Production Of Hydroxyl Ions Research Articles

Aluminum Removal from Rare Earth Chloride Solution through Regulated Hydrolysis via Electrochemical Method

Due to the coexistence of Al3+ and RE3+ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions.

In-situ methane enrichment of biogas from anaerobic digestion of palm oil mill effluent by addition of zero valent iron (ZVI)

Palm oil mill effluent (POME) is a wastewater effluent that is generated from palm oil milling. Treatment of POME, especially using biological treatment methods, is a challenge as it contains high amounts of organic and sulfur compounds, and it is highly acidic. In this research, the effects of zero-valent iron (ZVI) on the enhancement of methane production from POME via anaerobic digestion were investigated. Furthermore, to identify the reactor operation modes that were suitable for the addition of ZVI, anaerobic digestion of POME was tested in three reaction configurations: batch reactor, fed-batch reactor, and continuous stirred-tank reactor (CSTR). In the batch mode, where acidic POME was fed with 16 g/L of ZVI dose just once, methane production increased by 74%. However, as the oxidation of ZVI under anaerobic conditions led to the production of hydroxyl ions, the pH of the medium continuously increased from approximately 7 to 9, which is not suitable for methanogenesis. In the fed-batch mode that involved intermittent feeding of acidic POME, the pH of the culture media was maintained at 6.8. This is because the extra hydroxyl ions generated from the oxidation reaction of ZVI tended to neutralize the acids in the feeding substrate. In addition, ZVI promoted the production of methane from POME and increased the average methane content in biogas from 62% to 76%. In the CSTR mode, which involved continuous feeding of acidic POME, ZVI increased methane production by 86% (from 1.79 to 3.32 L/day), methane content in biogas from 60 to 75%, and total chemical oxygen demand (tCOD) removal efficiency from 78 to 89 to 88–95%. Thus, the addition of ZVI can be a potential strategy for in-situ methane enrichment of biogas by anaerobic digestion of POME. This is because ZVI acts as a buffer for acid generation and provides extra electrons, ferrous ions, and ferric ions, which promote key microbial activities in the anaerobic digestion process.

A compact bipolar electrochemistry device utilizing a liquid free catholyte and eye visual indication of the reporting event for the determination of antioxidant capacity in real-world samples

Here we report for the first time the development of a compact, closed bipolar electrochemistry (BPE) device for the determination of antioxidant capacity in real-world samples by recording the onset driving voltage at which an eye-visible reporting event at the cathode pole of bipolar electrode (BE) occurs. The BPE cell consists of two distinct anode and cathode compartments that are electrically connected through a platinum wire BE. The anode pole of the BE is covered by a cellulose acetate thin film to prevent the fouling of the surface, while the cathode pole is embedded into an agarose hydrogel containing phenolphthalein, i.e., an acid-base indicator. The method relies on the oxidation of the reducing compounds in the sample by a fixed amount of H2O2 and the electro oxidation of the remaining H2O2 in the anode pole of the BE. This reaction triggers the reduction of water at the cathodic pole accompanied by the production of hydroxyl ions at different, H2O2 concentration-dependent onset driving voltages. The resulting increase of pH at the cathode pole results in the formation of a pink spot (reporting event), which is visible by the unaided eye. The applicability of the BPE device for the determination of antioxidant capacity in fruit juices and sodas is demonstrated. The analytical results, expressed as Trolox (TEAC) or Vitamin C (CVEAC) equivalent antioxidant capacity, correlate well with those obtained by the CUPRAC method.

Electrochemically Induced Precipitation Enables Fresh Urine Stabilization and Facilitates Source Separation.

Source separation of urine can enable nutrient recycling, facilitate wastewater management, and conserve water. Without stabilization of the urine, urea is quickly hydrolyzed into ammonia and (bi)carbonate, causing nutrient loss, clogging of collection systems, ammonia volatilization, and odor nuisance. In this study, electrochemically induced precipitation and stabilization of fresh urine was successfully demonstrated. By recirculating the urine over the cathodic compartment of an electrochemical cell, the pH was increased due to the production of hydroxyl ions at the cathode. The pH increased to 11-12, decreasing calcium and magnesium concentrations by >80%, and minimizing scaling and clogging during downstream processing. At pH 11, urine could be stabilized for one week, while an increase to pH 12 allowed urine storage without urea hydrolysis for >18 months. By a smart selection of membranes [anion exchange membrane (AEM) with a cation exchange membrane (CEM) or a bipolar membrane (BPM)], no chemical input was required in the electrochemical cell and an acidic stream was produced that can be used to periodically rinse the electrochemical cell and toilet. On-site electrochemical treatment, close to the toilet, is a promising new concept to minimize clogging in collection systems by forcing controlled precipitation and to inhibit urea hydrolysis during storage until further treatment in more centralized nutrient recovery plants.

The nitrate reduction process: A way for increasing interfacial pH

This paper is devoted to the electrochemical study of the nitrate reduction in aqueous media. The reduction process allows the production of hydroxyl ions at the electrode surface, increasing the local pH. This process provides a useful tool for the precipitation of metallic oxide/hydroxide such as ZnO. When the interfacial pH was high enough, the chemical equilibrium was shifted towards the crystallization. The nitrate reduction was carried out in the presence of dissolved oxygen. The investigated potential range corresponded to the mixed reduction of oxygen and nitrate where both reactions produced OH− and increased the interfacial pH. In this case, it was shown that the pH could reach a value higher than 12 in 1 M KNO3 instead of 10.4 in the presence of only oxygen. Thus, nitrate reduction was useful for the precipitation occurring at pH higher than 10.4. The electrochemical mechanism was studied by electrochemical impedance spectroscopy in a potential range corresponding to the first step of the oxygen reduction. The stationary current–voltage curve did not highlight any current due to the nitrate reduction. The impedance diagrams revealed two capacitive loops characterizing the reduction process of oxygen, namely the charge transfer process at high frequencies and the diffusion process at low frequencies according to the expectations. In the lowest frequency domain, an inductive loop was observed with an amplitude depending on the potential. It was shown that this response was due to the presence of adsorbed species which blocked a part of the active surface for the oxygen reduction. These adsorbed species came from nitrate reduction even if the stationary current of this reaction was negligible in the corresponding potential range. The decrease of the double layer capacity confirmed this approach.

Effects of iron and iron chelation in vitro on mucosal oxidant activity in ulcerative colitis.

Reactive oxygen species may be pathogenic in ulcerative colitis. Oral iron supplements anecdotally exacerbate inflammatory bowel disease and iron levels are elevated in the inflamed mucosa. Mucosal iron may enhance hydroxyl ion production via Fenton chemistry. Conversely, the iron chelator, desferrioxamine, is reportedly beneficial in Crohn's disease. To assess the in vitro effects of exogenous iron and of iron chelators on the production of reactive oxygen species by colonic biopsies from normal control subjects and patients with ulcerative colitis. Luminol-amplified chemiluminescence was used to measure mucosal reactive oxygen species production both before and after addition in vitro of ferric citrate (100 microM), desferrioxamine (1 mM) and 1,10-phenanthroline (1 mM). Ferric citrate had no effect on the chemiluminescence produced by human colonic mucosa. However, desferrioxamine and phenanthroline reduced chemiluminescence by 47% (n=7, P=0.018) and by 26% (n=10, P=0.005), respectively, in inactive ulcerative colitis, and by 44% (n=9, P=0. 008) and 42% (n=11, P=0.006) in active disease. The lack of effect of ferric citrate suggests that sufficient free iron is already present in inflamed biopsies to drive the Fenton reaction maximally. The effects of desferrioxamine and 1,10-phenanthroline on the chemiluminescence of biopsies from patients with ulcerative colitis suggest that a clinical trial of topical iron chelation in active disease is indicated.

Kinetics of growth and dissolution of calcium hydroxyapatite in suspensions with variable calcium to phosphate ratio

Kinetics of growth and dissolution of calcium hydroxyapatite at constant pH (6.0 and 7.2), and with variable values of the calcium to phosphate mole ratio in solution (0.1<Ca/P<20) are reported. Both processes are shown to be controlled by the polynuclear surface mechanism in which nucleation is expressed as a function of mean-ion activity. For dissolution, the lateral growth rate of nuclei is proportional to the difference between the total concentration of calcium ions in a saturated solution and in the solution, and the rate constant is related to the frequency for a calcium ion to make a diffusion jump into a kink and simultaneously, partially dehydrate. For growth, a newly developed model for the lateral growth rate is applied. This model takes into account that hydroxyl ions are formed at hydroxyl sites slightly below the growing surface by dissociation of trapped water molecules. In this way the lateral growth rate consists of two consecutive reactions, the process of calcium ions entering calcium sites, accompanied by phosphate ions, being delayed by the relatively slow production of hydroxyl ions at hydroxyl sites. The frequency for ion integration is found to be within a factor of 2 of the expected value, 1.6×10 5/s, for both growth and dissolution, both values of pH and all values of Ca/P studied. As this frequency is practically constant, the frequency for a calcium ion to leave a kink decreases as the saturation concentration of calcium decreases. This reflects important changes in the dynamics of the crystal surface. Kinetically determined values for the surface tension are for growth σ=100 mJ/m 2 and for dissolution σ=40 mJ/m 2.

Heparin release from polymer complex

An electro-erodible polyelectrolyte complex was prepared and investigated for a pulsatile drug release system. An insoluble polyelectrolyte complex was formed by combining two water-soluble polymers, poly(allylamine) and heparin. Upon the application of an electric current, a rapid structural change of the complex occurred, dissolving the polymer matrix in proportion to the intensity of an applied electric current. The disruption of ionic bonds in the polymer matrix attached to the cathode and subsequent release of heparin was due to the locally increased pH near the cathode (resulting from hydroxyl ion production). Thus, the release pattern of a model bioactive macromolecule, heparin, followed the applied electric current, primarily due to surface erosion of the polymer matrix.

Preliminary characterization of enterooxyntic activity on the guinea pig oxyntic cell.

Stimuli originating in the small intestine enhance gastric acid secretion, an effect termed the intestinal phase of gastric secretion. A humoral agent, enterooxyntin (EO) may mediate this effect. Mechanical distension of an ex vivo-perfused segment of canine jejunum caused the release of EO measured by cytochemical quantification of hydroxyl ion production (HIP) in guinea pig gastric oxyntic cells, an index of acid secretion. The H2 receptor antagonist, cimetidine (10(-5) M), and diamine oxidase, which hydrolyzes endogenous histamine, reduced HIP by 60% and 48%, respectively. Atropine (10(-5) M), the muscarinic cholinergic antagonist, reduced HIP by 75%. EO-induced HIP was also inhibited partially by the Ca2+ antagonist EGTA (10(-6) M) and by blockade of calcium channels with LaCl3 (10(-6) M). EO does not appear to operate through any single pathway. EO may be a single substance, different from gastrin, or a mixture of substances that have stimulatory effects on the oxyntic cell. Its action on the oxyntic cell is apparently mediated by both histaminergic and cholinergic pathways. Since neither cimetidine nor atropine completely inhibited EO-induced HIP, a direct effect of EO on the oxyntic cell seems likely and appears to depend on Ca2+. Isolation and purification of EO will be necessary to better assess the potency, efficacy, and the detailed cellular mechanisms of EO action.

Isolation and partial characterization of an entero-oxyntin from porcine ileum.

Porcine ileal mucosa was homogenized and freeze-thawed in 0.05 M NH4HCO3 + 0.01 M EDTA + 1 mM benzamidine hydrochloride at pH 8.6. Subsequent stepwise precipitation with (NH4)2SO4 followed by fractionation on Sephadex G-50 medium and G-50 fine eluted with alkaline buffer and final fractionation on G-50 superfine in 1.0 M acetic acid yielded a pure protein of 13,000 daltons as determined by sodium dodecyl sulfate electrophoresis. The amino acid composition of the protein has been determined and it contains 126 residues with no tryptophan detectable. Tryptic peptide maps demonstrate that the protein does not contain glucagon and RIA of the peptide did not detect any immunoreactive glucagon or gastrin. The isoelectric point is 6.4. The intact protein is resistant to Edman degradation and the partial N-terminal sequences of two CNBr fragments are: Lys-Arg-Leu-Ala-Leu ...., Glu-Gly-Gly-Thr-Val-Val-Val-Asn-Ser.... The C-terminal residue, alanine was determined using carboxypeptidase Y. The isolated peptide, in the range of 10(-15)-10(-9) M stimulated oxyntic cell hydroxyl ion production in sections of guinea pig gastric fundus. The dose response was linear with biphasic peaks at 10(-14) and 10(-9) M and the maximal response to the peptide was equal to that observed with gastrin. The addition of either atropine (10(-5) M) or cimetidine (10(-5) M) with the peptide (10(-14) M) caused greater than 50% inhibition of oxyntic cell stimulation (P less than 0.005). This peptide is a potent stimulator of the oxyntic cell and its effect is inhibited by muscarinic cholinergic and H2 receptor blockers. Hence, it represents a significant component of the physiological enterooxyntin effect observed in response to intestinal meals.

Action of gastrin in guinea pig oxyntic cells. Studies using quantitative cytochemistry.

The mechanism of action of gastrin was investigated using cytochemical quantitation of hydroxyl ion production (HIP) in guinea pig gastric oxyntic mucosa. The reaction depends upon the trapping of OH ions produced during gastric stimulation and is blocked by the benzimidazole, Hassle 149/94, which inhibits the K+ + H+-ATPase and by acetazolamide, an inhibitor of carbonic anhydrase activity. It is thus a measure of hydroxyl ions produced during stimulation of the oxyntic cell and reflects upon hydrogen ion production. Gastrin (2.5 X 10(-16) -2.5 X 10(-12) M) caused a linear dose-dependent stimulation of HIP in the oxyntic cells. The response was biphasic, with an early peak at 90 s and a secondary rise at 240 s, which persisted for 10 min. Natural human gastrin (sulfated and nonsulfated) and the active COOH-terminal octapeptide fragment of gastrin stimulated HIP, whereas the biologically inert NH2-terminal (1-13) fragment of gastrin had no effect. The activation of oxyntic cell HIP by gastrin was neutralized by an antiserum directed towards the COOH-terminus of gastrin and not by nonimmune serum. Cimetidine (10(-5) M) blocked 25% and atropine (10(-5) M) had no effect on gastrin-stimulated HIP. EGTA (10(-3) M) and LaCl3 (10(-3) M) inhibited the action of gastrin by 67 and 52%, respectively. The calmodulin antagonists, trifluoperazine (10(-5) M), pimozide (10(-5) M), and the naphthalene sulfonamides, W-7 and W-13 (10(-5) M), inhibited gastrin-stimulated HIP by 45.6 38.5, 42.3, and 37.2%, respectively. Higher doses of W-7 and W-13 (10(-4) M) inhibited gastrin-stimulated HIP by 83 and 67%. The Ca2+ ionophore, A23187 (10(-4) M), stimulated HIP. Thus, it appears that gastrin stimulation of HIP is complex. 25% of its action is via a histamine-dependent pathway. 45% of its action is dependent upon extracellular Ca2+. Its action is also in part dependent upon a Ca2+/calmodulin mechanism.

Role of calcium and calmodulin in activation of the oxyntic cell by histamine and carbamylcholine in the guinea pig.

The role of calcium in stimulation of the oxyntic cell by histamine and carbamylcholine was studied using a sensitive quantitative cytochemical staining technique that measures oxyntic cell hydroxyl ion production (HIP) as an index of acid secretion. Histamine (10(-17)-10(-14) M), carbamylcholine (10(-12)-10(-9) M), and extracellular calcium (10(-7)-10(-3) M) caused a linear, dose-dependent stimulation of the oxyntic cell. EGTA (10(-6) M) inhibited carbamylcholine by 50% but not histamine-stimulated activity. Lanthanum chloride (10(-6) M) caused 100% inhibition of carbamylcholine-induced activity but did not affect histamine-stimulated activity. A maximally effective dose of calcium (10(-4) M) caused additive effects on HIP at low doses of carbamylcholine without alteration of the maximal effect of carbamylcholine. Calcium (10(-4) M) did not enhance the effects of histamine. The calmodulin antagonists, trifluoperazine (10(-5) M), pimozide (10(-5) M), and a naphthalenesulfonamide (W-7), inhibited the integrated response to histamine by 54, 56, and 53%, and that of carbamylcholine by 65, 64, and 99%, respectively. Thus, extracellular calcium per se, stimulates the oxyntic cell. The action of carbamylcholine is completely dependent upon calcium/calmodulin mediation, supporting the concept that cholinergic actions are mediated via calcium-calmodulin events. Although histamine does not require extracellular or membrane calcium events to stimulate the oxyntic cell, calmodulin appears to participate in histamine action.

Enterooxyntin release from isolated perfused canine jejunum

A humoral factor may mediate the intestinal phase of gastric acid secretion. An ex vivo perfused segment of canine jejunum maintained by an oxygenated asanguinous physiologic perfusate was used to test for release of an enterooxyntin (EO) in response to balloon distention at 30 mm Hg for 15 min. Gastric acid secretion in guinea pig fundic mucosa was determined indirectly by a quantitative cytochemical bioassay (CBA) of oxyntic cell hydroxyl ion production (HIP). An increase in the optical density (OD) caused by the cytochemical stain in the oxyntic cells reflects HIP, an index of acid secretion. Basal OD for segments with distention was 16.6 ± 0.53 and for those without 15.5 ± 0.68 (NS). Results are expressed as mean change of OD from basal (mean ΔOD ± SEM). ∗ Time (min) 10 30 60 120 Mean ΔOD, distention 4.9 ± 1.6 ∗ 5.9 ± 1.1 ∗ 7.2 ± 1.2 ∗ 5.2 ± 0.9 ∗ Mean ΔOD, no distention 0.6 ± 1.0 0.1 ± 0.8 0.58 ± 1.0 0.7 ± 1.2 ∗ Significant stimulation of HIP ( P < 0.02) by EO. EO caused greater stimulation of HIP than gastrin or histamine. EO was heat stable. Trichloroacetic acid treatment decreased EO activity as did pronase digestion suggesting that EO is composed of one or more peptides. Conclusion: EO, an acid secretagogue, is a humoral agent probably composed of one or more peptides and is released by small bowel distention. Mechanical distention of the small bowel may be an important mechanism for the perpetuation of gastric acid secretion. The ex vivo perfused jejunal segment in conjunction with the CBA are ideal tools with which to study mechanisms of release of EO and the mechanism of action of EO on the oxyntic cell.

Cathodic Oxygen Consumption and Electrically Induced Osteogenesis

Small amounts of electric current stimulate bone formation in the region of a cathode. The purpose of this experiment is to compare changes in oxygen and hydroxyl ion concentration that occur at the cathode at current levels known to be capable of inducing osteogenesis (10-20 muamps) with those changes that occur at current levels known to be toxic to bone (100 muamps). An oxygen consumption chamber containing an oxygen electrode is fitted with two stainless steel electrodes which are connected to a constant current source. At the cathode, with a current of 100 muamps, oxygen is consumed at nearly stoichiometric rates. At higher current (100 muamps) levels, cathodic oxygen consumption gives way to hydrogen evolution. Cathodic hydroxyl ion production is directly proportional to current. It is concluded from these in vitro experiments that at 10-20 muamps the oxygen tension in the vicinity of the cathode is lowered and the pH is moderately increased. At 100 muamps the oxygen tension is not lowered, but the pH is increased dramatically. If these same changes occur in the vicinity of a cathode in vivo, then lowering the local tissue oxygen tension and raising the local pH may be mechanisms operative in electrically induced bone formation.

The effect of changes in lactate uptake on the intracellular pH of the perfused rat liver.

1. Mean intracellular pH (pHi) and lactate have been measured simultaneously in the isolated perfused rat liver on two successive occasions separated by an interval of 20 min. In some experiments extra lactate was added to the perfusion medium immediately after the first measurement of pHi. 2. There was a direct relationship between the change in pHi over this interval and the simultaneous change of lactate uptake. 3. This finding is consistent with the hypothesis that lactate enters the liver cell at least partly in the ionized form and that its metabolism is accompanied by the effective production of hydroxyl ions. 4. These observations are discussed in terms of a possible control mechanism for lactate uptake by the liver.

Energy-linked Changes of Hydrogen Ion Concentration in Submitochondrial Particles

Abstract 1. Submitochondrial particles supplemented with bromthymol blue, found in independent experiments to be bound to the particles, exhibit characteristic decreases of absorbance upon activation of electron transport by addition of substrate or oxygen to the anaerobic material or by addition of adenosine 5'-triphosphate to the sulfide-inhibited material. The responses are reversible upon exhaustion of substrate or oxygen or upon utilization of adenosine 5'-triphosphate. 2. Inhibitors of electron transport (sulfide or antimycin A) reverse the bromthymol blue responses activated by substrate and oxygen. 3. Uncoupling agents, for example, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, rapidly reverse the bromthymol blue responses upon addition of substrate, oxygen, or adenosine 5'-triphosphate. 4. Glass electrode measurements external to the submitochondrial particles confirm an alkalinization outside the particles on activation of electron transport. On the basis of these observations, the decolorization of bromthymol blue upon activation of electron transport is attributed to an intravesicular acidification. 5. The total amount of hydroxyl ion production exterior to the vesicles is 50 to 60 mµmoles of hydroxyl ions per mg of protein, a value roughly 10 times in excess of the maximal content of respiratory carriers of the particles, and several fold greater than the measured calcium content, but considerably less than the magnesium content. 6. In view of the observed cation content of the submitochondrial particles employed and the similarities in the bromthymol blue responses caused by activation of electron transport to those caused by the addition of acetate or ethylene glycol 2-(2-aminoethyl)-tetraacetate, the intravesicular acidification is attributed to the energy-linked movement of bound cations from the inside of the vesicle to the outside medium. 7. The response of bromthymol blue affords a highly sensitive measure of energy conservation; a response to the oxidation of 1 nmole of reduced β-diphosphopyridine nucleotide is readily measurable. 8. The kinetics of activation of the bromthymol blue response and of its inactivation by inhibitors of electron transport and by uncouplers as well suggests that the cation movement is a reversible phenomenon and that a circulation of cations through the vesicular membrane occurs. 9. Much experimental evidence is consistent with a chemical mechanism for cation movements below 0.2 mg of protein per ml, suggesting that the bromthymol blue response is due to a dissociable component of the vesicular membranes, presumably a cation such as calcium. Also, ethylene glycol 2-(2-aminoethyl)-tetraacetic acid and acetate give bromthymol blue responses similar to those induced by activation of electron transport or adenosine 5'-triphosphate. The slow initial rate of hydrogen ion formation is consistent with the chemical mechanism. 10. The data of this paper do not afford support for compulsory movements of electrons in the respiratory chain and of hydrogen ions through the vesicular membrane. The initial rate of hydrogen ion formation is over 1000-fold slower than the initial rate of oxidation of reduced quinone and flavoprotein. The magnitude of the hydrogen ion change is too small by a factor of about 10 to represent a jump due to the oxidation of reduced quinones and flavin. The collapse of the pH gradient across the vesicular membrane occurs nearly as rapidly upon inhibition of electron transport by antimycin A as it does upon addition of an uncoupling agent. 11. A structural model for the movement of cations in a circulating pathway through the vesicular membrane operating according to the chemical mechanism has been proposed and is consistent with the available experimental data. 12. It is concluded that the chemical mechanism for oxidative phosphorylation is worthy of detailed experimental investigation.

Studies on the ionization produced by metallic salts in flames. IV. The stability of gaseous alkali hydroxides in flames

The electron concentration produced by the addition of alkali metal salts to a wide range of hydrogen/air flames extending to the air-rich side of stoichiometric composition has been measured by the method of attenuation of centimetric radio waves. Considerable deviations from the predicted behaviour on the basis of the known ionization potentials of the metals and the measured temperatures have been observed. The main effect noted is that for two flames of the same temperature, but on opposite sides of stoichiometric composition, the air-rich one always shows a markedly lower attenuation, an effect which is by far the most pronounced in the case of caesium. The electron concentration throughout is considerably below the predicted level. Simple statistical calculations have shown that the formation of gaseous ion pair molecules of the alkali hydroxides by combination with the hydroxyl radicals in the flame is plausible, and an analysis of the electron concentrations on this basis has shown that the results are compatible with removal of a large amount of caesium as hydroxide, but not of potassium and sodium. This agrees with the expected difference in energy of formation of caesium and potassium hydroxides, from the gaseous metal and hydroxyl, of about 5 kcal/mole. It has not proved possible to explain the whole of the deviations of the electron concentration in this way, but by incorporation of a further effect, of production of hydroxyl ions, which is independent of the metal added, a complete resolution may be obtained. The concentrations of hydroxyl ion predicted by the analysis show agreement both with the observed discrepancy with the theoretical electron concentration, and with the order of magnitude of hydroxyl ion concentration obtained earlier by an independent and more direct method (Smith &amp; Sugden 1952). The hydroxyl radical concentrations implied by this analysis show excellent agreement with those obtained from thermodynamic calculation of the burned gas composition at equilibrium. Values for the heat of formation of gaseous potassium hydroxide and gaseous caesium hydroxide, from the gaseous metal and hydroxyl, which the data require are 87.5 ± 3 and 92.5 ± 3 kcal/mole respectively. The analysis of the results further implies an electron affinity for gaseous OH of 69 ± 5 kcal/mole, which agrees reasonably with the value obtained previously from flame measurements of 62 ± 6 kcal/mole.