Solute and evaporation

Vanillin Suga.r, This product is prepared by dry mixing or impregnating the sugar with a vanillin alcohol solution and evaporating the alcohol. However, modem techniques increasingly involve grinding the sucrose and vanillin mixture very finely. 

Cyclooctane Sulfide To 12.5 g (0.06 mole) of the dichlorosulfide in 150 ml of ether is added 1.2 g (0.03 mole) of lithium aluminum hydride in 60 ml of ether at a rate so as to maintain a gentle reflux (about 20 minutes). The mixture is allowed to stand overnight and is then cautiously treated with water to decompose the excess hydride. The mixture is mixed with fuller s earth (Floridin) and is filtered, and the filtrate is dried over anhydrous magnesium sulfate. Filtration of the solution and evaporation of the solvent (rotary evaporator) gives about 7 g of the colorless crystalline solid, mp 170-171°. It may be recrystallized from aqueous methanol, mp 172-173°. 

The procedure given above is applied to norbornene. However, the formation of the alcohol is accompanied by formation of moderate amounts of the acetate. Therefore, the dried tetrahydrofuran solution of the alcohol-acetate mixture is treated with 0.4 g (O.OI mole) of lithium aluminum hydride dissolved in 10 ml ofTHF. The excess hydride is decomposed by careful addition of water, followed by filtration, drying of the organic solution, and evaporation of the solvent. The residue is almost pure (>99.8%) exo-1-norborneol. It may be purified by direct distillation, bp 178-17971 atm, crystallizing slowly on cooling, mp 127-128°. 

The main requirements for a coating are that it is easy to apply (i.e., low viscosity) and dries to a non-tacky finish within a reasonable time. Originally, this equated to the solution and evaporation of the solvent. However, because of environmental concerns, formulations have tended to shift the concentration of solvents from 80% to less than 20% (known as high solids coatings). Many industrial processes use polymer powders (of approximately 40 pm diameter),... 

Standard preparation Dissolve an accurately weighed quantity of USP Miconazole Nitrate RS in a mixture of chloroform and methanol (1 1) to obtain a solution having a known concentration of about 0.8 mg/mL. Transfer 5 mL of this solution to a test tube, add 2 mL of Internal standard solution, and evaporate at a temperature not higher than 40 °C with the aid of a current of nitrogen to dryness. Dissolve the residue in 2 mL of a mixture of chloroform and methanol (1 1), and mix to obtain a Standard preparation having a known miconazole nitrate concentration of about 2 mg/mL. 

Preparation. Put 3.5 g of sodium sulphite and 50 ml of water into a small conical flask. Weigh 2.5 g of flowers of sulphur and, after wetting the sulphur with ethanol (why ), transfer it into the flask with the sodium sulphite solution. Heat the mixture up to boiling. The end of the process is featured by a neutral reaction of the solution with litmus. Filter the hot solution and evaporate it on a water bath up to the beginning of crystallization. Filter off the crystals that precipitated after cooling in a Buchner funnel. Write... 

Treat the product with hot water, filter the solution, and evaporate it until crystals form. Let the cooled solution stand for crystallization. Pour a drop of the hot saturated solution onto a slide, examine the formed crystals under a microscope, and draw their shape. 

Preparation of Potassium Chromate. (Perform one experiment on each table.) Melt a mixture of 1 g of potassium carbonate, 1 gof potassium hydroxide, and 2 g of potassium nitrate in an iron crucible by heating with the flame of a burner. While stirring the melt with an iron wire, introduce 1 g of finely comminuted chromite or -0.8 g of chromium oxide into the crucible. Roast the mixture for 5-10 minutes on a blowpipe. Treat the cooled melt with water. Filter the solution and evaporate it until a crystalline film appears. What is the composition of the formed crystals Why was potassium carbonate introduced into the reaction Write the equation of the reaction. 

Preparation of Sodium Paramolybdate. Pour 20 ml of a sodium molybdate solution into a 100-ml beaker. Heat the solution and introduce freshly precipitated molybdic acid into it in small portions with stirring until it stops dissolving. Filter the solution and evaporate it in a water bath until crystallization of a sample taken begins. 

Preparation of Mohr s Salt. Perjorm the experiment in a jume cupboard ) Put one gramme of a finely cut iron wire into a flask and dissolve it with heating in the calculated amount of 2 A sulphuric acid. Insert a funnel into the neck of the flask (for what purpose ). Keep the volume of the solution constant. After dissolving the metal, filter the solution and evaporate it until a crystalline film begins to form on its surface. What substance is in the solution ... 

Normal chromates of vanadium have not been prepared. An ammonium vanadochr ornate, 2(NH4)2O.V808.2Cr03.7HaO, has been prepared in red crystals by dissolving vanadium pentoxide in ammonium chromate solution and evaporating at ordinary temperatures in vacuo.6... 

Hydroxide. Potassium hydroxide, [CAS 1310-58-3]. caustic potash, potassium hydrate, KOH, white solid, soluble, mp 380 C, formed (1) by reaction of potassium carbonate and calcium hydroxide in H2O, and then separation of the solution and evaporation. (2) by electrolysis of potassium chloride under the proper conditions, and evaporation. Used in the preparation of potassium salts f 1) in solution, and (2) upon fusion. Also used 111 the manufacture of (3) soaps, (4) drugs. (5) dyes, (6) alkaline batteries, (7) adhesives, (8) fertilizers, (9) alkylates, (10) for purifying industrial gases, (11) for scrubbing out traces of hydrofluoric add in processing equipment, (12) as a drain-pipe cleaner, and (13) in asphalt emulsions. 

Oleate. Sodium oleate, [CAS 143-19-1], NaCi H33 02, white solid, soluble, froth or foam upon shaking the H40 solution (soap), formed by reaction of NaOH and oleic add (in alcoholic solution) and evaporating. Used as a source of oleate. 

The precipitate (tannate of iron) is dissolved in dilute sulphuric add and the solution thus obtained extracted with ethyl acetate, the ethereal liquid being then separated from the aqueous solution and evaporated to dryness. The residue (tannic add) is dissolved in water and identified by means of dilute ferric sulphate or ferric alum solution (blackish-blue coloration). If the ink contains logwood, part of this passes with the tannin in such case, to identify the tannin in the aqueous solution of the ethyl acetate extract, distinctly alkaline ammoniacal copper sulphate is added, this giving a pretipitate in presence of tannin. 

Recently, Corey and coworkers prepared the cinchonidine-derived bifluoride 20 from the corresponding bromide by passage of a methanolic solution through a column of Amberlyst A-26 OH- form, and subsequent neutralization with 2 equiv. of 1 N HF solution and evaporation (the modified method C in Scheme 9.5). The catalytic activity and chiral efficiency of 20 (dried over P205 under vacuum) have been demonstrated by the development of a Mukaiyama-type aldol reaction of ketene silyl acetal 21 with aldehydes under mild conditions, giving mostly syw-P-hydroxy-a-amino esters 22 as the major diastereomer with good to excellent enantiomeric excesses (Table 9.4) [23],... 

Dry the combined ethereal phases (MgS04), filter the solution, and evaporate the solvent on a rotary evaporator. Distil the residue to obtain the title compound (b.p. 105-108°C/16 mmHg, 1.27 g, 72%). 

At 20°C, a saturated solution of calcium sulfate, CaS04, has a concentration of 0.0153 mol/L. A student takes 65 mL of this solution and evaporates it. What mass (in g) is left in the evaporating dish ... 

In the early part of the 1800s chemists in Europe took willow leaves and boiled them with different solvents to try to extract the active ingredients. In 1825 an Italian chemist filtered such a solution and evaporated away the solvent. He obtained impure crystals of a compound containing some of the active ingredient. Repeated recrystallization and refinement of his experimental technique produced a pure sample of the unknown material (Figure 1.1). 

Acidity (as acetic acid) Mix 38 mL of sample with an equal volume of carbon dioxide-free water, add 0.1 mL of phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Not more than 0.1 mL is required to produce a pink color. Aldehydes (as formaldehyde) Prepare a Sample Solution by diluting 2.5 mL of sample with 7.5 mL of water. Prepare a Standard Solution containing 40 p,g of formaldehyde in 10 mL of water. Add 0.15 mL of a 5% solution of 5,5-dimethyl-1,3-cyclohexanedione in alcohol to each solution, and evaporate on a steam bath until the Acetone is volatilized. Dilute to 10 mL with water, and cool quickly in an ice bath while stirring vigorously. Any turbidity produced in the Sample Solution does not exceed that produced in the Standard Solution. 

Allow the mixture to stir for another 2 h, then adddrytetrahydrofuran (50 mL), filter the resulting brown solution, and evaporate the filtrate on a rotary evaporator. Purify the remaining crude product first by column chromatography on silica gel 60 (20 g) with Et20/hexane (1 3, v/v) to remove triphenyl-phosphane oxide and finally by vacuum distillation of the crude oily product to furnish pure 2 as a colourless oil, b.p. 62°C/0.6 mm Hg, 1.62 g (56%). 

Redissolve this material in dry dioxane (54 ml), transfer the solution to a single-necked round-bottomed flask (100 mL), flush it with nitrogen, and add polymeric Hunig s base (4.55 g) followed by triphenylphosphane (1.42 g, 5.4 mmol). Stir the resulting mixture at 50°Cfor 15 h under nitrogen. Filter the solution and evaporate the solvent under reduced pressure. Purify the residual crude product 9 by column chromatography on silica gel 60 (toluene/ethyl acetate, 2 3 v/v /fy = 0.4). Yield 1.1 g (62%). 

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