Insoluble precipitate formation

The older methods have been replaced by methods which require less, if any, excess sulfuric acid. For example, sulfonation of naphthalene can be carried out in tetrachloroethane solution with the stoichiometric amount of sulfur trioxide at no greater than 30°C, followed by separation of the precipitated l-naphthalenesulfonic acid the filtrate can be reused as the solvent for the next batch (14). The purification of 1-naphthalenesulfonic acid by extraction or washing the cake with 2,6-dimethyl-4-heptanone (diisobutyl ketone) or a C-1—4 alcohol has been described (15,16). The selective insoluble salt formation of 1-naphthalenesulfonic acid in the sulfonation mixture with 2,3-dimethyl aniline has been patented (17). 

Sequestration forms the basis for detergent and water-treatment appHcations of polyphosphates. Sequestration of hardness ions by sodium tripolyphosphate used in detergent formulations prevents the precipitation of surfactants by the hardness ions. Sodium polyphosphate glass (SHMP) may be added to water system to prevent the formation of calcium or magnesium scales by reducing the activity of the hardness ions. However, if the ratio of cation to polyphosphate is too high at a given pH, insoluble precipitates such as may result instead of the soluble polyphosphate complexes. The... 

Silver Thiosulfate. Silver thiosulfate [23149-52-2], Ag 2 y is an insoluble precipitate formed when a soluble thiosulfate reacts with an excess of silver nitrate. In order to minimize the formation of silver sulfide, the silver ion can be complexed by haUdes before the addition of the thiosulfate solution. In the presence of excess thiosulfate, the very soluble Ag2(S203) 3 and Ag2(S203) 3 complexes form. These soluble thiosulfate complexes, which are very stable, are the basis of photographic fixers. Silver thiosulfate complexes are oxidized to form silver sulfide, sulfate, and elemental sulfur (see Thiosulfates). 

Components in the invading water-based filtrate and in the formation waters may react to form insoluble precipitates which can block the pores and give rise to skin damage. The scale can be formed by interaction of calcium-based brines with carbon dioxide or sulfate ions in the formation water. Alternatively sulfate ions in the invading fluid may react with calcium or barium ions in the formation water. Analysis of the formation water can identify whether such a problem may arise. 

Precipitation. The formation of insoluble precipitates which enable the phagocytes to eliminate soluble antigen firm the body. 

Sonication of 0.05 M Hg2(N03)2 solution for 10,20 and 30 min and the simultaneous measurements of conductivity, temperature change and turbidity (Table 9.2) indicated a rise in the turbidity due to the formation of an insoluble precipitate. This could probably be due to the formation of Hg2(OH)2, as a consequence of hydrolysis, along with Hg free radical and Hg° particles which could be responsible for increase in the turbidity after sonication. The turbidity increased further with time. Mobility of NO3 ions was more or less restricted due to resonance in this ion, which helped, in the smooth and uniform distribution of charge density over NO3 ion surface. Hence the contribution of NOJ ion towards the electrical conductance was perhaps much too less than the conduction of cationic species with which it was associated in the molecular (compound) form. Since in case of Hg2(N03)2, Hg2(OH)2 species were being formed which also destroyed the cationic nature of Hg22+, therefore a decrease in the electrical conductance of solution could be predicted. The simultaneous passivity of its anionic part did not increase the conductivity due to rise in temperature as anticipated and could be seen through the Table 9.2. These observations could now be summarized in reaction steps as under ... 

In Nebraska, state regulations require that the chemical makeup of animal feed sold in the state be accurately reflected on the labels found on the feed bags. The Nebraska State Agriculture Laboratory is charged with the task of performing the analytical laboratory work required. An example is salt (sodium chloride) content. The method used to analyze the feed for sodium chloride involves a potentio-metric titration. A chloride ion-selective electrode in combination with a saturated calomel reference electrode is used. After dissolving the feed sample, the chloride is titrated with a silver nitrate standard solution. The reaction involves the formation of the insoluble precipitate silver chloride. The electrode monitors the decrease in the chloride concentration as the titration proceeds, ultimately detecting the end point (when the chloride ion concentration is zero). 

Water has also been shown to be essential for the liquid phase polymerization of isobutylene with stannic chloride as catalyst (Norrish and Russell, 87). The rates of reaction were measured by a dilatometric method using ethyl chloride as common solvent at —78.5°. With a mixture consisting of 1.15% stannic chloride, 20 % isobutylene, and 78.8% ethyl chloride, the rate of polymerization was directly proportional to the amount of added water (up to 0.43% of which was added). A rapid increase in the rate of polymerization occurred as the stannic chloride concentration was increased from 0.1 to 1.25% with higher concentrations the rate increased only gradually. It was concluded that a soluble hydrate is formed and functions as the active catalyst. The minimum concentration of stannic chloride below which no polymerization occurred was somewhat less than half the percentage of added water. When the concentration of the metal chloride was less than about one-fifth that of the added water, a light solid precipitated formation of this insoluble hydrate which had no catalytic activity probably explains the minimum catalyst concentration. The addition of 0.3% each of ethyl alcohol, butyl alcohol, diethyl ether, or acetone in the presence of 0.18% water reduced the rate to less than one-fifth of its normal value. On the other hand, no polymerization occurred on the addition of 0.3 % of these substances in the absence of added water. The water-promoted reaction was halved when 1- and 2-butene were present in concentrations of 2 and 6%, respectively. 

The predicted antiaromaticity in fluoranthene-PAH carbocations (NICS) could well be the origin of the observed paratropicity and proton shielding in these nonalternant-PAH carbocations. The observed broadening in the proton spectra in several cases, the appearance of upfield-shifted broad humps, and the formation of insoluble precipitates (which upon quenching returned the intact PAH) were taken as evidence for the concomitant presence of the RC which could additionally contribute to proton shielding. 

There is much indirect evidence that the above hypothetical mechanism fits the behavior of the soy proteins. Wolf and Tamura (2), while studying the heat denaturation of native IIS soy protein, found that soluble aggregates are formed prior to the formation of insoluble precipitates. They proposed the following mechanism to explain their results. 

Polystyrene-bound carboxylic esters have been reduced with diisobutylaluminum hydride or lithium aluminum hydride. Use of the latter reagent can, however, lead to the formation of insoluble precipitates, which could readily cause problems if reactions are performed in fritted reactors. An alternative procedure for reducing carboxylic esters to alcohols involves saponification, followed by activation (e.g. as the mixed anhydride) and reduction with sodium borohydride (Entries 10 and 11, Table... 

This equation shows that not only a high metal-ion concentration, but also a high pH, often favors the formation of higher polynuclear species, since y generally increases more rapidly than x. For many aqua metal ions, however, the precipitation of insoluble hydroxides sets an upper pH limit, so that in practice it is possible to study the oligomerization reactions only within a narrow pH region defined by the magnitude of the first acid dissociation constant of the monomeric aqua ion and the pH at which insoluble hydroxide formation occurs. 

Barium is an alkaline-earth metal incorporated into bone through the intestinal tract. In terrestrial environments, barium and strontium are approximately equal in abundance. In marine environments, barium forms an insoluble precipitate as a result of the high sulfate content in salt water. Formation of this compound effectively removes barium from seawater. As a result, Ba/Sr ratios reflect diet and are an indicator of trophic position. In human populations, individuals with diets high in marine-based food resources typically have low Ba/Sr ratios in their bone and teeth. Populations who consume large amounts of terrestrial-based food resources tend to have higher Ba/Sr ratios. 

Although it has long been known that benzaldehyde reacts with hydrazine in alkaline solution to give a yellow, insoluble precipitate of benzalazine1 and that the latter when steam distilled in the presence of mineral acids is hydrolyzed to give the corresponding hydrazine salts,2 no previous attempt has been made to apply these facts to the recovery of hydrazine residues. This reaction is practically quantitative and can be applied not only to the recovery of residual hydrazine left in solution in the Raschig synthesis (No. 31) but to all solutions where the detection and recovery of hydrazine in the presence of ammonia, or hydroxylamine, are of interest. In the process of formation of hydrazine salts from benzalazine, 95 per cent of the benzaldehyde can be recovered. 

SDS has several advantages over soap. Unlike the carboxylate anions in soap, the dodecylsulfate anion does not form insoluble precipitates with hard water ions (e.g., Ca2+), leading to the formation of soap scum. Also, the dodecylsulfate anion is the conjugate base of a very strong acid (H2S04). Therefore, SDS is a weak base, and solutions of SDS are pH neutral. 

In the autoxidation of neat hydrocarbons, catalyst deactivation is often due to the formation of insoluble salts of the catalyst with certain carboxylic acids that are formed as secondary products. For example, in the cobalt stearate-catalyzed oxidation of cyclohexane, an insoluble precipitate of cobalt adipate is formed. 18fl c Separation of the rates of oxidation into macroscopic stages is not usually observed in acetic acid, which is a better solvent for metal complexes. Furthermore, carboxylate ligands may be destroyed by oxidative decarboxylation or by reaction with alkyl hydroperoxides. The result is often a precipitation of the catalyst as insoluble hydroxides or oxides. The latter are neutralized by acetic acid and the reactions remain homogeneous. 

Wetlands, at times, may be a poor environment for the formation of metal oxides and/or oxyhydroxides because of the typically low redox potential (Eh). Optimizing the activity of sulfate-reducing bacteria (e.g., desulfovibrio) in the anaerobic zone would be a more effective way of removing metals and sulfates from AD (Kleinmann, 1989). These sulfate-reducing bacteria consume acidity and most of the hydrogen sulfide they produce reacts with heavy metals to create insoluble precipitates. The reactions are shown below ... 

It should be mentioned that most natural aldolase enzymes can also be assayed using enzyme-coupled systems relaying the reaction to a redox process with NAD. The formation of NADH by active microbial colonies in expression libraries of mutant enzymes was detected colorimetrically in agar plates using phenazine methosulfate and nitroblue tetrazolium, which forms an insoluble precipitate. The assay was used by Williams et al. [14] and Woodhall et al. [15] for evolving sialic acid aldolases to accept non-natural aldehyde acceptors. 

The fiuorosulfate dihydrate, PaF2S04 2H2O, analogous to the known uranium(IV) compound (1S2), is precipitated on the addition of aqueous hydrofluoric acid to solutions of protactinium(IV) in dilute sulfuric acid (131). Others (71, 84) have reported the formation of a white, insoluble precipitate in hydrofluoric acid, believed to be a tetrafluoride hydrate, but the product has not been completely characterized. 

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