Zinc bicarbonate

Fig. 7 Possible structures of zinc bicarbonate species supported by the [12]aneN3 and [12]aneN4 ligands.

Chemical ingenuity in using the properties of the elements and their compounds has allowed analyses to be carried out by processes analogous to the generation of hydrides. Osmium tetroxide is very volatile and can be formed easily by oxidation of osmium compounds. Some metals form volatile acetylacetonates (acac), such as iron, zinc, cobalt, chromium, and manganese (Figure 15.4). Iodides can be oxidized easily to iodine (another volatile element in itself), and carbonates or bicarbonates can be examined as COj after reaction with acid. 

The composition of the builders in an alkaline cleaner is dependent on the metal substrate from which the soil is to be removed. For steel (qv) or stainless steel aggressive, ie, high pH, alkaline salts such as sodium or potassium hydroxide can be used as the main alkaline builder. For aluminum, zinc, brass, or tin plate, less aggressive (lower pH) builders such as sodium or potassium siUcates, mono- and diphosphates, borates, and bicarbonates are used. 

In addition to the materials shown in Table 1, other organic materials find a minor portion of their use in mbber processing, such as waxes and fatty acids. Also, the mbber industry uses modest amounts of inorganic compounds, notably elemental sulfur, zinc oxide, magnesium oxide, and sodium bicarbonate. 

KOH in strikes for zinc die casting is kept below about 3 g/L for Cu strike on zincated Al, sodium bicarbonate is added to lower pH to about 9.8—10.2. 

Water from cooling tower pump suction, pH 8.6-8.8, pressure 20-30 psi (140-210 kPa), flow 2-5 ft/s (0.2 to 1.5 m/s). Dispersant, 1-3 ppm tolyltriazole, sodium hypochlorite 2 hr/day to 0.8 free residual chlorine 0.6-0.8 ppm total zinc and 0.1-0.2 ppm soluble zinc. Free chlorine maintained at 1 ppm for 5 consecutive days/month during the summer. Chemical treatment started after 2 years of no treatment. Water conductivity -612 ( imhos/cm), turbidity 27 NTU (nephelometric turbidity units), chloride 110 ppm, sulfate 50 ppm, carbonate alkalinity (CaCOa) 27 ppm, bicarbonate alkalinity (CaCOs) 118 ppm... 

The presence of the ammonium chloride prevents the coprecipitation of zinc salts when sodium bicarbonate is added to the solution to precipitate the aminoguanidine as the bicarbonate. If the solution is not clear at this step, it should be filtered. 

Estr-5(10)-ene-3a,17 -diol (10 g, 36.2 mmoles) is added over a period of 1 hr to a refluxing mixture consisting of 60 g (0.92 moles) of zinc-copper couple, 350 ml of dry ether and 180 g (54 ml, 0.67 moles) of methylene iodide. After the addition is complete, half of the solvent is removed by distillation and 200 ml dry ether is added. The reaction mixture is then transferred to a sealed stainless steel tube and maintained for 3 hr at 92° before being cooled in an ice bath and poured into 500 ml of saturated aqueous sodium bicarbonate solution. The resultant mixture is extracted with ether and the extracts are dried over anhydrous sodium sulfate and concentrated to yield a solid residue which gives 8.4 g (80%) 5,19-cyclo-5a,10a-androstane-3a,17) -diol mp 161-163° [aJo 40° (CHCI3), on crystallization from acetone. 

Reduction of 6p, 9-Oxidoprogesterone to 9-Hydroxyprogesterone. Zinc powder Note 2) (4. g) is added in small portions to a solution of 2 g of 6)5,19-oxidoprogesterone in 40 ml glacial acetic acid Note i). The mixture is stirred for 40 min, then an additional 4 g zinc is added and stirring is continued for another 40 min at 30°. The cooled solution is filtered, the inorganic residue washed with methanol and the filtrate evaporated under reduced pressure. The resultant crude product is dissolved in 60 ml of chloroform and filtered. Concentrated hydrochloric acid (0.6 ml) is added and the solution stirred for 10 min at 25°. The reaction mixture is diluted with ether, washed successively with water, sodium bicarbonate solution and again with water, dried and evaporated under reduced pressure. The... 

B) t-Butyl 2-Methyl-5-Methoxy-3-lndolylacetate t-Butyl alcohol (25 ml) and fused zinc chloride (0.3 g) are added to the anhydride from Part A. The solution is refluxed for 16 hours and excess alcohol is removed in vacuo. The residue is dissolved in ether, washed several times with saturated bicarbonate, water, and saturated salt solution. After drying over magnesium sulfate, the solution is treated with charcoal, evaporated, and flushed several times with Skellysolve B for complete removal of alcohol. The residual oily ester (18 g, 93%) is used without purification. 

Improved plow steel and extra improved plow steel, bright and galvanized. Use a suitable solvent to remove lubricant. The wires then should be dipped in commercial muriatic acid until thoroughly cleaned. The depth of immersion in acid must not be more than the broomed length. The acid should be neutralized by rinsing in a bicarbonate of soda solution. Fresh acid should be prepared when satisfactory cleaning of the wires requires more than one minute. (Prepare new solution—do not merely add new acid to old.) Be sure acid surface is free of oil or scum. The wires should be dried and then dipped in a hot solution of zinc-ammonium chloride flux. Use a concentration of 1 lb (454 g) of zinc-ammonium chloride in 1 gal (3.8 L) of water and maintain the solution at a temperature of 180°F (82°C) to 200°F (93°C). 

The ways in which inhibitive anions affect the corrosion of zinc are mainly similar to those described above for iron. In inhibition by chromate, localised uptake of chromium has been shown to occur at low chromate concentrations and in the presence of chloride ions Thus under conditions unfavourable for inhibition, pore plugging occurs on zinc. Inhibitive anions also promote the passivation of zinc, e.g. passivation is much easier in solutions of the inhibitive anion, borate , than in solutions of the non-inhibitive anions, carbonate and bicarbonate , A critical... 

Nickel is required by plants when urea is the source of nitrogen (Price and Morel, 1991). Bicarbonate uptake by cells may be limited by Zn as HCOT transport involves the zinc metal-loenzyme carbonic anhydrase (Morel et al., 1994). Cadmium is not known to be required by organisms but because it can substitute for Zn in some metalloenzymes it can promote the growth of Zn-limited phytoplankton (Price and Morel, 1990). Cobalt can also substitute for Zn but less efficiently than Cd. 

X-ray diffraction studies on [TpBut,Me]Zn 2(/i,-r)1,Tj1-C03) have identified that the bridging carbonate ligand is coordinated to each zinc center in a unidentate fashion (171,172), which thereby provides additional support for the presence of a unidentate, rather than bidentate, bicarbonate ligand in [TpBut,Me]Zn(0C02H). The carbonate complex [TpBut,Me]Zn 2(/iA-7)1,T)1-C03) is also characterized by v(CO) absorptions at 1587 and 1311 cm-1 in the IR spectrum (173), and a 13C NMR signal at 8 164 ppm (in C6D6). 

Mn(II)-substituted carbonic anhydrase, which is less active than the zinc enzyme, has also been postulated to exhibit bidentate bicarbonate coordination. 

The reactions of carbon dioxide with zinc hydroxide complexes of the 3-t-butyl 5-methyl and 3,5-di-wo-propyl pyrazolyl derivatives were investigated. IR spectroscopy demonstrated formation of a bicarbonate derivative of the former complex and NMR showed a rapid reversible... 

The X-ray structure of the unsubstituted tris(pyrazolyl)borato zinc nitrate has been solved showing a unidentate coordination mode for nitrate, in contrast with the t-butyl substituted ligand, which shows anisobidentate nitrate coordination due to the steric effects.232 A partial explanation of the reduced activity of cadmium-substituted carbonic anhydrase is offered by Parkin on the basis of the comparison of nitrate coordination to cadmium and zinc trispyrazo-lylborate moieties. A contributing factor may be the bidentate coordination supported by the cadmium that does not allow the facile access to a unidentate bicarbonate intermediate, which could be highly important to carbonic anhydrase activity.233... 

There has been particular recent interest in zinc nitrate complexes as coordination models for bicarbonate binding in carbonic anhydrase. The mono- or bidentate coordination modes have been studied with tris-pyrazolyl borate complexes and can be rationalized in the context of the enzyme activity.433 Caution in this comparison is introduced by ab initio calculations on these model systems demonstrating both monodentate and bidentate coordination energy minima for nitrate binding to zinc 434... 

CO3 species was formed and the X-ray structure solved. It is thought that the carbonate species forms on reaction with water, which was problematic in the selected strategy, as water was produced in the formation of the dialkyl carbonates. Other problems included compound solubility and the stability of the monoalkyl carbonate complex. Van Eldik and co-workers also carried out a detailed kinetic study of the hydration of carbon dioxide and the dehydration of bicarbonate both in the presence and absence of the zinc complex of 1,5,9-triazacyclododecane (12[ane]N3). The zinc hydroxo form is shown to catalyze the hydration reaction and only the aquo complex catalyzes the dehydration of bicarbonate. Kinetic data including second order rate constants were discussed in reference to other model systems and the enzyme carbonic anhy-drase.459 The zinc complex of the tetraamine 1,4,7,10-tetraazacyclododecane (cyclen) was also studied as a catalyst for these reactions in aqueous solution and comparison of activity suggests formation of a bidentate bicarbonate intermediate inhibits the catalytic activity. Van Eldik concludes that a unidentate bicarbonate intermediate is most likely to the active species in the enzyme carbonic anhydrase.460... 

Synthesis of functional models of carbonic anhydrase has been attempted with the isolation of an initial mononuclear zinc hydroxide complex with the ligand hydrotris(3-t-butyl-5-methyl-pyrazolyl)borate. Vahrenkamp and co-workers demonstrate the functional as well as the structural analogy to the enzyme carbonic anhydrase. A reversible uptake of carbon dioxide was observed, although the unstable bicarbonate complex rapidly forms a dinuclear bridged complex. In addition, coordinated carbonate esters have been formed and hydrolyzed, and inhibition by small ions noted.462 A number of related complexes are discussed in the earlier Section 6.8.4. 

The first recognition of a role for zinc in biochemistry was the discovery inl939 that it was an essential component of carbonic anhydrase, a key enzyme in erythrocytes that catalyses the formation of bicarbonate ... 

---