Potassium critical values

Combustion, Flames and Explosion in Gases , 2nd Editn, Academic Press, NY (1961), 322—23 (Dust quenching occurs at a critical value of the surface area of the dust per unit vol of the suspension, and depends on the nature of the salt. Better results are obtained with salts having a mp under 200°. Alkali halides are better than carbonates, potassium better than sodium, fluoride better than iodide and better than chlor-ide. If the dust concentration is high enough, even detonation waves can be extinguished)... 

Molecular theory of caustification.—An excess of solid calcium hydroxide is supposed to be present at the start, so that as fast as calcium hydroxide is removed from the soln. by reacting with the potassium carbonate, more passes into soln. Thus the cone, of the calcium hydroxide in the soln. is kept constant. The. solubility of calcium carbonate is very small, and, in consequence, any calcium carbonate in excess of the solubility will be precipitated as fast as it is formed. The reaction proceeds steadily from right to left because, all the time, calcium hydroxide steadily passes into soln., and calcium carbonate is steadily precipitated but the solubility of calcium carbonate steadily increases with increasing cone, of potassium hydroxide. There is a steady transformation of the potassium carbonate into potassium hydroxide in progress The cone, of the potassium carbonate is steadily decreasing, while the cone, of the potassium hydroxide is steadily increasing. Consequently, when the potassium hydroxide has attained a certain cone, so much calcium carbonate will be present in the soln. that the reaction will cease. Hence the cone, of the potassium carbonate should be such that it is all exhausted before the state of equilibrium is reached. If the cone, of the potassium hydroxide should exceed this critical value, the reaction will be reversed, and calcium carbonate will be transformed into calcium hydroxide. 

For the extraction of proteins, aqueous two-phase systems (ATPS) are preferred over organic solvents, which usually denature the proteins and render them biologically inactive. They consist of polyethylene glycol (PEG), and a salt (e.g., potassium phosphate) or dextran in water. At concentrations above a critical value, the mixture separates into two phases—one rich in PEG and the other in dextran or salt. In industrial systems, salts are more commonly used because they are relatively inexpensive as compared to dextran. The MW, charge and surface properties of the protein decide how the protein partitions in the system. The nature of the phase components, the MW of the polymer, and the concentration and type of salt used also affect the distribution. ... 

Side effects. During chloride extraction, hydroxyl ions are formed around the reinforcing steel, locally increasing the pH and sodium and potassium ions are enriched around the steel. These changes might stimulate aUcah-silica reaction (ASR, Section 3.4). In the framework of COST 521, the possibility of ASR was checked as a side-effect of chloride extraction [28,36,80,81]. The aggregates studied were reactive and the alkali content of the cement was just below the critical values. The results obtained with non-carbonated concrete showed that, under the worst conditions, chloride extraction induced concrete expansion, but no cracking was observed. 

The SECM theory for the first-order process was developed [66a] and applied to dissolution of the (100) face of copper sulfate single crystal, while the second-order kinetic model was shown to describe well the dissolution of potassium ferrocyanide trihydrate [66c]. By considering a dislocation-free crystal surface on which dissolution sites are only nucleated above a certain critical value of the undersaturation, one can also model an oscillatory dissolution process [66b]. In all cases, the change in geometry caused by dissolution of the substrate and electrodeposition at the tip was neglected. 

In a different example, traceability in the amount-of-substance analysis of natural potassium, thorium, and uranium by the method of passive gamma-ray spectrometry was demonstrated by Nir-El (1997). For an absolute quantitative determination, accurate values of two parameters were required (i) the emission probability of a gamma-ray in the decay of the respective indicator radionuclides, and (2) the detection efficiency of that gamma-ray. This work employed a number of CRMs in the critical calibration of the detection efficiency of the gamma-ray spectrometer and the establishment of precise emission probabilities. The latter results compared well with literature values and provided smaller uncertainties for several gamma-rays that were critical for the traceabUity claim. The amount-of-substance analytical results of the long lived naturally occurring radionucHdes K, Th, and... 

Normally, the number of anions and cations in each fluid compartment are equal. Cell membranes play the critical role of maintaining distinct ICF and ECF spaces which are biochemically distinct. Serum electrolyte concentrations reflect the stores of ECF electrolytes rather than that of ICF electrolytes. Table 24-4 lists the chief cations and anions along with their normal concentrations in the ECF and ICF. The principal cations are sodium, potassium, calcium, and magnesium, while the key anions are chloride, bicarbonate, and phosphate. In the ECF, sodium is the most common cation and chloride is the most abundant anion while in the ICF, potassium is the primary cation and phosphate is the main anion. Normal serum electrolyte values are listed in Table 24—5. 

More experimental work has been done with DDT than with all the other five chlorinated hydrocarbons combined, probably because DDT was the first of the group found to have insecticidal value. Carter (10) has summarized the several colorimetric methods for DDT. The one proposed by Stiff and Castillo (51), as modified by Claborn (14), and the one by Schechter and Haller (47) have probably been most widely used. In the Stiff and Castillo method, when the DDT is heated in pyridine solution containing xanthydrol and potassium hydroxide, a red color develops which is proportional to the quantity of DDT present. The reaction is sensitive to 10 micrograms. As TDE does not give a color with this reagent, Claborn (14) has proposed the reaction for the determination of DDT in the presence of TDE. He has also shown that for the development of the color the amount of water in the pyridine is critical. 

The peroxide value (PV) of an oil or fat is defined as the quantity of peroxide oxygen present in the sample. This classical iodometric method is a volumetric analysis based on the titration of iodine released from potassium iodide by peroxides in a biphasic system using a standardized thiosulfate solution as the titrant and a starch solution as the indicator (see Background Information, discussion of peroxide value). This method will detect all substances that oxidize potassium iodide under the acidic conditions of the test, therefore the purity of the reagents is critical. 

The wetting properties of polyacetylene have been studied by Schonhom et al. 380) who measured a critical surface tension of 51 mN m 1, considerably higher than for other hydrocarbon polymers. This value was attributed to oxidation of the surface as no change was observed on further oxidation. Treatment of polyacetylene with aqueous potassium permanganate renders it hydrophilic, reduces the contact angle for water from 72° to 10° and renders the structure more water-permeable 381)... 

Prout did not consider himself a proficient experimentalist nonetheless, he designed and carried out experiments to determine the weights of such atoms as iodine, phosphorus, sodium, iron, zinc, potassium, and beryllium. For other elements he accepted the atomic weights that had been measured by scientists he considered trustworthy. Of critical importance was the atomic weight accepted for hydrogen itself and for this Prout used the value measured by Davy. With these data in hand, Prout pro-... 

Therefore, all early studies of copolymerizations must be examined critically when the ring size of any of the comonomers exceeds three. For example, published values of ri and V2 are regarded as having only qualitative significance in studies of the copolymerization of Dq with [CH2 = CH(CH3)SiO]4 initiated by potassium hydroxide at 150 °C 54, 55). These data failed (Saam, unpublished results) the method of analysis of copolymerization data developed by Kelen et al. (53). Likewise quantitative results have little meaning in the copolymerization of D4 with (CH3HSiO)4 and (CH3HSiO)5 initiated by aluminum sulfate at an unspecified temperature (56). For both studies, Dq and D4 appeared to be qualitatively less reactive than their comonomers, but even this conclusion should be made with reservations. 

The significance of these critical ratios was first pointed out by Magnus for ionic complexes and later applied by Goldschmidt to crystals. In the case of GsCl, CsBr and Csl, the value of the ratio rA is greater than 0 73. It is therefore understandable that these salts form crystals with a coordination number of eight. There are, however, many exceptions to the conditions formulated above. For example, the halides of rubidium, potassium chloride and potassium fluoride, which crystallize with a NaCl lattice, have a value of rA greater than 0 732. 

An acid may, rather arbitrarily, be called a strong acid in glacial acetic acid if HAjp - 1- Thus perchloric acid is a strong acid, and yet the pAT for the overall dissociation constant is only 4.87 because it exists largely as ion pairs. Hydrochloric acid has an overall pAT value of 8.55 ammonia, 6.40 pyridine, 6.10 sodium acetate, 6.68 potassium chloride, 6.88 and sodium perchlorate, 5.48. Perchloric acid is the strongest acid and the one used for titration of bases that may be too weak to be titrated in water as solvent. At first it appears that an attempt to titrate a base such as pyridine with perchloric acid would fail, since both have small overall dissociation constants. Critical to the success of such titrations is the small dissociation constant of the salt formed, which results in a large favorable equilibrium constant for the reaction. 

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