original I3-ion concentration is restored:
3I- → I3-+2e
The amount of electricity consumed during the electrolysis was measured. According to Faraday’s law of electrolysis, the total sulfur content in the sample was obtained.
(2) Chlorine working principle
When the system is in equilibrium, a constant Ag+ concentration is maintained in the titration cell. After the sample is lysed, the organic chlorine is converted to chloride ions and then carried by the carrier gas into the titration cell to react with silver ions:
Ag++Cl- → AgCl
The decrease of the silver ion concentration in the titration cell indicates that the electrode pair indicates the change of this signal, and this changed signal is input to the Coulomb amplifier, and then a corresponding current is output from the Coulomb amplifier to the pair of electrolysis electrodes. The electrolyzed anode produces the Ag+ consumed by Cl-, until the original Ag+ ion concentration is restored, and the electricity consumed when the electro-generated Ag+ is measured. According to Faraday's law of electrolysis, the total chlorine content in the sample can be obtained.
Micro Coulomb Titrator electrolytic cell maintenance:
Should be kept in a cool, air-free place, and the chlorine electrolysis tank must be kept from light.
Keep a certain amount of electrolyte in the electrolysis cell and keep the platinum plate below the liquid surface;
Do not move the reference electrode and ensure that the reference electrode arm is free of air bubbles;
Electrolyte should always be formulated and kept fresh;
Do not allow lotions or acetone to penetrate the reference arm when cleaning the microcoulometric titrator. Otherwise, the entire electrolytic cell must be reinstalled.
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