Chloride meter

The determination of chloride using an instrument known as a chloride meter is probably the most common application of coulometry in biochemistry. The instrument is designed to generate silver ions electrolytically from a silver anode. These ions are removed from the solution as undissociated silver chloride, which is either deposited on the anode or precipitated in the solution. A low concentration of carrier electrolyte (nitrate ions) permits a small current... 

Because of their coulometric origin, if the end point is well determined, all these methods are absolute and do not need any calibration. Some clinical instruments, such as blood chloride meters, use such Ag generated coulometries. 

Coulometric method. There are several chloride meters commercially available which operate on the following principle silver ions are generated from an electrode at a constant rate and combine with chloride ions in the specimen to form insoluble AgCl. When sufficient Ag+ has been generated to react with all the chloride present, the additional generation of Ag+ from the electrode results in a sudden rise in the conductivity of the solution which can be detected by a set of silver indicator electrodes. 

An analytical technique in which the amount of electricity passing between two electrodes in an electrochemical cell is measured. The chloride meter is an example of a coulometric technique. 

A third source of brine is found underground. Underground brines ate primarily the result of ancient terminal lakes that have dried up and left brine entrained in their salt beds. These deposits may be completely underground or start at the surface. Some of these beds ate hundreds of meters thick. The salt bed at the Salat de Atacama in Chile is over 300 m thick. Its bed is impregnated with brine that is being pumped to solar ponds and serves as feedstock to produce lithium chloride, potassium chloride, and magnesium chloride. Seades Lake in California is a similar ancient terminal lake. Brine from its deposit is processed to recover soda ash, borax, sodium sulfate, potassium chloride, and potassium sulfate. 

It is convenient to titrate the suspended barium salt with 18 N sulfuric acid (approx. 12-14 ml.) to a pH. of 1.5 using a pH meter. After removal of the barium sulfate the slight excess of sulfate ion may be precipitated using barium chloride solution. The end point is taken when several drops of filtrate show no turbidity either upon addition of sulfuric acid or barium chloride solution. 

In order to prepare the monoacetate, the crude diacetate is suspended in 150 cc of methanol and, after adding 1.5 cc, concentrated hydrochloric acid, heated to boiling for 15 minutes in a nitrogen atmosphere. The crude monoacetate mhich separates upon the addition of meter after cooling is filtered off, meshed end dried in vacuo over calcium chloride at room temperature. The pure 17-ecetete, obtained after repeated recrystellizetions from methylene chloride/hexane has a MP of 161° to 162°C. 

Similar to the pH meter, gas meters employ specific ion electrodes. The electrodes generate a potential proportional to the activity of a specific ion in solution. The calibration is achieved in standard solution and results read in mV or concentration in mg/L or ppm on the meter. The water can be adapted to monitor the concentration of carbon dioxide, hydrogen sulfide, ammonia, chloride, calcium, potassium and sodium to name a few. 

In addition to varying in costs, the chemical composition of the water provided from the mains supply also varies between the water companies, as may that between independent supplies within each company s area. The current criterion on potable water quality requires it to be wholesome i.e. it should not create a health hazard, with relatively wide limits on particular constituents. The cost of removing these constituents (e.g. calcium, magnesium, chlorides, iron and silica) increases with concentration and variability. This imposes a cost burden on, for example, the semiconductor and electronic component industries and on the operation of high-pressure boilers. Therefore both the potential cost of metered water supply and the chemical composition of the supply waters may influence future decisions on the water company s area in which an industry may wish to locate. 

The general approach illustrated by Example 18.7 is widely used to determine equilibrium constants for solution reactions. The pH meter in particular can be used to determine acid or base equilibrium constants by measuring the pH of solutions containing known concentrations of weak acids or bases. Specific ion electrodes are readily adapted to the determination of solubility product constants. For example, a chloride ion electrode can be used to find [Cl-] in equilibrium with AgCl(s) and a known [Ag+]. From that information, Ksp of AgCl can be calculated. 

A venturi meter with a 50 mm throat is used to measure a flow of slightly salty water in a pipe of inside diameter 100 mm. The meter is checked by adding 20 cm3/s of normal sodium chloride solution above the meter and analysing a sample of water downstream from the meter. Before addition of the salt, 1000 cm- of water requires 10 cm3 of 0.1 M silver nitrate solution in a titration. 1000 cm3 of the downstream sample required 23.5 cm3 of 0.1 M silver nitrate. If a mercury-under-water manometer connected to the meter gives a reading of 20S mm, what is the discharge coefficient of the meter Assume that the density of the liquid is not appreciably affected by the salt. 

The most important type of mixed solution is a buffer, a solution in which the pH resists change when small amounts of strong acids or bases are added. Buffers are used to calibrate pH meters, to culture bacteria, and to control the pH of solutions in which chemical reactions are taking place. They are also administered intravenously to hospital patients. Human blood plasma is buffered to pH = 7.4 the ocean is buffered to about pH = 8.4 by a complex buffering process that depends on the presence of hydrogen carbonates and silicates. A buffer consists of an aqueous solution of a weak acid and its conjugate base supplied as a salt, or a weak base and its conjugate acid supplied as a salt. Examples are a solution of acetic acid and sodium acetate and a solution of ammonia and ammonium chloride. 

Another chloride reduction process, originally developed by Hunter for titanium tetrachloride and known by his name, uses sodium as the reductant. In this process liquid sodium and titanium tetrachloride are simultaneously metered into a steel retort under an argon atmosphere. The highly exothermic reduction reaction... 

In the production of polyvinyl chloride by the emulsion process, the percentages of catalyst, wetting agent, initiator, and solvent all affect the properties of the resultant polymer. They must be carefully metered into the reaction vessel. The vinyl chloride used must also be very pure. Either the scope must specify that the purchased raw material shall meet certain specifications, or some purification equipment must be installed so that the required quality can be obtained. 

Pure potassium bromide, KBr, which adopts the sodium chloride structure, has the fraction of empty cation sites due to Schottky defects, ncv/Nc, equal to 9.159xl0-21 at 20°C. (a) Estimate the enthalpy of formation of a Schottky defect, Ahs. (b) Calculate the number of anion vacancies per cubic meter of KBr at 730°C (just below the melting point of KBr). The unit cell of KBr is cubic with edge length a = 0.6600 nm and contains four formula units of KBr. 

The formation energy of Schottky defects in NiO has been estimated at 198 kJ mol-1. The lattice parameter of the sodium chloride structure unit cell is 0.417 nm. (a) Calculate the number of Schottky defects per cubic meter in NiO at 1000°C. (b) How many vacancies are there at this temperature (c) Estimate the density of NiO and hence the number of Schottky defects per gram of NiO. 

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