Potassium conduction, determination

The phenomenon of ion exchange has been confirmed by chemical analysis Films were exposed to potassium chloride solutions of increasing pH, ashed and their potassium content determined by flame photometry. It was found that the potassium content of the films increased as the pH of the solutions rose until saturation was reached at a value which corresponded to that of the change-over in the mechanism of conduction. It was concluded that the change-over in the mechanism of conduction corresponded to the point at which the exchange capacity of the film had reached its limit. 

Capillary electrophoresis Capillary electrophoresis (CE) is used to analyze sodium, potassium, calcium, and magnesium in water samples. The detection is conducted by reverse absorbance measurements. Sufficient separation of the four cations is established with an electrolyte solution of 5 mM imidazole/6.5 mM a-hydroxyisobutyric acid/2 mM 18-crown-6 ether of pEI 4.1 [42]. CE with a contactless conductometric detector is used to determine small anions and cations in water samples from different sources. 2-(N-Morpholino)ethanesulfonic acid/histidine-based (Mes/Elis) electrolytes are used for direct conductivity detection of anions and cations, while ammonium acetate is used for indirect conductivity determination of alkylammonium salts. Eor the simultaneous separation procedure, involving dual-opposite end injection, an electrolyte consisting of 20 mM Mes/EIis, 1.5 mM 18-crown-6 and 20 mM cetyltri-methylammonium bromide provides baseline separation of 13 anions and cations in less than 6 min [43]. Also CE with a capacitively coupled... 

The electrical conductivities of soln. of potassium chloride have been determined with a great degree of precision since aq. soln. of this salt are commonly used as normal standard liquids for measuring the resistance-constants of the apparatus employed in conductivity determinations. According to C. Deguisne, the coefE, K at in reciprocal ohms is represented by the expression 18)+6( —18) ],... 

Figure 4. Estimates of the potassium-conductance relaxation time, rn, from fits of eqs 2, 3, and 4 with XNa = 0 to admittance determinations at various membrane voltages, similar to those shown in Figure 3. Filled triangles are from fits of the average (AVE) of the real and imaginary parts of eight separate, successive admittance determinations at each voltage. Open circles and squares are from fits of 1 standard deviation added to ( + SD) or subtracted from ( — SD) the real and imaginary parts of the AVE admittance. Intact axon 87-39 in ASW + TTX(1 piM)at 12.5 °C.

D. L. Gilbert and G. Ehrenstein, Effect of Divalent Cations on Potassium Conductance of Squid Axons Determination of Surface Charge, Biophys. J. 9, 447-463 (1969). 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

In this reaction 1 mole of bromate yields six atoms of bromine. Bromine is very volatile, and hence such operations should be conducted at as low a temperature as possible and in conical flasks fitted with ground-glass stoppers. The excess of bromine may be determined iodometrically by the addition of excess of potassium iodide and titration of the liberated iodine with standard thiosulphate solution ... 

The ionic conductivity of complexes of the polymer VIII n=3 with potassium, sodium and cesium thiocyanates were also determined. The conductivity of the polymer complexed with CsSCN is in the order of 10" S cm" at 30 °C, and lO- Scm-i at 90 °C [616]. 

The above discussion does not mean that the use of urease and subsequently the use of an ammonia electrode is not practicable for a urea determination. Unfortunately, the commercial company that produced the urea analyzer, chose a conductivity procedure, which happens to be unsuitable for the laboratory of Neonatology. Had they chosen the ammonia electrode, which happens to be a relatively good electrode, and is especially specific, since only ammonia and not potassium can pass an air space, then the instrument could have been made highly specific for urea. In this case an ammonia determination would be done initially and then subtracted by the computer, from the amount which has been generated subsequently. In any case, with present technology, sensitivity is not adequate to use less than approximately 15fil of serum. 

Next, a series of runs was conducted to determine the effect of various alkali metal hydroxide additions along with the sponge nickel catalyst. The 50 wt. % sodium hydroxide and 50 wt. % potassium hydroxide caustic solution used in the initial test was replaced with an aqueous solution of the alkali metal hydroxide at the level indicated in Table 2. After the reaction number of cycles indicated in Table 2, a sample was removed for analysis. The conditions and results are shown in Table 2. The results reported in Table 2 show the level of 2° Amine in the product from the final cycle. The level of NPA in all of the mns was comparable to the level observed in the initial test. No significant levels of other impurities were detected. 

Solyom has conducted an intercalibration of methods used for the determination of phosphorus in sludges [37]. The methods used to determine phosphorus were that of Koroleff [83] in which the sample is digested with potassium peroxydisulphate and phosphate determined spectro-photometrically. Alternatively a reducing Kjeldahl digestion was used followed by determination of phosphate using molybdate and ascorbic acid. The former method gives somewhat low results. The reducing Kjeldahl method is therefore recommended. 

In the inter-alkali alloys, eutectic equilibria have been observed in a number of systems very low melting points have been determined for instance in the Rb-Na system (L (Rb) + (Na), at 82.5 at.% Rb and —4.5°C) and even lower melting temperatures have been observed in ternary systems. Binary sodium-potassium alloys, liquid at room temperature (at 25°C in a composition range of about 15-70 at.% Na, about 7-57 mass% Na), have a good thermal conductivity and a wide temperature range where they are liquid they may be used in heat-exchange systems. Their extremely high chemical reactivity must of course be taken into account. 

The purity of the hypochlorite may be determined by iodo-metric titration. This titration is run conveniently by weighing out a small portion of the hypochlorite (<0.5 g.) in a 4-ml. vial and then dropping the vial and its contents into an iodine flask containing 20 ml. of glacial acetic acid, 10 ml. of water, and 3 g. of potassium iodide. The titration is then conducted in the usual fashion. 

Instruments based on differential ultraviolet absorption still need to be evaluated, and possibly modified, before their acceptance for monitoring ozone in polluted atmospheres on a nationwide scale. The carb and other air pollution control agencies are currently conducting multiyear programs for evaluating ultraviolet absorption side by side with chemiluminescent and potassium iodide-based instruments, to determine their applicability and needed modification, as well as to ensure continuity in the data base while the older monitoring instruments are being replaced. 

The greater conductivity of an ion-exchanger solution containing the potassium salt of anion XVI in solvent 3-o-nitroxylene (Corning No. 476200) [13a] is a reason for the popularity of this system for electrophysiological measurements using ion-selective microelectrodes [216]. Application of this sensor is so widespread that only reviews and books will be mentioned, for microelectrodes in intracellular measurements [23, 32, 78, 86, 211, 217] and for the determination of K in the intercellular liquid [78]. A working valinomycin microelectrode has also been constructed [166]. 

Sodium and potassium concentration (Na+ should be the main constituent) is higher at Viriato according to a very high anionic concentration and also a high conductivity is determined. 

---