Electrolytes, precipitation

Electrolytic Precipitation. In 1800, 31 years before Faraday s fundamental laws of electrolysis, Cmikshank observed that copper metal could be precipitated from its solutions by the current generated from Volta s pile (18). This technique forms the basis for the production of most of the copper and 2inc metal worldwide. 

Precipitated by higher concentration of electrolytes. Precipitated by low concentration of electrolytes. 

Many electrolytes precipitate starch iodide from solution.27,95,96... 

In the electrolytic precipitation of the gold an iron anode and a sheet-lead cathode are employed, the current-density being very low, about 0 5 amp. per sq. mdtre.1 The gold is deposited on the lead, and after removal of this metal still contains a considerable proportion of both lead and silver. It is freed from them by the operation called parting. ... 

Table 1 points to a further important aspect of water-free organic electrolyte systems. The limiting potential, i. e., the value at which the organic solvent decomposes, shows a far broader applicable voltage window than aqueous systems. Furthermore, aromatic solvents which, except for toluene, are not listed in Table 1, such as naphthaline and diphenyl, have considerably wider voltage windows (3.91 and 4.28 V [81], respectively), than the solvent water. Such extensive voltage windows offer the capability of depositing metals which cannot be electrolytically precipitated from aqueous solution. 

The same investigation showed that copper-precoated ceramic plates coated with aluminum can be etched like copper circuit boards. A comparative study of galvanoaluminum layers and other electrolytically precipitated deposits was recently published [140]. 

Table 30-1 lists a variety of separation methods that are in common use, including (1) chemical or electrolytic precipitation, (2) distillation, (3) solvent extraction, (4) ion exchange, (5) chromatography, (6) electrophoresis, and (7) field-flow fractionation. The first four are discussed in Sections 30A through 30E of this chapter. An introduction to chromatography is presented in Section 30F. Chapters 31 and 32 deal with gas and liquid chromatography, respectively, while Chapter 33 deals with electrophoresis, field-flow fractionation, and other separation methods. 

Electrolytic precipitation is a highly useful method of accomplishing separations. In this process, the more easily reduced species, either the wanted or the unwanted component of the sample, is isolated as a separate phase. This method becomes particularly effective when the potential of the working electrode is controlled at a predetermined level (see Section 22B). 

The hydroxide, Th(OH)<, is precipitated as a gelatinous white mass when an alkali hydroxide or ammonia is added to solutions of a thorium salt. It is readily soluble in acids, forming salts, and in solutions of alkali carbonates, forming complex carbonates. It is not soluble in the alkalies, hence thorates are unknown. It is easily obtained as a positively charged colloid from which small quantities of electrolytes precipitate it. 

Parker D. E., Glatz C. E., Ford C. F., Gendel S. M., Suominen I., Rougvie M. A. Recovery of a charged-fusion protein from cell extracts by poly electrolyte precipitation. Biotechnology Bioeng. 1990 36 467-475. 

This technique is of particular advantage where quantitative separation of the desired conqx>und is not feasible, as illustrated already by de Hevesy in 1932 In determination of micro amounts of lead by anodic precipitation, quite varying results were obtained. By addition of a known amount of "radiolead and measuring the radioactivity of lead at the anode, the yield of the precipitation could be determined, and although the electrolytic precipitation was inefficient - an exact analysis was obtained. 

The processing and surface preparation of silver particles is critical to their performance as a filler. The first step in manufacturing silver flakes is to produce silver powder. Powdered silver may be produced by chemical precipitation, electrolytic precipitation, or melt atomization. Most commercially available silver powders are precipitated by reducing silver from a silver nitrate solution. Particle sizes of powdered silver range from submicron to 5 pm." Silver powders are selected based on size and... 

Similarly, titanium diboride (TiB2) is electrolytically precipitated from a borax melt with titanates and Ti02 900°C. 

In the formula equation (1), compounds are written in their molecular, or formula, expressions. In the total ionic equation (2), compounds are written to show the form in which they are predominantly present strong electrolytes as ions in solution and nonelectrolytes, weak electrolytes, precipitates, and gases in their molecular forms. In the net ionic equation (3), only those molecules or ions that have reacted are included in the equation ions or molecules that do not react (the spectators) are omitted. 

The reduction of analysis time was the most important, although unintended, result of Smith and Exner s research. Electrolytic precipitation using the old methods usually took from three to twelve hours, and Smith regularly applied electric current to solutions for the entire night. The rotating anode with its more powerful current accomplished complete electrolytic separations in ten to twenty minutes, a significant reduction indeed. 

Withrow, J. R. "The Electrolytic Precipitation of Gold with a Rotating Anode and the Rapid Analysis of Halide" Ph.D. Thesis, University of Pennsylvania, 1905. 

In a typical example (77), 200 parts water, 100 parts VF, 0.6 parts of a perflu-orinated carboxylic acid, 0.2 parts ammonium persulfate, and 3 parts water glass (Na20/Si02 = 1 3.3) are introduced into a stirred autoclave. The mixture is heated to 46°C, the pressure is brought to 4.3 MPa (42.5 atm), and held for 8 h. Addition of an electrolyte precipitates a white powdery PVF at 95% 5field. 

In some cases due to the composition of the deposition electrolyte, precipitation of metal hydroxides, sulphides, or sulphur is inevitable. This is a major issue in wet chemical methods such as electrodeposition and chemical bath deposition (CBD). In CBD in particular, the deposition electrolyte becomes useless after the first round of deposition, and a large amount of waste is consequently generated. This batch process makes this technique more expensive considering the amount of resources required... 

The precipitate was again dissolved in hydrochloric add. Now a copper foil was introduced. A precipitate was obtained even now, but small and almost invisible - small, but the carrier of the whole activity. This precipitate was again dissolved in hydrochloric acid and something unknown in the solution was precipitated by addition of stannous chloride SnClj. When filtered off, it was shown that its radioactivity was 3500 times greater than that of pure uranium. A further purification was made by hydrogen sulfide precipitation, dissolution and finally electrolytic precipitation. 

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