Hydrochloric acid diffusion

These common generalizations help to solve only the routine problems with which we are faced. Many problems remain. For example, we may want to know the rate at which hydrochloric acid diffuses into oil-bearing sandstone. We may need to estimate the drying speed of lacquer. We may seek the rate of flavor release from lemon pie filling. All these examples depend on diffusion none can be accurately estimated with the common generalizations. 

Jamieson and McNeill [142] studied the degradation of poIy(vinyI acetate) and poly(vinyI chloride) and compared it with the degradation of PVC/PVAc blend. For the unmixed situation, hydrogen chloride evolution from PVC started at a lower temperature and a faster rate than acetic acid from PVAc. For the blend, acetic acid production began concurrently with dehydrochlorination. But the dehydrochlorination rate maximum occurred earlier than in the previous case indicating that both polymers were destabilized. This is a direct proof of the intermolecular nature of the destabilizing effect of acetate groups on chlorine atoms in PVC. The effects observed by Jamieson and McNeill were explained in terms of acid catalysis. Hydrochloric acid produced in the PVC phase diffused into the PVAc phase to catalyze the loss of acetic acid and vice-versa. 

Both anodic and general inhibitors are nonpassivating and are suitable for use with hydrochloric acid-based cleaners. Other inhibitor groups include filming amines such as polymethylimine and diamines, the rosin-amine ketones, and also some of the imidazoline surfactants. The imidazolines provide increased protection at levels up to their critical miscelle concentration (CMC), above which there is a leveling off as a thick, adherent diffusion barrier is formed. 

One difficulty in Equation 6 lies in the determination of the diffusivity constant for highly concentrated acids over a broad range of temperature. However, available data (13), combined with viscosity values of hydrochloric acid, lead to estimates shown in Tables I and II for the field cases that will be described later on. 

The metal content analysis of the samples was effected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES Varian Liberty II Instrument) after microwaves assisted mineralisation in hydrofluoric/hydrochloric acid mixture. Ultraviolet and visible diffuse reflectance spectroscopy (UV-Vis DRS) was carried out in the 200-900 nm range with a Lambda 40 Perkin Elmer spectrophotometer with a BaS04 reflection sphere. HF was used as a reference. Data processing was carried out with Microcal Origin 7.1 software. 

The GDE for hydrochloric acid electrolysis is characterised by micro-scale hydraulic problems connected with the competition between the gas phase (oxygen), which has to diffuse towards the catalyst, and the liquid phase (water), which must be released. This competition is managed basically by a flow-through structure provided with hydrophobic channels of relatively large diameter. These are formed from PTFE (the binder of the structure) and catalyst particles and account for regulating the gas phase. Hydrophilic channels with smaller diameters (one order of magnitude smaller), which are located in the micro-porous carbon particles of the catalyst support (e.g. Vulcan XC-72), act as water absorbers. A consequence of the electrolysis process is that the catalyst itself is partially covered by liquid. This reduces its effectiveness and accounts for extra voltage. 

In a 0.5 M KCl solution to which is added hydrochloric acid until pH 2, TcO gives three diffusion-controlled waves with half-wave potentials of —0.14,... 

Figure 2. Conductivity diffusion coefficient (mobility) of protons and water self-diffusion coefficient of aqueous solutions of hydrochloric acid (HCl), as a function of acid concentration (molarity, M) (data are taken from ref 141).

B. 2-Naphthalenethiol. In a 250-ml. flask, fitted with a diffusion tube2 and swept with nitrogen, is placed 23.1 g. (0.10 mole) of O-2-naphthyldimethylthiocarbamate (Note 4). The flask is heated at 270-275° for 45 minutes in a salt bath (Note 5). After cooling, a solution of 8.4 g. (0.15 mole) of potassium hydroxide in 10 ml. of water and 75 ml. of ethylene glycol is added to the flask. The diffusion tube is replaced by a condenser, and the mixture is heated at reflux for 1 hour (Note 6). The cooled reaction mixture is poured onto 150 g. of ice. After the ice has melted, the mixture is shaken two times with 150-ml. portions of chloroform. The chloroform layers are discarded, and the aqueous layer is cautiously acidified with concentrated hydrochloric acid (Note 7) and shaken three times with 75-ml. portions of chloroform. The organic layers are combined and dried by filtration through anhydrous magnesium sulfate. The solvent is removed by distillation to yield 13-15 g. of crude product. Distillation yields 10.3-12.8 g. (71-80%) of pure 2-naphthalenethiol, b.p. 92-94° (0.4 mm.), m.p. 80-81° (Note 8). 

Under suitable conditions, certain chemical reactions will give rise to nacreous sulphur the most satisfactory result is obtained by allowing slow inter-diffusion of solutions of sodium thiosulphate and potassium hydrogen sulphate to occur.7 Another method involves the gradual decomposition of sulphur chloride or bromide by the vapour of water or methyl alcohol at the ordinary temperature.8 The decomposition of calcium polysulphidcs by hydrochloric acid,9 and of hydrogen persulphide by the addition of alcohol, ether, ethyl acetate or other organic solvents, also yields sulphur of the desired modification. 

Hydrochloric acid Acidic 1.18 Diffusion and formation of reaction products... 

Specific chemical interaction between the chloride ion and metal ions present at the pore surfaces has also been considered as a possible factor contributing to retardation of HC1 diffusion. To evaluate this possibility, one portion of the coconut carbon was washed with acetic acid to reduce its ash content from 0.7% to 0.6%, and another portion with hydrochloric acid to reduce its ash content from 0.7% to 0.3%. The finite bath technique was used to study these two carbons in otherwise identical systems consisting of 10 -M NaCl, 1.5 grams carbon per liter, an initial pH of 3.50 (HC1), at a temperature of 25 °C. The corresponding isotherms show no significant difference between these carbons and the... 

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