Lead salt , removal

The central carbon atom is derived from an aromatic aldehyde or a substance capable of generating an aldehyde during the course of the condensation. Malachite green is prepared by heating benzaldehyde under reflux with a slight excess of dimethyl aniline in aqueous acid (Fig. 2). The reaction mass is made alkaline and the excess dimethylaniline is removed by steam distillation. The resulting leuco base is oxidized with freshly prepared lead dioxide to the carbinol base, and the lead is removed by precipitation as the sulfate. Subsequent treatment of the carbinol base with acid produces the dye, which can be isolated as the chloride, the oxalate [2437-29-8] or the zinc chloride double salt [79118-82-4]. 

The lead acetate removes any unreacted m ethyl mercaptan by precipitating it as the lead salt. 

Once a suitably polar plant extract is obtained, a preliminary cleanup is advantageous. The classical method of separating phenolics from plant extracts is to precipitate with lead acetate or extract into alkali or carbonate, followed by acidification. The lead acetate procedure is often unsatisfactory since some phenolics do not precipitate other compounds may coprecipitate and it is not always easy to remove the lead salts. 

Extraction efficiency is not the only factor to be examined in the choice of solvent or reagent for a particular application. Environmental, as well as economic considerations must be taken into account. Solvents such as benzene and chloroform (which have solubilities of 0.07 and 0.82 parts per 100 parts of water) might be preferred for extractive efficiency, but their use would result in large losses to the aqueous phase. Not only would this be expensive, but it would be undesirable for reasons of health the toxic organo lead salts would be removed, but an equally toxic organic solvent would be added to the effluent. Addition of a solvent recovery unit subsequent to the extraction step might render the technique uneconomic (relative to alternative effluent treatment techniques). 

Phenyl isothiocyanate may be prepared in quantity (Expt 6.98, Method 2) by allowing aniline to react with carbon disulphide to form phenyldithiocarbamic acid (cf. 1), which is isolated as the ammonium salt. Treatment of the latter with lead nitrate removes the elements of hydrogen sulphide to produce phenyl isothiocyanate. As indicated in the preparation of p-bromophenyl isothiocyanate which is given as a further example, a slightly modified procedure which requires the use of rectified spirit as a reaction solvent is necessary in order to obtain good yields of isothiocyanates from substituted anilines. 

The serine sulfonate complex can be treated with lead acetate, the insoluble lead salt can be removed by filtration, and the water-soluble fraction can be recovered. The latter is evaporated to dryness and dissolved in 1 ml of distilled water. To this clear solution is added 10 ml of ethanol, and the mixture is stored at 4°C. Crystals form and are collected by centrifugation and dried in vacuo at room temperature. They have the following characteristics [a] + 14.7° (c, 10, in 1 N HC1) m.p. 220°C (with decomposition). These values compare very favorably with a synthetic L-serine. Synthetic D-serine has an [ ]fc - 14.4°. 

After the 15-hour electrolysis process, unplug your power supply, and then open the cell. Carefully remove the clay pot, and then dump its contents into a clean beaker or similar glass container—the anode compartment will contain the insoluble lead-vi-chromate, and some dissolved sodium hypochlorite, and some sodium chloride and potassium hydroxide. The cathode compartment will contain potassium hydroxide, sodium chloride, sodium hydroxide, and some bleach. You can discard the cathode liquid if desired. The lead-vi-chromate can be easily collected by filtering the anode liquid. The collected lead salt should then be air-dried, and then stored in a suitable container. 

Removal of silver salts Warm the insoluble unknown or the residue from 1 (if lead salts are present) with a concentrated solution of potassium cyanide. (If it dissolves completely, only AgCl, AgBr, Agl, and AgCN are present.) Filter and reserve the residue, R, for subsequent treatment. Dilute the filtrate considerably and treat with hydrogen sulphide. Filter off any black precipitate (Ag2S), wash, dissolve in hot dilute nitric acid and add dilute hydrochloric acid. A white precipitate of silver chloride indicates the presence of silver. 

The solution is evaporated to dryness under reduced pressure on a water bath. In order to remove as much hydrochloric acid as possible, the temperature of the bath is raised to 100° toward the end of the distillation. The residue of amino acid hydrochloride and inorganic salts is suspended in 500 cc. of absolute ethyl alcohol. The suspension is boiled on a steam bath for a short time, then cooled to room temperature and filtered on a Buchner funnel. The residue of inorganic salts is washed with 500 cc. of absolute ethyl alcohol. To the combined filtrates is added 400 cc. of ethyl ether (u. s. p. quality) in order to precipitate inorganic material. After several hours the mixture is filtered, and the residue is washed with a 5 2 mixture of absolute ethyl alcohol and ether. The filtrate is transferred to a 5-1. round-bottomed flask, about 200 cc. of water is added, and the liquids are removed by distillation under reduced pressure. The nearly dry residue is dissolved in 2 1. of water, and the solution is treated with an excess of freshly prepared lead hydroxide (Note 5). The suspension is diluted with water to a volume of about 3.5 1. and is then concentrated under reduced pressure, at as low a temperature as possible, to a volume of about 2 1. The suspension is then filtered with suction (Note 6), and the residue of lead salts is washed thoroughly with water. The cloudy filtrate, which still contains some free ammonia, is concentrated by distillation under reduced pressure to a volume of about 300-400 cc. The mixture is filtered, the filtrate is saturated with hydrogen sulfide gas, and the precipitate of lead sulfide is removed by filtration with suction (Note 6). The solution is now concentrated by distillation under reduced pressure on a water bath, and 1 1. of 95 per cent ethyl alcohol is added to the nearly dry residue of the amino acid. The suspension is boiled under a reflux condenser until nearly all the amino acid is dissolved, and the mixture is then allowed to cool to room temperature. The amino acid, which separates in the form of fine needles, is collected on a Buchner funnel and washed with a little 95 per cent ethyl alcohol. A second crop of... 

Place 2 liters of water into a beaker, and then add all the dried sodium salt obtained in step 1. Then heat this mixture to 60 Celsius with stirring. Then dissolve 320 grams of lead nitrate into 1400 milliliters of water, and then slowly add drop-wise, this lead nitrate solution to the sodium salt solution. During the addition, stir the sodium salt solution, and keeps its temperature around 60 Celsius. After the addition, remove the heat source and allow the reaction mixture to cool to room temperature. During the cool down period, continue to rapidly stir the reaction mixture. Afterwards, filter-off the precipitated lead salt, wash with 500 hundred milliliters of cold water, and then vacuum dry or air-dry the lead salt. The result will be 252 grams of the lead salt. 

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