Zinc, chloride, concentrating

Electrodeposition on Other Electrodes Trejo et al. [224] have investigated the influence of the zinc chloride concentration on the zinc nucleation process on GC electrode in KCl solutions under conditions close to those employed in commercial acid deposition baths for zinc. The results show that the nucleation process and the density number of sites are dependent on ZnCh concentration. The deposits are homogeneous and compact, although a change in morphology is observed as a function of ZnCl2 concentration. 

For the determination of the zinc concentration in an unknown solution A, by the method of standard addition, a standard solution B is prepared whose pure zinc chloride concentration is 0.1mmol/l (M = 136.2g/mol, Zn = 65.38). 5.0 ml aliquots of the unknown solution A were introduced into four separatory funnels. 4.0 ml, 8.0 ml and 12.0 ml portions of the standard solution B were added to three funnels. After stirring and extracting (three times), with 5.0 ml of tetrachloromethane containing an excess of 8-hydroxyquinoline, the extracts were diluted to 25 ml. The following fluorescence readings were obtained ... 

Fig. 3.6 Reversible potential of a zinc electrode with respect to a saturated calomel electrode (SCE) as a function of zinc chloride concentration...

Cao et al. [59] used zinc chloride solution (64 wt%) to dissolve wheat straw prior to fractionating the biomass components. With this method, hemicellu-lose was hydrolyzed to its sugar constituents by heating at 60 °C. Cellulose and lignin were recovered as the precipitates upon the addition of water to adjust the solution to 35 % zinc chloride concentration. Cellulose was further hydrolyzed by cellulase to glucose. 

Scheme 8) the erythro threo ratio could be controlled from the zinc chloride concentration and the solvent. ... 

Pure pyridine may be prepared from technical coal-tar pyridine in the following manner. The technical pyridine is first dried over solid sodium hydroxide, distilled through an efficient fractionating column, and the fraction, b.p. 114 116° collected. Four hundred ml. of the redistilled p)rridine are added to a reagent prepared by dissolving 340 g. of anhydrous zinc chloride in a mixture of 210 ml. of concentrated hydrochloric acid and 1 litre of absolute ethyl alcohol. A crystalline precipitate of an addition compound (probable composition 2C5H5N,ZnCl2,HCl ) separates and some heat is evolved. When cold, this is collected by suction filtration and washed with a little absolute ethyl alcohol. The yield is about 680 g. It is recrystaUised from absolute ethyl alcohol to a constant m.p. (151-8°). The base is liberated by the addition of excess of concentrated... 

Lucas reageut is prepared by dissolving 68 g. (0-5 mole) of anhydrous zinc chloride (fused sticks, powder, etc.) in 62 6 g. (0 6 mole) of concentrated hydrochloric acid with cooling to avoid loss of hydrogen chloride. 

By refluxing the alcohol with a mixture of concentrated hydrochloric acid and anhydrous zinc chloride, for example ... 

Reflux a mixture of 68 g. of anhydrous zinc chloride (e.g., sticks), 40 ml. (47 -5 g.) of concentrated hydrochloric acid and 18-5 g. (23 ml.) of sec.-butyl alcohol (b.p. 99-100°) in the apparatus of Fig. 777, 25, 1 for 2 hours. Distil oflF the crude chloride untU the temperature rises to 100°. Separate the upper layer of the distillate, wash it successively with water, 5 per cent, sodium hydroxide solution and water dry with anhydrous calcium chloride. Distil through a short column or from a Claisen flask with fractionating side arm, and collect the fraction of b.p. 67-70° some high boiling point material remains in the flask. Redistil and collect the pure cc. butyl chloride at 67-69°. The yield is 15 g. 

Allyl Chloride. Comparatively poor yields are obtained by the zinc chloride - hydrochloric acid method, but the following procedure, which employs cuprous chloride as a catalyst, gives a yield of over 90 per cent. Place 100 ml. of allyl alcohol (Section 111,140), 150 ml. of concentrated hydrochloric acid and 2 g. of freshly prepared cuprous chloride (Section II,50,i one tenth scale) in a 750 ml. round-bottomed flask equipped with a reflux condenser. Cool the flask in ice and add 50 ml. of concen trated sulphuric acid dropwise through the condenser with frequent shaking of the flask. A little hydrogen chloride may be evolved towards the end of the reaction. Allow the turbid liquid to stand for 30 minutes in order to complete the separation of the allyl chloride. Remove the upper layer, wash it with twice its volume of water, and dry over anhydrous calcium chloride. Distil the allyl chloride passes over at 46-47°. 

Place an intimate mixture of 125 g. of powdered, anhydrous zinc chloride and 26-5 g. of acetophenonephenylhydrazone in a tall 500 ml. beaker in an oil bath at 170°. Stir the mixture vigorously by hand. After 3-4 minutes the mass becomes hquid and evolution of white fumes commences. Remove the beaker from the bath and stir the mixture for 5 minutes. Then stir in 100 g. of clean, white sand in order to prevent solidification to a hard mass. Digest the mixture for 12-16 hours on a water bath with 400 ml. of water and 12 ml. of concentrated hydrochloric acid in order to dissolve the zinc chloride. Filter off the sand and the crude 2-phenylindole, and boil the solids with 300 ml. of rectified spirit. Treat the hot mixture with a little decolourising carbon and filter through a pre-heated Buchner funnel wash the residue with 40 ml. of hot rectified spirit. Cool the combined filtrates to room temperature, filter off the 2-phenylindole and wash it three times with 10 ml. portions of cold alcohol. Dry in a vacuum desiccator over anhydrous calcium chloride. The yield of pure 2-phenylindole, m.p. 188-189°, is 16 g. 

Phenol condenses with phthahc anhydride in the presence of concentrated sulphuric acid or anhydrous zinc chloride to yield the colourless phenolphthalein as the main product. When dilute caustic alkah is added to an alcoholic solution of phenolphthalein, an intense red colouration is produced. The alkali opens the lactone ring in phenolphthalein and forms a salt at one phenolic group. The reaction may be represented in steps, with the formation of a h3q)othetical unstable Intermediate that changes to a coloured ion. The colour is probably due to resonance which places the negative charge on either of the two equivalent oxygen atoms. With excess of concentrated caustic alkali, the first red colour disappears this is due to the production of the carbinol and attendant salt formation, rendering resonance impossible. The various reactions may be represented as follows ... 

Standard EDTA Solutions. Disodium dihydrogen ethylenediaminetetraacetate dihydrate is available commercially of analytical reagent purity. After drying at 80°C for at least 24 hr, its composition agrees exactly with the dihydrate formula (molecular weight 372.25). It may be weighed directly. If an additional check on the concentration is required, it may be standardized by titration with nearly neutralized zinc chloride or zinc sulfate solution. 

Anhydrous zinc chloride can be made from the reaction of the metal with chlorine or hydrogen chloride. It is usually made commercially by the reaction of aqueous hydrochloric acid with scrap zinc materials or roasted ore, ie, cmde zinc oxide. The solution is purified in various ways depending upon the impurities present. For example, iron and manganese precipitate after partial neutralization with zinc oxide or other alkah and oxidation with chlorine or sodium hypochlorite. Heavy metals are removed with zinc powder. The solution is concentrated by boiling, and hydrochloric acid is added to prevent the formation of basic chlorides. Zinc chloride is usually sold as a 47.4 wt % (sp gr 1.53) solution, but is also produced in soHd form by further evaporation until, upon cooling, an almost anhydrous salt crystallizes. The soHd is sometimes sold in fused form. 

Ben zotricbl oride is hydrolyzed to benzoic acid by hot water, concentrated sulfuric acid, or dilute aqueous alkaH. Benzoyl chloride [98-88-4] is produced by the reaction of benzotrichloride with an equimolar amount of water or an equivalent of benzoic acid. The reaction is catalyzed by Lewis acids such as ferric chloride and zinc chloride (25). Reaction of benzotrichloride with other organic acids or with anhydrides yields mixtures of benzoyl chloride and the acid chloride derived from the acid or anhydride (26). Benzo triflu oride [98-08-8] is formed by the reaction of benzotrichloride with anhydrous hydrogen fluoride under both Hquid- and vapor-phase reaction conditions. 

The amine (Imol) is added to a solution of anhydrous zinc chloride (Imol) in concentrated hydrochloric acid (42mL) in ethanol (200mL, or less depending on the solubility of the double salt). The solution is stirred for Ih and the precipitated salt is filtered off and recrystallised from ethanol. The free base is recovered by adding excess of 5-ION NaOH (to dissolve the zinc hydroxide that separates) and is steam distilled. Mercuric chloride in hot water can be used instead of zinc chloride and the salt is crystallised from 1% hydrochloric acid. Other double salts have been used, e.g. cuprous salts, but are not as convenient as the above salts. 

The chloromethylation of thiophene has come somewhat into discredit, partly because of the lachrymatory nature of 2-thenyl chloride, partly because this reaction is highly dependent on the conditions used. Formalin in concentrated hydrochloric acid has been used for chloromethylation, as has the anhydrous system, formaldehyde and hydrogen chloride." The use of a-chloromethyl methylether has also been recommended. The sensitivity of chloromethylation to the experimental conditions is illustrated by the fact that addition of zinc chloride gives di-(2-thienyl)methane as the main product and... 

Zinc chloride is also a catalyst for a liquid-phase process using concentrated hydrochloric acid at 100-150°C. Hydrochloric acid may be generated in situ by reacting sodium chloride with sulfuric acid. As mentioned earlier, methyl chloride may also be produced directly from methane with other chloromethanes. However, methyl chloride from methanol may be further chlorinated to produce dichloromethane, chloroform, and carbon tetrachloride. 

Feitknecht has examined the corrosion products of zinc in sodium chloride solutions in detail. The compound on the inactive areas was found to be mainly zinc oxide. When the concentration of sodium chloride was greater than 0-1 M, basic zinc chlorides were found on the corroded parts. At lower concentrations a loose powdery form of a crystalline zinc hydroxide appeared. A close examination of the corroded areas revealed craters which appeared to contain alternate layers and concentric rings of basic chlorides and hydroxides. Two basic zinc chlorides were identified, namely 6Zn(OH)2 -ZnClj and 4Zn(OH)2 ZnCl. These basic salts, and the crystalline zinc hydroxides, were found to have layer structures similar in general to the layer structure attributed to the basic zinc carbonate which forms dense adherent films and appears to play such an important role in the corrosion resistance of zinc against the atmosphere. The presence of different reaction products in the actual corroded areas leads to the view that, in addition to action between the major anodic and cathodic areas as a whole, there is also a local interaction between smaller anodic and cathodic elements. 

Solutions of EDTA of the following concentrations are suitable for most experimental work 0.1M, 0.05M, and 0.01 M. These contain respectively 37.224 g, 18.612g, and 3.7224 g of the dihydrate per litre of solution. As already indicated, the dry analytical grade salt cannot be regarded as a primary standard and the solution must be standardised this can be done by titration of nearly neutralised zinc chloride or zinc sulphate solution prepared from a known weight of zinc pellets, or by titration with a solution made from specially dried lead nitrate. 

Method A 2.7 g (20 mmol) of zinc chloride are dried in vacuo (0.01 Torr) at 200 C for 2 h. After cooling to 0 C, 150 mL of /-PrOH, 2.4 g (20 mmol) of trimethylsilyl cyanide and, subsequently, 15 mmol of the iV-galactosylimine dissolved in 50 mL of /-PrOH. are added within 15 min. The mixture is stirred for 1.5 h at 0 C, and then allowed to warm to r.t. After evaporation of the solvent in vacuo, the residue is taken up in a mixture of 150 mL of CH,C12 and 100 mL of 1 N HCI acid. The organic layer is extracted with two 100-mL portions of sat. NaHCO, then with water, dried with MgS04 and concentrated in vacuo. The crude product is analyzed by HPI.C. Recrystallization from heptane delivers the pure (R)-diastcrcomcr. 

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