Heating/cooling methods water bath

Hexammino - cobaltic Chloride, or Luteo-cobaltic Chloride, [Co(NH3)8]Cl3.—Several methods of preparation have been described. The best method is that of Jorgensen,1 whereby the salt is prepared by warming chloro-pentammino-cobaltic chloride, [Co(NH3)5C l]Cl2. in a pressure flask with 20 per cent, aqueous ammonia and ammonium chloride for several hours with constant shaking. After cooling, the mixture is removed from the flask and ammonia allowed to evaporate. The liquid is then diluted, hydrochloric acid added, and the whole heated on the water-bath, thus changing any aquo-pentammino-chloride into ehloro-pentammino-ehloride. More concentrated hydrochloric acid is added and the mixture cooled and filtered. The residue on the filter consists of ammonium chloride, chloro-pentammino-chloride, and hexammino-cobaltic chloride. Ammonium chloride is removed by treating with a 20 per cent, solution of hydrochloric acid, and the residue is then treated on a filter with cold water in which chloro-pentammino-cobaltic chloride is insoluble and hexammino-cobaltic chloride soluble. The salt is precipitated from its warm solution by the addition of half its volume of concentrated hydrochloric acid. 

Dihydro-l//-2-benzotelliirin (Kongalite Method)2 34 g (0.17 mol) of sodium formaldehyde sulfoxylate, 26 g (0.65 mol) of sodium hydroxide, and 100 ml of water are placed in a flask fitted with a stirrer, a reflux condenser, and a nitrogen inlet tube. The flask is flushed with nitrogen, 15 g (0.12 mol) of fine tellurium powder is added, and the mixture is stirred and heated on a water bath for 30 min. 100 ml of ethanol and a solution of 25 g (0.09 mol) of 2-(2 -bromoethyl)benzyl bromide dissolved in 150 mi of hot ethanol are added. The mixture is stirred and heated under reflux for 2 h, the ethanol is distilled off, and the residue is ground, then extracted with a mixture of 300 ml of water and 300 ml of diethyl ether. The diethyl ether layer is separated, washed with water, dried with anhydrous sodium sulfate, filtered, and fractionally distilled yield 8.5 g b.p. 116-12670.3 torr. The residue from the extraction is boiled with 50 m/of ethanol, the mixture is filtered hot, and the filtrate allowed to cool. The crystals are collected (3.8 g) and the combined product fractions are recrystallized from methanol whereby the methanol solution is cooled in dry ice yield 12.3 g (54%) m.p. 64°. 

Dimethyl Tellurium1 (Potassium Hydroxide-Tin(II) Chloride Method A mixture of 100 g (1.78 mol) potassium hydroxide and 180 m/ dimethyl sulfoxide is heated on a water bath. After addition of 10 g (53 mmol) tin(Il) chloride and 60 g (0.47 mol) tellurium powder, the mixture is heated at 120" for 20 h. The mixture is cooled to 40° and 157 g (1.1 mol) methyl iodide are added dropwise over a period of 2 h. The mixture is then heated at 70° for 2 h and then distilled until the condensing vapor reaches a temperature of 100°. The organic layer of the residue is separated from the aqueous layer. The organic layer is dried and distilled at atmospheric pressure yield 97% b.p. 93-94". 

Reagent. Mix 1 g of 2-naphthol with 40 ml of sulphuric acid and heat in a water-bath at 100", with occasional stirring, until the 2-naphthol is dissolved. Method. Mix the sample with 1 ml of the reagent, heat in a water-bath at 100° for 2 minutes, and note any colour produced. Cool, add 1 ml of water, and note the colour again. 

The reducing value is determined by adding 100 pL of the reducing carbohydrate to 100 pL of the working reagent to the wells of a 96-sample microtiter plate. The plate is covered with Saran wrap or some other method to seal the plate and prevent evaporation of the sample and reagent when the plate is heated in a water bath at 80 °C for 35 min. The plate is then cooled for 15 min and the absorbance is measured at 560 nm. Triplicate analyses are usually performed for each sample and for the maltose standards, along with a water blank [175]. 

Method of cooling (ice water bath, freezer, snow, etc.) Heat source... 

Preparation of allyl phenyl ether756 serves as example of Claisen s method of etherification A mixture of phenol (188 g), allyl bromide (242 g), finely powdered potassium carbonate (280 g), and acetone (300 ml) is heated on the water-bath under reflux for 8 h. Potassium bromide separates. After cooling, the mixture is treated with water and extracted with ether. The ethereal solution is shaken with 10% sodium hydroxide solution, dried over potassium carbonate, and evaporated. Distillation of the residue in a vacuum gives the ether (230 g, 86%), b.p. 85°/19 mm. 

Alternate Method-. When 5.1 g. of PO(NHg)3 (see below) is heated on a water bath with 100 ml. of 10% sodium hydroxide for two hours, the following reaction takes place PO (NH g + NaOH = NHg + NaP03(NHg)3. The cooled solution is mixed with 20% perchloric acid until a pH of 6 is reached and the sliver salt is precipitated with 10% AgNO 3 solution the salt is then treated as outlined in method I. [K, Klement and O. Koch, Ber. dtsch. chem. Ges. 87, 333 (1954)]. 

Other laboratory operations performed by the Alexandrian alchemists included solution, filtration, crystallisation, sublimation, and distillation. The art of distillation shows a steady improvement over the years. In the earliest form of distillation apparatus, the vapours ascending fi om the flask or bikos were condensed in the hood or ambix, and then ran down the spout into the receiver (Figure 2.4). The Arabs later used the name alembic for the condensing hood. This method of condensation was inefficient, and it was not until much later that water-cooled condensers were introduced. The alchemists employed several different kinds of furnace, and also introduced the sand bath and water bath for heating purposes. The water bath is reputed to have been invented by one of Zosimos s predecessors called Maria the Prophetess or Maria the Jewess. Today, when a pan of hot water is used to heat another vessel in the kitchen, the contrivance is still called a bain -Marie. 

As an alternative to the extraction procedure described above, small components can be sealed into a double-layered plastic bag made of polypropylene/ polyethylene together with 100 mL of ultra-pure water (SEMI standard method G52-90) and heated in a water bath to 95 °C for 30 minutes. After cooling it... 

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