Potassium second limit

One problem in the determination of second limits is that water, a product of the slow reaction, is also a powerful inhibitor of the explosion. In order to reduce errors due to water formation, much of the earlier work on this limit was carried out with potassium chloride coated vessels. With these, and in vessels coated with certain other salts, the limit is much less sensitive to withdrawal rate than it is with a clean Pyrex or a boric acid coated vessel, for example. Pease [19] first noted that potassium chloride coating produces a marked suppression of the slow reaction rate. More recent work by Baldwin et al. [20, 21], which will be discussed later, suggests that the suppression of the limit at low withdrawal rates in... 

Second limits for 2Hz + O2 in potassium chloride coated vessels... 

The second limits are quite reproducible over long periods using the same apparatus, and the limits from independent investigations also agree well. This is shown by Table 6, wliich quotes limits for stoichiometric mixtures in potassium chloride coated vessels. According to Willboum and Hinshelwood [27] the use of a number of similar coatings (KCl, KI, CsCl, Csl) does not alter the limit much. The results of Lewis and von Elbe [23] and Warren [25] in Table 6 also show that the limit is virtually independent of vessel diameter, provided the latter is greater than 4—5 cm. Clearly the limits are not determined primarily by competition between gas phase and wall effects. 

There have been a number of measurements of the effects of mixture composition and temperature on the hydrogen—oxygen second limits in potassium chloride coated vessels (e.g. refs. 28,14, 23, 25, 30). Typical of the results are the explosion regions shown in Figs. 3 and 4. They all... 

The second important component is the cooling agent or reactor coolant which extracts the heat of fission for some usefiil purpose and prevents melting of the reactor materials. The most common coolant is ordinary water at high temperature and high pressure to limit the extent of boiling. Other coolants that have been used are Hquid sodium, sodium—potassium alloy, helium, air, and carbon dioxide (qv). Surface cooling by air is limited to unreflected test reactors or experimental reactors operated at very low power. 

Potassium is the second most abundant cation in the body and is found primarily in the intracellular fluid. Potassium has many important physiologic functions, including regulation of cell membrane electrical action potential (especially in the myocardium), muscular function, cellular metabolism, and glycogen and protein synthesis. Potassium in PN can be provided as chloride, acetate, and phosphate salts. One millimole of potassium phosphate provides 1.47 mEq of elemental potassium. Generally, the concentration of potassium in peripheral PN (PPN) admixtures should not exceed 80 mEq/L (80 mmol/L). While it is safer to also stick to the 80 mEq/L (80 mmol/L) limit for administration through a central vein, the maximum recommended potassium concentration for infusion via a central vein is 150 mEq/L (150 mmol/L).14 Patients with abnormal potassium losses (e.g., loop or thiazide diuretic therapy) may have higher requirements, and patients with renal failure may require potassium restriction. 

Gotti et al. [42] reported an analytical study of penicillamine in pharmaceuticals by capillary zone electrophoresis. Dispersions of the drug (0.4 mg/mL for the determination of (/q-penicillaminc in water containing 0.03% of the internal standard, S -met hy I - r-cystei ne, were injected at 5 kPa for 10 seconds into the capillary (48.5 cm x 50 pm i.d., 40 cm to detector). Electrophoresis was carried out at 15 °C and 30 kV, with a pH 2.5 buffer of 50 mM potassium phosphate and detection at 200 rnn. Calibration graphs were linear for 0.2-0.6 pg/mL (detection limit = 90 pM). For a more sensitive determination of penicillamine, or for the separation of its enantiomers, a derivative was prepared. Solutions (0.5 mL, final concentration 20 pg/mL) in 10 mM phosphate buffer (pH 8) were mixed with 1 mL of methanolic 0.015% 1,1 -[ethylidenebis-(sulfonyl)]bis-benzene and, after 2 min, with 0.5 mL of pH 2.5 phosphate buffer. An internal standard (0.03% tryptophan, 0.15 mL) was added and aliquots were injected. With the same pH 2.5 buffer and detection at 220 nm, calibration graphs were linear for 9.3-37.2 pg/mL, with a detection limit of 2.5 pM. For the determination of small amounts of (L)-penicillamine impurity, the final analyte concentration was 75 pg/mL, the pH 2.5 buffer contained 5 mM beta-cyclodextrin and 30 mM (+)-camphor-10-sulfonic acid, with a voltage of 20 kV, and detection at 220 nm. Calibration graphs were linear for 0.5-2% of the toxic (L)-enantiomer, with a detection limit of 0.3%. 

While the safe upper limit of QT is not defined, it is suggested that the interval not be permitted to exceed 0.52 seconds during treatment. If dose reduction does not eliminate the excessive prolongation, stop the drug. If concomitant diuretics are needed, consider low doses and the addition or primary use of a potassium-sparing diuretic and monitor serum potassium. 

The reaction of 3-hydroxymethyIpyridine 1-oxide with methyl fluorosulfonate and potassium cyanide provides a direct method for 2,6-dicyanation (75JOC2092). However, the generality of this method is limited by the need for a 3-substituent that can form an anhydrobase. In this example (Scheme 138) the anhydrobase is formed by methylation of the 3-hydroxymethyl group followed by elimination either during or subsequent to attack by the second mole of cyanide. The use of such a powerful methylating agent overcomes... 

Mercury Determine as directed under Mercury Limit Test, Appendix TUB, using the following as the Sample Preparation Transfer 2.0 mL of sample into a 50-mL beaker add 10 mL of water, 1 mL of 1 5 sulfuric acid, and 1 mL of a 1 25 potassium permanganate solution cover with a watch glass boil for a few seconds and cool. 

Sample Preparation Transfer 5 g of sample into a 250-mL Erlenmeyer flask, and continue as directed in the second full paragraph for Sample Solution under Arsenic Limit Test, Appendix IIIB, beginning with add 5 mL of sulfuric acid and a few glass beads. After the sample has been digested and the solution diluted to 35 mL, as directed therein, add 1 mL of a 1 25 solution of potassium permanganate, and mix. 

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