Evolution gradualism

Jorne et al. [36] investigated the reactivity of graphites in acidic solutions that are typically used for Zn/Cl2 cells. The degradation of porous graphite is attributed to oxidation to C02. The rate of C02 evolution gradually decreased with oxidation time until a steady state was reached. The decline in the C02 evolution rate is attributed to the formation of surface oxides on the active sites. 

In the vesicle suspension of Fig. 8 it was possible to isolate the centers for dihydrogen and dioxygen evolution and thus to avoid cross reactions of S+ and A- with the catalysts for H2 and 02 evolution, respectively. However, it turned out that 02 evolution gradually inhibits the H2 evolution, because oxygen evolved in the outer volume permeates across the membranes and destroys the apparatus for dihydrogen evolution located inside the vesicles. Note, that such a problem also arises for biological systems adapted to provide simultaneous evolution of H2 and Oz [275, 276],... 

Beta-Ga203 calcined at 1073 K showed good photocatalytic activity for the reduction of CO. The rate of CO evolution gradually increased with photoirradiation time. After photoirradiation for 48 h, 10.96 pmol of CO gas had evolved over Ga Oj and the conversion rate of CO was 7.3%, as shown in Figure 12.3. The amount of CO chemisorbed on Ga Oj became saturated at a concentration of 9.1 mol g-Ga Oj" and an equilibrium pressure of ca. 2.5 kPa. The amount of CO chemisorbed on Ga Oj was smaller than that on MgO or ZrO. Furthermore, the amount of CO gas evolved in the photocatalytic conversion of CO, in the presence of H, increased... 

Add 15 g. of finely powdered ammonium carbonate gradually to 50 ml. of glacial acetic acid contained in a 150 ml. round-bottomed flask, shaking the mixture during the addition to ensure a steady evolution of carbon dioxide. When all the carbonate has... 

Proceed as follows for both solid and liquid compounds. By means of a test-tube holder, hold the tube in a horizontal position, and by means of a small flame gently heat the mixture at the open end. Increase the size of the flame gradually until the mixture is red-hot at this end. Now slowly and cautiously extend the heating towards the closed end until the whole of the mixture is red-hot. (If during the extension of the heating, the mixture tends to be pushed out of the tube by the evolution of gas, stop the heating momentarily, and rotate the... 

Mix 100 g. of ammonium chloride and 266 g. of paraformaldehyde in a 1-litre rovmd-bottomed flask fitted with a long reflux condenser containing a wide inner tube (ca. 2 cm. diameter) the last-named is to avoid clogging the condenser by paraformaldehyde which may sublime. Immerse the flask in an oil bath and gradually raise the temperature. The mixture at the bottom of the flask liquefies between 85° and 105° and a vigorous evolution of carbon dioxide commences at once remove the burner beneath the oil bath and if the reaction becomes too violent remove... 

In a 1 or 1-5 htre round-bottomed flask prepare a solution of 53-5 g. of o-toluidine in 170 ml. of 48 per cent, hydrobromic acid, cool to 5° by immersion in a bath of ice and salt. Diazotise by the gradual addition of a solution of 36 -5 g. of sodium nitrite in 50 ml. of water stopper the flask after each addition and shake until all red fumes are absorbed. Keep the temperature between 5° and 10°. When the diazotisation is complete, add 2 g. of copper powder or copper bronze, attach a reflux condenser to the flask, and heat very cautiously on a water bath. Immediately evolution of gas occurs, cool the flask in crushed ice unless the... 

Evolution of ammonia from a boiling dilute solution of diammonium phosphate gradually reduces the pH. This process is used commercially to control the precipitation of alkaH-soluble—acid-insoluble coUoidal dyes on wool. Other ammonium orthophosphate salts of interest are ammonium hemiphosphate [28537-48-6] NH4H2PO4 H3PO4, and its hydrate [28037-74-3], as well as the trihydrate [78436-07-4] of DAP. 

Handling and Storage. Cyanamide solution dimerizes to dicyandiamide and urea with the evolution of heat and a gradual increase in alkalinity accelerating the reaction. Storage above 30°C without pH stabilizer leads to excessive dimerization and can result in violent exothermic polymerization. Cyanamide should be stored under refrigeration and the pH tested periodically. Stabilized cyanamide can be kept at ambient temperature for a few weeks. 

In the past the successful operation of batch processes depended mainly on the skill and accumulated experience of the operator. This operating experience was difficult to codify in a form that enabled full use to be made of it in developing new designs. The gradual evolution of better instmmentation, followed by the installation of sequence control systems, has enabled much more process data to be recorded, permitting maintenance of process variations within the minimum possible limits. 

Three hundred and forty-five grams (1.7 moles) of ethyl ethoxalylpropionate, b.p., ii4-ii6°/io mm. (p. 54), is placed in a round-bottomed flask, of suitable size carrying a reflux condenser, and a thermometer is suspended from the top of the condenser into the liquid. The ethyl ethoxalylpropionate is then heated until a Aigorous evolution of carbon monoxide begins (130-150 ). The temperature of the liquid is gradually raised as the gas evolution diminishes, and finally the liquid is refluxed until no more gas comes off. The ethyl methylmalonate is then distilled. It boils at ig4-iq6 /745 mm., and the yield is 288 g. (97 per cent of the theoretical amount). 

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