Cent Hydrochloric Acid Research Articles

Exploration of Encapsulated Modified Psyllium Husk for Preparation of Probiotic Basundi

Background: The dairy industry is one of the largest industries in India. The exports were made to 105 countries in the world. Dairy production is one of the major sustenance factors for the rural economy of India. Notably, India ranks first in Isabgol production (98%) and is the sole supplier of seeds and husk in the international market. Among medicinal plants, Isabgol is the first ranked foreign exchange earner for the country. India is the largest producer and the main supplier of seed and husk to the world market. It contains a significant number of proteins and husk yields colloidal mucilage which are valued for medicinal application and is used in Ayurveda, unani and allopathic systems of medicines. It is the main constituent of a number of laxative preparations. The psyllium is high in soluble fibre content with detoxing effect over digestive system makes it a very apt nutraceutical. Basundi is one of the heats desiccated indigenous products popular in Western part of India, mostly Maharashtra and Gujarat. It can be classified in the condensed milk group along with rabri, khoa, mithai and kheer and can be considered similar to sweetened condensed whole milk. Methods: The present investigation indicates utilization of encapsulated lactic acid bacteria culture (Lactobacillus acidophilus, Lactobacillus bulgaricus) and modified psyllium husk for the preparation of probiotic basundi. The prepared probiotic basundi was analyzed for sensorial, physicochemical and microbial quality parameters. Probiotic basundi was prepared from 1000 ml of milk, 90 gm sugar, 02-03 pieces of cardamom, saffron and encapsulated LAB culture having (107, 108 and 109 cfu/gm containing equal proportions of Lactobacillus acidophilus and Lactobacillus bulgaricus) with 0.65 per cent hydrochloric acid modified psyllium husk. The probiotic basundi was then stored at refrigerated conditions at 4°C for 08 hrs. Result: The organoleptic evaluation of probiotic basundi was carried out. As per the score of hedonic scale, basundi with encapsulated 10 per cent probiotic culture (109 cfu/gm) with 0.65 per cent hydrochloric acid modified psyllium husk had shown maximum consumer acceptability (8.3) among all samples.

Corrosion and inhibition of N80 steel in 5% HCl solution by SA1-3

PurposeThis paper aims to describe the corrosion behavior and possibility of inhibition by corrosion inhibitor SA1-3 in acidizing solution (5 per cent hydrochloric acid [HCl] solution). The study aims to explain the mechanism of corrosion and inhibition of N80 steel in 5 per cent HCl solution to provide theoretical basis for expanding the range of application of N80 steel in acidification process.Design/methodology/approachThis paper opted for a laboratory study using simulation of acidizing solution to do the experiments. The results of experiments including weight-loss method, electrochemical method and surface analysis were used to explain the mechanism of corrosion and inhibition so as to predict the dissolution progress of N80 steel in 5 per cent HCl solution with and without inhibitor SA1-3.FindingsThis paper provides theoretical insights about how to inhibit the corrosion behavior of N80 steel in 5 per cent HCl solution. It suggests that the corrosion inhibitor which can form a protective film on the steel surface should be used to expand the application of N80 steel in acidizing solution. The inhibitor SA1-3 is a kind of cathodic corrosion-controlling inhibitor which mainly inhibits cathode corrosion; it cannot change the corrosion mechanism of N80 steel.Originality/valueThis paper provides a theoretical basis for the corrosion behavior and inhibition mechanism of N80 steel in acidizing solution.

A Mannich base 1-phenyl-3-(1-pyrrolidinyl)-1-propanone: synthesis and performance study on corrosion inhibition for N80 steel in 15% hydrochloric acid

Purpose – The purpose of this paper is to set out a study of a Mannich base, which was synthesized and used as an acidizing corrosion inhibitor first, and to the corrosion inhibitor mechanism. Design/methodology/approach – A Mannich base, 1-phenyl-3-(1-pyrrolidinyl)-propanone (PHPP), was synthesized with acetophenone, pyrrolidine and formaldehyde at pH = approximately 2-3. The structure of PHPP was characterized by elemental analysis and Fourier transform infrared spectroscopy (FTIR). The corrosion inhibition of PHPP on N80 steel in 15 per cent hydrochloric acid (HCl) was studied by weight loss method, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX), and the adsorption behavior of PHPP on the surface of N80 steel was discussed. Findings – The results showed that the inhibition efficiency reached to 99.8 per cent and corrosion rate was 2.65 g·m-2·h-1 at 0.6 per cent of PHPP concentration in 15 per cent HCl, which indicated that PHPP presented excellent corrosion inhibition performance. The results of SEM and EDAX analysis showed that PHPP could be absorbed on the surface of N80 steel. The adsorption process of PHPP on the surface of N80 steel was chemisorption. This process was spontaneous and obeyed Langmuir adsorption isotherm. Originality/value – It was found that PHPP presented excellent corrosion inhibition performance, and it is practicable to enhance oil production in oilfield development as a oil-well acidizing inhibitor. The study results can provide theoretical guidelines for the development of the inhibitor.

Comparison study on the effect of acid and nitrate salt on the properties of poly(vinyl alcohol) coating doped with dye consist of anthocyanin

Purpose – The purpose of this paper is to observe the thermal and colour stabilities of coating films consisting of natural dye anthocyanin colourant with acid and nitrate salt as additives. Design/methodology/approach – The natural dye was extracted from Hibiscus sabdariffa L. (Roselle) by using distilled water as solvent. The extracted dye was mixed with 1 weight per cent hydrochloric acid and 5 weight per cent calcium nitrate to conduct the comparison study. The dye samples were than mixed with poly (vinyl alcohol) (PVA). The mixtures were applied on glass panels to form coating films. The coating films were left to dry for 24 hours. The thermal stability of coating films was investigated by using thermogravimetric analysis (TGA). The amorphousness coating films molecular structures were observed by using x-ray diffraction (XRD). CIE L*a*b* colour coordinate space technique was used to investigate the coating films colour stability against ultraviolet (UV). Findings – The results show that addition of hydrochloric acid (HCl acid) enhanced thermal stability of PVA-anthocyanin coating and shifted the degradation temperature to higher temperature at 300°C. HCl acid also improved UV stability of the coating system significantly with the reduced ΔE from 26.67 to 16.89. Addition of calcium nitrate (Ca(NO3)2) salt promotes good interaction with PVA-anthocyanin system that caused structural changes, improved thermal stability and increased Tg from 61.5 to 83.1°C. Research limitations/implications – The potential of using natural dye extracted from plant as renewable material. Practical implications – The coating films developed in this works are suitable for glass substrate application. Originality/value – Development of water-based coating from PVA binder with anthocyanin colourant is introduced in this study.

Thermal and UV degradation of roselle anthocyanin extract and its mixtures with poly(vinyl alcohol) in different acid

Purpose – The purpose of this paper is to observe the colour and thermal stability of natural red dye consisting of anthocyanin with addition of different aqueous acids and applied as coating films. Design/methodology/approach – The natural red dye was extracted from Hibiscus sabdariffa L. (roselle) flowers and mixed with 1 per cent hydrochloric acid, 5 per cent acetic acid, 5 per cent citric acid and 5 per cent oxalic acid. All the dye samples were exposed to heat and UV-B to observe the colour stability by calculating the half-life and rate of reaction. In coating film application, each of the dye samples was mixed with 25 wt% of poly(vinyl alcohol) (PVA) and applied on to a glass substrate. The coating samples’ colour stability was observed by using CIE L*a*b* colour space coordinates. The coating films’ weight loss stability against temperature was observed by using thermogravimetric analysis. Findings – Addition of hydrochloric acid enhances the thermal and UV stability of the anthocyanin natural dye. This can be observed from the calculation of the half-life of the dye. The half-life values for the thermal and UV stability studies were 1,155 hours and 210 hours, respectively. In coating films, the sample with addition of acetic acid showed the highest colour stability with colour difference (ΔE*) value 8.95. Research limitations/implications – The coating films developed in this work are not suitable to be applied on metal substrates due to the presence of water, which can contribute to the corrosion formation. Practical implications – The coating films developed in this work are suitable for washable coating application. In other words, they are non-permanent coatings applied on a glass substrate. Originality/value – Development of water-based coatings from PVA binder with anthocyanin colourant is introduced in this study.

Studies on synthesized nontoxic corrosion inhibitors for N80 steel in hydrochloric acid

Purpose – The purpose of this investigation was to evaluate the protective ability of 2-amino-N-octadecylacetamide (AOA) and 2-amino-N-octadecyl-3-(4-hydroxyphenyl) propionamide (AOHP) as corrosion inhibitors for N80 steel in 15 per cent hydrochloric acid (HCl), which may find application as eco-friendly corrosion inhibitors in acidizing processes in the petroleum industry. Due to scale plugging in the well bore, there can be a decline in the crude production rate, and an acidization operation has to be carried out, normally by using 15 per cent HCl to remove the scale plugging. To reduce the aggressive attack of HCl on tubing and casing materials (N80 steel), inhibitors are added to the acid solution during the acidifying process. Design/methodology/approach – Different concentrations of the synthesized inhibitors AOA and AOHP were added to the test solution (15 per cent HCl), and the corrosion inhibition efficiencies of these inhibitors for N80 steel were calculated from weight loss determinations, potentiodynamic polarization scans and alternating current (AC) impedance measurements. The influence of temperature (298-323 K) on the inhibition behavior was studied. Surface examinations were performed by means of Fourier transform infrared spectra and scanning electron microscope. Findings – AOA and AOHP at 150-ppm concentration showed a maximum efficiency of 90.04 and 94.97 per cent, respectively, at 298 K in 15 per cent HCl solution. Both the inhibitors acted as mixed corrosion inhibitors. The adsorption of the corrosion inhibitors at the surface of the N80 steel was the underlying mechanism of corrosion inhibition. Originality/value – This paper reports the preliminary laboratory results of inhibitors AOA and AOHP for the corrosion prevention of N80 steel casings and tubulars exposed to HCl and may be of practical help to petroleum engineers for carrying out acidization in oil wells after further investigation of the compound at higher temperature.

Corrosion protection of N80 steel in HCl by condensation products of aniline and phenol

PurposeThe purpose of this paper is to evaluate the protective ability of mixtures of aniline and phenol as corrosion inhibitors for N80 steel in 15 per cent hydrochloric acid, which may find application as corrosion inhibitors in acidization jobs in the petroleum industry. Owing to scale plugging at well bore there will be a decline in the crude production and acidization operation has to be carried out in the oil wells, normally by using 15 per cent hydrochloric acid to remove the scale plugging and enhance crude production. If the acid alone is poured in the oil wells through tubular and casing, corrosion of the metal (N80 steel) structures takes place for which an inhibitor is also is used along with the acid.Design/methodology/approachDifferent concentration ratios of the inhibitor mixtures of aniline and phenol were added to the test solution (15 per cent HCl) and corrosion inhibition of N80 steel in hydrochloric acid medium containing the inhibitor additives was tested by weight loss and potentiodynamic polarization measurements. Influence of temperature (ambient temperature to 333 K) and exposure period (6‐24 h) on the inhibition behaviour was also studied. Corrosion products on the metal surface were analyzed by fourier transform infrared (FTIR) and a possible mechanism of inhibition by the compounds is suggested.FindingsProvides information about the protective ability of inhibitor mixtures containing aniline and phenol against corrosion of N80 casing steel in 15 per cent HCl medium. The results in the present study have shown synergistic effect of all the formulations tested. The formulation of the mixture containing 0.1 per cent AL with 0.7 per cent PH has shown a maximum efficiency (75 per cent at ambient temperature) among other tested combinations in the acid medium. The inhibition efficiency exhibited by the inhibitor mixture (0.1 per cent AL with 0.7 per cent PH) in 15 per cent HCl medium at 333 K and after 24 h – test was found to be 43 and 31 per cent, respectively. The inhibitors, in appropriate combinations may find some usefulness at still higher temperatures. Electrochemical measurements indicate that the additives are active towards both sides, i.e. cathodic and anodic. FTIR results of the inhibition product film (formed on the metal surface after the corrosion test) reveal the presence of the inhibitor molecules in the surface film on the metal. Aniline and phenol molecules of the inhibitor mixture undergo condensation after their addition to the acid solution and may result in formation of protective surface film on the metal consisting of diphenylamine (as also revealed by FTIR spectroscopy) which may also contribute to the corrosion inhibition apart from the inhibition offered by aniline and phenol separately.Research limitations/implicationsNormal temperatures of oil wells will be about 363 K. The results presented in this paper refer to temperatures up to 333 K, which perhaps limits its usefulness in actual field conditions. However, further research work to test the inhibition potentiality of the compounds at higher temperatures (363 K and above) is in progress, and will be communicated at a later stage.Practical implicationsThe tested inhibitor mixtures containing aniline and phenol exhibited synergistic effect and a significant inhibition (75 per cent) at ambient temperature that also shows good inhibitive properties after longer exposure period (24 h) and higher temperature (333 K). Appropriate formulations of the compounds may also be effective at still higher temperatures and that may be worked out for possible application in oil wells as corrosion inhibitors for acidization job.Originality/valueThis paper offers preliminary laboratory results of some inhibitor formulations on corrosion prevention of N80 steel casing and tubular in hydrochloric acid that may be of practical help to petroleum engineers for carrying out acidization jobs in oil wells after further investigations of the compounds at higher temperatures and actual field conditions.

Inhibition effect of ethanolamines on oil well tubular material in hydrochloric acid

Acidization is one of the most important techniques to increase the productivity of crude petroleum oil and gas wells. The effective way for protecting these oil well tubular materials is by using corrosion inhibitors during the acidization process. The present study deals with the evaluation of inhibition effect of ethanolamines on oil well tubular materials of grade N‐80 steel in 15 per cent hydrochloric acid at room temperature with 0‐2 per cent amine concentrations. The amines such as mono, di and triethanolamine were studied for their inhibiting capacity by mass loss method, DC polarization method and AC Impedance method. The inhibitor efficiency increases with increasing concentration of amines. Monoethanolamine is found to be more effective than the other two amines.

Studies on corrosion inhibitors for oil‐well tubular material in acid environments

To reduce the corrosion of oil‐ and gas‐well equipment during acid treatment, the acid must be inhibited. The behaviour of N‐80 oilfield material in 15 per cent hydrochloric acid solution inhibited by different inhibitor formulations containing amine, ester and a quaternary ammonium compound was studied at 303K for five hours by the mass loss method. The corrosion rates were obtained by polarisation. Impedance studies were carried out to evaluate the performance of the inhibitor formulations. It was found that the formulation containing 3,000ppm amine, 1,000ppm ester and 1,000ppm quaternary ammonium compound was effective for the specific oil‐well tubular material.

Crosslinked Acid Gel

Abstract A new, stable, crosslinked acid gel has been developed jar fracture acidizing applications. This crosslinked acid can be prepared from acid strengths up to 28 per cent hydrochloric acid. Laboratory tests show the fluid possesses high viscosity and shear stability at temperatures up to 93 °C(200 °F). Viscosity of the acid gel can be reduced in a controlled manner by a chemical additive to aid well cleanup. Rheological data were obtained in a newly designed Viscometer, the pressure rheometer. The rheometer used a bob/cup arrangement to measure the fluid rheology and the fluid was fed to the gap between the bob and cup. A desired pressure was directly applied to the test fluid without using a second pressurizing fluid such as mineral oil or nitrogen. In addition to its viscosity characteristics, the acid reactivity of the crosslinked acid gel with limestone specimens, in a dynamic reaction setup, is drastically retarded. The crosslinked fluid is also residue free in live or spent acid minimizing formation damage. This newly developed fracture acidizing fluid possesses other important fracturing fluid properties such as low friction pressure, good proppant transport characteristics, and good fluid loss control. Results from computer simulation of fracture acidizing treatments indicate deeper penetration is achieved by the cross- linked acid compared to unaltered acid. Field results also show that in several carbonaceous formations, production could be substantially improved if stimulated with this crosslinked acid. Introduction Hydrochloric acid, ranging in strength from 3 to 28% has been used to commercially stimulate carbonate formations since 1932(1). However, the reaction of HC1 (hydrochloric acid) with carbonate rock occurs too rapidly resulting in a limited depth of penetration of live acid into the formation. In order to increase the depth of penetration, acids have been retarded by: adding a suitable gelling agent(2), adding chemical retarders(3), foaming the acid(4), emulsifying the acid(3), or by crosslinking suitable acid gelling agents(5). Each method of retardation has limited use in field application. With the exception of cross-linked acid, each of these methods generate fluids of low viscosity and a low degree of viscous stability (viscosity changing with time) with increasing reservoir temperature. If hydrochloric acid can be crosslinked to generate high viscosity and better viscous stability then not only will it be possible to retard the acid spending but it will also produce longer and wider fractures. Furthermore, crosslinked fluids normally have lower leakoff rate to the formation during pumping than uncrosslinked fluids. This paper presents a newly formulated crosslinked acid gel developed for fracture acidizing. Rheology, acid reaction rate, fluid loss, friction pressure and sand fall data obtained from laboratory studies will be presented. Results obtained from field application of this crosslinked acid will also be presented. The Crosslinked Acid System Crosslinked acid was formulated to be easily mixed on the well site. The system is similar to other commercial crosslinked water-based fracturing fluids commonly used for hydraulic fracturing.

The acid-barium test as an index of intermittent gastro-oesophageal reflux.

The common symptoms of gastro-oesophageal reflux are heartburn and regurgitation and these are often readily recognizable. Reflux is also one of the causes of several other symptoms, e.g. globus pharyngis, chronic laryngitis and pulmonary fibrosis, and the knowledge that reflux is present may be of paramount clinical importance in these conditions. Conventional radiographic tests of reflux during barium meal examinations are unreliable, and pH monitoring and manometric tests are not practicable for routine use. In the acid-barium test, oesophageal peristalsis is observed during perfusion with barium sulphate suspension containing 0·35 per cent hydrochloric acid (pH 1·7). Delayed emptying and non-peristaltic contractions are the indicators of a positive test. The test was done in 350 patients and the results compared with the clinical evidence of reflux. The test correlated only moderately well with the clinical features, mainly because of unexpected positive tests in patients without other evidence of reflux. The reasons for this are discussed, and it is concluded that although the test detects sensitivity of the oesophagus to acid perfusion, a positive test does not necessrily indicate symptomatic reflux. Within limitations the test is of value in concert with clinical and other radiological tests, and because of its simplicity and safety, may be a useful screening test in selecting patients in need of more sophisticated and tedious tests of oesophageal function.

Concerning the composition and source of the acquired enamel pellicle of human teeth

Natural pellicle was collected from sound, clean enamel of extracted, erupted, permanent human teeth. Short-term experimental pellicles were formed in the mouth and from ductal saliva which had been Millipore ®-filtered to remove any contaminating bacteria. Since much of the organic matter from the enamel surface was soluble in the 2 per cent hydrochloric acid used for collection of the pellicles, all the samples analyzed in this study were of “total” pellicle, including both the acid-soluble and the acid-insoluble pellicle. Unfiltered and filtered saliva samples were analyzed for comparison with the pellicles. Total natural pellicle had a fairly constant amino-acid composition which was quite different from the analyses of insoluble pellicle reported in the literature and different from the experimental pellicles and saliva analyzed. The total natural and experimental pellicles did not contain appreciable amounts of collagen, enamel protein, eukeratin nor haemoglobin but did exhibit some characteristics of a “soft” keratin. Formation of the experimental pellicles from saliva was a selective process. The in vivo and in vitro experimental pellicles were similar in composition, indicating that all the constituents necessary for the formation of a short-term pellicle were present in saliva and that bacteria or their products were not essential.

Acid treatment of organic materials and the removal of calcium carbonate

ABSTRACT Acid treatment alters the carbon content of organic materials. An analysis of the effect of various concentrations of various acids on the carbon content of benzenesulfonamide, crab muscle and salt marsh grass indicates that 5 per cent hydrochloric acid is an appropriate treatment for removing calcium carbonate from organic materials.

High-Concentration Hydrochloric Acid Aids Stimulation Results in Carbonate Formations

Abstract Use of high concentrations of hydrochloric acid in fracture acidizing treatments has solved the stimulation problems in many stubborn reservoirs and has improved results in many others. Treatments of this type were first designed for injection wells in the Aneth field in Utah about a year ago. Their use has now spread to many areas throughout North America. Success of the treatments has led to a re-evaluation of the role of acid concentration in stimulation by acidizing. Extensive laboratory studies and wide-spread field experience have uncovered many new facts concerning acid concentration and have shown that some of the older assumptions are not true at all. This paper presents the technology of acid concentration and factors involved in using high concentrations. Advantages of the strong acid are discussed, as well as the problems (such as inhibition and additive compatibility) encountered in its use. Actual field examples are used to substantiate the work done to the present time. Introduction Use of high-strength hydrochloric acid for fracture acidizing of carbonate-type formations has become extremely popular within the past few months. This popularity is probably an outgrowth of the use of 28 per cent HCl for stimulation of injection wells in the Aneth field in Utah. The strong acid was so successful there that use of higher concentrations of acid spread rapidly to many other areas where more conventional treatment had failed or had shown only limited success. Actually, use of high-strength acid is not new, but lack of technical information and knowledge of how best to use it has limited its past use to occasional isolated cases. Only recently has renewed laboratory and field investigation provided information necessary to properly engineer a treatment using this material. Laboratory studies indicate that at HCl concentrations above 15 per cent, acid properties change significantly with increasing concentration. With a knowledge of what these changes are and where and how they occur, high-strength acid may be used to attain these advantages:greater fracture conductivity resulting in sustained production and injection increases (this is particularly true in reservoirs of high water saturation which make weaker solutions of acid ineffective because of rapid dilution),greater penetration because of more rapid initial decrease in area-to- volume ratio,greater volume of CO2 gas per barrel of reacted acid (this has proved extremely effective in aiding well clean-up), andgreater penetration due to retardation produced by concentration increases of the acid itself and of the reaction products in solution in the partially spent acid. Technical Discussion Fracture acidizing-hydraulic fracturing with acid-is an effective method of improving the production or injection characteristics of many carbonate-type oil- and gas-bearing formations. The success of such fracture treatment depends on two factors: fracture conductivity and depth of fracture penetration. In fracture acidizing, the amount of conductivity depends on both the amount of material removed from the formation and where it is removed along the fracture faces. While many factors control the action of acid in removing the formation material, concentration of the acid can play an important role in increasing conductivity during a fracture acidizing treatment. Of the various types of acid available, 15 per cent hydrochloric acid has long been recognized as a very effective chemical for removing portions of the formation and providing this conductivity. Since the conductivity obtained is proportionately related to the amount of material removed, it is a logical conclusion that if more of the formation is removed the resultant fracture conductivity will be greater. Mathematical calculations show that, in fact, conductivity varies as the cube of the fracture width according to the following equation. JPT P. 1291ˆ

Synthesis of Certain 5-Nitropyridine Derivatives Structurally Related to Some Chemotherapeutic Agents

The condensation of 2-chloro-5-nitropyridine with 1-aminohydantoin, sulfaguanidine, and semicarbazide is described. With sulfaguanidine the N4 derivative was always obtained even under the conditions supposed to afford the N1 derivative. With semicarbazide the condensation in all cases yielded a disubstitution product even when equimolecular amounts of the reactants were used. With aminohydantoin the condensation was effected in 1 per cent hydrochloric acid while in 10 per cent acid no condensation took place, and the haloheterocycle was hydrolyzed to the corresponding hydroxy compound. On the other hand, attempts to condense the halonitropyridine with 3-amino-2-oxazolidone were unsuccessful. The condensation of 2-chloro-5-nitropyridine with 1-aminohydantoin, sulfaguanidine, and semicarbazide is described. With sulfaguanidine the N4 derivative was always obtained even under the conditions supposed to afford the N1 derivative. With semicarbazide the condensation in all cases yielded a disubstitution product even when equimolecular amounts of the reactants were used. With aminohydantoin the condensation was effected in 1 per cent hydrochloric acid while in 10 per cent acid no condensation took place, and the haloheterocycle was hydrolyzed to the corresponding hydroxy compound. On the other hand, attempts to condense the halonitropyridine with 3-amino-2-oxazolidone were unsuccessful.

The Effect of Flow on Acid Reactivity in a Carbonate Fracture

Abstract A definite relationship has been found between the reactivity of flowing hydrochloric acid and its shear rate in a carbonate fracture. Both flow velocity and fracture width affect the acid reaction rate. Laboratory studies were conducted on acid reactivity at different flow velocities through horizontal-linear fractures, using 15 per cent hydrochloric acid at 80F and approximately 1,100 psi. Fracture width varied from 0.02 to 0.20 in. These data provide a new basis from which the spending time and penetration of the acid can be estimated. Equations were derived expressing the relationship between injection rate, fracture width, acid concentration, time and fracture height, for linear and radial fracture systems. Because the penetration of the acid before spending is closely related to the extent of productivity increase resulting from an acidizing treatment, these data provide a valuable insight into some of the controlling factors that must be taken into consideration during treatment preplanning. Introduction Acidizing of carbonate reservoirs to improve production characteristics has been widely practiced since 1932. Originally, it was assumed that the acid uniformly penetrated natural formation pores and flow channels, enlarging them and thereby increasing their flow capacity. Little consideration was given to the reaction rate of the acid, or how far it would penetrate away from the wellbore into the formation, before spending. It has been shown recently that, unless fractures are present in the rock, very little penetration is attained before spending, and the benefits of the acidizing treatment are largely confined to the immediate vicinity of the wellbore. Therefore, acid treatments may be classified into two categories:matrix acidizing, in which the acid flows through multiple formation pores; andfracture acidizing, in which the bulk of the acid travels through fractures in the rock, whether natural or induced. When acidizing treatments are conducted at pressures of sufficient magnitude to open and extend such fractures, it is often desirable to inject a propping agent to hold the fracture open after the treating pressure has been released, thus providing a highly conductive flow channel through the rock. In some cases where acid attack produces surface irregularities, the resulting flow passages can be sufficient to provide high conductivity without use of a propping agent. During injection, the acid dissolves the carbonate rock with which it comes in contact until it is spent. Deeper penetration of the spent acid into the formation produces no appreciable benefit (if no propping agent is used) because the unetched fracture faces will rejoin when treating pressures are released and the fracture will "heal", with negligible resultant conductivity. The spending time of the acid thus becomes important in determining how far from the wellbore the improved- conductivity zone extends. The spending time of acid after injection into carbonate rock depends on the rate at which the acid reacts with the rock. This in turn is controlled by a number of factors, as previously reported. These include temperature, pressure, acid concentration, rock composition, injection rate and the area-volume relationship between the acid solution volume and the surface area of the formation flow channels through which it penetrates. Thus, in matrix acidizing, where an extremely large area is exposed to the acid, spending is rapid. In contrast, spending time is prolonged in open fractures, where the area-volume ratio is much lower. Thus, greatest penetration of the acid before spending will be achieved in acid-fracturing treatments where fractures are held open by hydraulic pressure. Perkins and Kern have presented equations for fracture-width determinations which, for hard formations such as limestone or dolomite, indicate that high injection rates and viscous fluids are required to create wide fractures. Increasing the injection rate will, in itself, produce faster reaction rates. Because this type of reaction can be considered to be first-order diffusion-controlled, the rate of movement of fluid past the rock surface affects the thickness of the diffusion layer, in turn affecting the reaction rate. Staudt, et al, report the results of tests in which a rotating marble cylinder was immersed in acid, and the weight loss at different speeds determined. Such test conditions, however, are not truly indicative of the situation in a formation during an acid-fracturing treatment. JPT P. 409^

Retention of Carbon Dioxide Bubbles on Calcite Etch-Peaks

THE etch-patterns on cleavage faces of calcite which have been reported1–3 bear some interesting similarities and dissimilarities to etch-patterns obtained in this Laboratory. Watts etched calcite for 30 sec. in 1 per cent nitric acid and obtained five-sided figures which he called pits. We immersed calcite in 0.001 N hydrochloric acid for one week and obtained essentially six-sided peaks (Fig. 1) with irregular valleys between them. The sixth side has a rougher surface than the other sides and it seldom extends to the apex of the peak. It may constitute an incompletely formed figure. Stanley used 10 per cent hydrochloric acid for 10–60 sec. and obtained figures which he describes as four-sided, although from his published photographs we detect a tendency of these figures toward the six-sided etch-patterns observed in our study. The Pandyas, using ammonium chloride, obtained parallelograms.

A Bilatriene Pigment in the Green Terebellid Polychæte Eupolymnia heterobranchia (Johnson)

Eupolymnia heterobranchia (Johnson) is a relatively large terebellid found in mud and under boulders on the Pacific coast of North America. All the specimens that I have found near Friday Harbor, Washington, had a deep green colour. This is due to granules of green pigment deposited in the cœlomic cells and in the epidermis. The pigment was readily extracted with acidified methanol, gave a good Gmelin reaction, and reacted positively to the zinc bilipurpurin test. demonstrating that it was a bilatriene. The red-fluorescent compound obtained in the latter test had a sharp maximum at 625 mµ (Unicam), indicating the presence of meso- rather than proto- side chains1. The great resistance of the pigment to concentrated sulphuric acid also distinguished it from biliverdin. In a 5 per cent hydrochloric acid: methanol mixture the absorption spectrum showed peaks at 360 and 675 mµ, resembling mesobiliverdin hydrochloride (363 and 670 mµ; ref. 1).

The Lateral-Line System in the Rio Grande Perch, Cichlasoma cyanoguttatum (Baird and Girard)

The lateral-line system of Cichlasoma cyanoguttatum is similar to that of other perciforms but there are many peculiarities. The tubes of the lateralis scales do not make contact with each other but the innervation of the organs in this part of the system is normal. The exter- nal morphology and osteological components of the system are described in detail and compared with that of serranids and centrachids; the text is copiously augmented with illustrations. The lozenge-shaped canal neuromasts are in general like those of sunfishes but much larger. The sensory cells, unlike most of the cells seen in other fishes, bear multiple sensory hairs. All of the supporting cells penetrate to the free surface of the organ and intercellular bridges connect each with the others, thus forming a kind of syncytium. Cichlasoma cyanoguttatum is the only member of the family Cichlidae known to occur naturally in continental United States. Its range extends eastward from the Rio Grande in Texas as far north as the Rio Colorado near Austin. Material for this study was col- lected from the Blanco River, 25 miles northwest of San Marcos and from San Marcos Springs, Hayes County on July 14, 1958. Dr. Kirk Strawn of Lamar Institute of Technology, Beaumont, Texas, assisted in the collecting and Dr. G. A. Moore of Oklahoma State University offered helpful criticisms. I am grateful for their assistance. Several specimens were fixed in PFA3, one of Allen's modifica- tions of Bouin's fluid, and others in 10 per cent formalin. Three of the formalin-fixed specimens were stained by the alizarin method of Hollister (1934). In addition, four large specimens were packed in dry ice and subsequently disarticulated for bone study. Other formalinized fish were dried by means of jets of air and the canal system injected with India ink. Innervation was determined by gross dissection under the lens of a stereomicroscope. The lachrymal bone was chosen for microscope sections because of its constancy and ease of removal. Material for sectioning was decalcified in two per cent hydrochloric acid, embedded in pyroxylin and cut at five microns. Some sections were stained with iron hematoxylin and others wifth Mallory's triple connective tissue stain; all were mounted in picrolyte. Measurements were taken by means of a filar micrometer mounted on a compound microscope. Drawings were made with the assistance of a camera lucida. EXTERNAL MORPHOLOGY In its external appearance the cephalic lateral-line system of

Potential-Time Curves obtained during the Stress Cracking of Metals

WE have investigated some of the electrochemistry of two 12 per cent chromium martensitic steels while undergoing cracking in acid media. Since it is known that these steels can be made to crack through hydrogen embrittlement as well as by stress corrosion, we were curious as to the cause of cracking in 1 per cent hydrochloric acid with 1 per cent dissolved selenium dioxide. Following the procedure of Brown1, increasingly larger polarizing currents, both anodic and cathodic, were applied to stressed beam specimens to determine which reaction hastened the time to failure. From these results we concluded that the cracking in this medium was by hydrogen embrittlement. Further proof was obtained by substituting sulphuric acid for hydrochloric acid (to eliminate the possible stress corroding influence of the chloride ion) without any change in the pattern of results. Simultaneously with our tests on the effect of applied currents on time to fracture, potential-time curves were automatically recorded. The rather unusual changes in potential we observed are primarily the reason for this communication.