Diluted hydrogen

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Better results are obtained by transferring 25.0 mL of the diluted hydrogen peroxide solution to a conical flask, and adding 100 mL 1M(1 20) sulphuric acid. Pass a slow stream of carbon dioxide or nitrogen through the flask, add 10 mL of 10 per cent potassium iodide solution, followed by three drops of 3 per cent ammonium molybdate solution. Titrate the liberated iodine immediately with standard 0.1M sodium thiosulphate in the usual way. 

Some of the polymeric membranes are suitable for bulk separation of hydrogen from impurities to enrich a dilute hydrogen stream. Dense polymers permeate gases by solution diffusion mechanism. The permeation rate of a gas species through a polymer membrane... 

Estimates of diffusive leakage using the same geometry used for pressure-driven leakage, and the diffusivity values in Table 5.1 show leak rates of 0.04 sccm/cm2 for pure hydrogen, or 0.008 sccm/cm2 for reformate or nitrogen diluted hydrogen streams. Thus, diffusive leak rates of 2 to 10 times that of hydrodynamic may be expected. 

Barlow, R. S., N. S. A. Smith, J.-Y. Chen, and R. W. Bilger (1999). Nitric oxide formation in dilute hydrogen jet flames Isolation of the effects of radiation and turbulence-chemistry submodels. Combustion and Flame 117, 4—31. 

Draper WM, Crosby DG. 1984. Solar photooxidation of pesticides in dilute hydrogen peroxide. J Agric Food Chem 32 231-237. 

In the Thought Lah above, you may have included the enzyme catalase in your brainstormed list. Catalase in your blood is responsible for the fizzing you see when you use a dilute hydrogen peroxide solution to disinfect a cut. When dilute hydrogen peroxide is poured on a cut, it decomposes to oxygen gas and water. The decomposition reaction is catalyzed by catalase. 

As with the other reactor configurations, vaporizers, heat exchangers, and a heat source are also needed for microreactors.Unless the hydrogen is 99.999% pure, the PEM fuel cell typically will utilize 70—80% of the diluted hydrogen fed to it. The unreacted hydrogen from the fuel cell anode, augmented with additional fuel as needed, can be used as fuel for the combustor. The use of anode off-gas requires special controls for transient operating conditions for example, a mechanism is needed to... 

In natural water, singlet oxygen originating from humic substances has been shown, for example, to oxidize thioether pesticide contaminants such as disulfoton (Zepp et al. 1981). Irradiation of dilute hydrogen peroxide in the presence of various non-sunlight-absorbing herbicides results in enhanced oxidation of these substances (Draper and Crosby 1981). 

Rather unique multicomponent catalysts are those in which one of the components, being volatile, has to be replenished continuously. The oxidation of dilute hydrogen sulfide to elementary sulfur by air with active carbon as a catalyst is such an example. Small amounts of ammonia, if added to the gases entering the reactor, favor and complete this catalytic reaction the ammonia leaves the reactor unchanged (45). 

Titanium in the framework of pentasil zeolites induces oxygenation activity with diluted hydrogen peroxide as oxidant, thus constituting a new catalytic system. 

V/V hydrogen peroxide solution. Dilute dilute hydrogen peroxide solution R in water R in order to obtain a 0.25% V/V solution. 

Other Applications. Metal hydrides are unique in that they are one of the few compounds that selectively and reversibly absorb large quantities of hydrogen at practical temperatures and pressures. This property enables one to treat dilute hydrogen streams that cannot be otherwise economically treated. 

Ten millilitres of 0.25 N hydrochloric acid is added to the residue, which is then boiled under reflux for a few minutes. Materials with high manganese content may yield pink or brown solutions at this stage. If this occurs, dilute hydrogen peroxide solution is added until the colour disappears. The molybdenum contents of the sample are then determined by the iodine catalytic method on the autoanalyser. 

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