External acidity

Kiel, O.M. "Fracturing Using Acid External Emulsions," US Patent 3,799,266(1974). 

Fig. 3 represents the IR spectra in the hydroxyl region and in the OH bending region for the activated 4A and 5A zeolite samples. The outgassed 5A 86 sample IR spectrum exhibits a weak absorption at 3744 cm 1 which corresponds to non acidic external silanol groups and a large contribution between 3700 cm 1 and 3500 cm 1 (Fig. 3a). This... 

Fig. 3.74 Sulfuric acid external dynamic rinsing simulation...

Dat/rolevri-tartaric acid, racemic tartaric acid (externally compensated optically inactive can beresolved into d and / components),... 

A suspension of 27.5 g. (0.20 mole) of the crude nitroso compound in 200 ml. of a mixture of 1 part of concentrated nitric acid to 3 parts of water is agitated and cooled over a period of 3 hours. The solid is filtered off, washed with water, and dissolved in 5 sodium hydroxide solution. The alkaline solution is heated with activated carbon, the resulting mixture filtered, and the filtrate treated with excess lO o hydrochloric acid by dropwise addition of the acid. External cooling is used during the acidification. The 2-methyl-4-nitro-phenol is precipitated in an overall yield of 82. The product melts at 91°. 

Acidity, external surface 13-P-09 Adsorption isotherms, modelling 16-P-lO... 

Actions and Uses.—Internally —Antacid in indiges tion, chronic diarrhoea and dysentery antidote to oxalic and most other acids. Externally — Desiccant for absorbing irritating discharges for protecting wounds, bums, and scalds from the air also in erysipelas. 

Actions and Uses.—Internally —Similar to, but more certain in its action and less liable to produce local irritation than, arsenious acid. Externally —In obstinate skin affections, and for the destruction of pediculi, acari, and other external parasites. ... 

The employment of foamed acid and acid-external emulsions (oil as the dispersed phase and gelled acid as the continuous phase) are other methods used to control the loss of acid solutions. The disadvantage of using oils is that a large concentration of oil is required to increase the viscosity of the emulsion formulation, which reduces the acid concentration and, therefore, the amount of acid available for fracture etching. Foaming the acid also reduces the amount of acid available for etching since less acid is present per unit volume injected. 

Figure 1 NMR spectrum of a guinea-pig heart perfused with Krebs-Henseleit solution. The spectrum was acquired at 8.7 T using a broad-band probe tuned to 145.8 MHz. Peak assignments are 1, phenylphosphonic acid (external reference) 2, phosphomonoesters 3, inorganic phosphate (P ) 4, phosphocre-atine (PCr) 5, y-phosphorus of adenosine triphosphate (ATP) 6, a-phosphorus of ATP 7, 5-phosphorus of ATP. The spectrum was acquired in 2.5 min by summing 72 free induction decays (FIDs) with a 35 gs pulse and a repetition time of 2 s. Prior to Fourier transformation the FID was subjected to exponential multiplication with a 20 Hz line broadening factor.

The system that provides deepest penetration is an oil-external emulsified add. Add-oil emulsions can be oil eoctemal or acid external. Oil-external emulsions have higher dissolving capacity per unit volume and are generally more effective. A common emulsion mixture is 70% acid-30% oil. A limitation is that emulsified add can be difficult to pump at suffident rate in deeper wells because of high friction pressure during injection. Gelled acids provide the most friction reduction. The temperature limit of an emulsified acid is about 300°F, because of the associated well depth. 

Emulsitied acid systems are interchangeable with gelled acid acid emulsions can be either oil external or acid external. 

---