Desiccants potassium

Potassium Aluminum Sulfate. Potassium aluminum sulfate [7784-24-9]. KAl(SO 12H20, is a white, astringent crystal known as potassium alum, ordinary alum, or potash alum. Its formula weight is 474.39 mp 92.5 °C sp gr 1.75 and solubiUty 11.4 g per 100 mL H2O at 20°C (8). It is soluble in dilute acid and insoluble in alcohol. It dehydrates at about 200 °C to porous desiccated potassium alum [10043-67-1], KAl(SO dried or burnt alum, which has a formula weight of 258.20. 

Required Sulphuric acid, 27-5 ml. aniline, 24 ml. sodium nitrite, 20 g. dry potassium carbonate, 3-4 g. (To ensure that the potassium carbonate is dry, it should be gently heated in an evaporating-basin over a small Bunsen flame for 4-5 minutes with stirring, and then allowed to cool in a desiccator.)... 

To obtain the free acid, dissolve the potassium salt in 50 ml. of cold water, filter the solution if a small undissolved residue remains, and then boil the clear solution gently whilst dilute sulphuric acid is added until the separation of the acid is complete. Cool the solution and filter off the pale orange-coloured crystals of the benzilic acid wash the crystals on the filter with some hot distilled water, drain well, and then dry in a desiccator. Yield of crude acid, 4 g. Recrystallise from benzene (about 50 ml.) to which a small quantity of animal charcoal has been added, filtering the boiling solution through a preheated funnel fitted w ith a fluted filter-paper, as the benzilic acid readily crystallises as the solution cools alternatively, recrystallise from much hot water. The benzilic acid is obtained as colourless crystals, m.p. 150°. 

Sodium and potassium hydroxides. The use of these efficient reagents is generally confined to the drying of amines (soda lime, barium oxide and quicklime may also be employed) potassium hydroxide is somewhat superior to the sodium compound. Much of the water may be first removed by shaking with a concentrated solution of the alkali hydroxide. They react with many organic compounds (e.g., acids, phenols, esters and amides) in the presence of water, and are also soluble in certain organic liquids so that their use as desiccants is very limited... 

Higher alcohols. These may be purified by drying with anhydrous potassium carbonate or with anhydrous calcium sulphate, and fractionated after filtration from the desiccant. Bark corks (or ground glass joints) should be used rubber stoppers are slightly attacked. The boiUng points of the fractions to be collected are as follows —... 

The acetone is refluxed with successive small quantities of potassium permanganate until the violet colour persists. It is then dried with anhydrous potassium carbonate or anhydrous calcium sulphate, filtered from the desiccant, and fractionated precautions are taken to exclude moisture. 

Silver nitrite. Warm concentrated solutions of silver nitrate (containing 48 g. of AgNOj) and potassium nitrite (containing 30 g. of KNOj) are mixed, and the mixture is allowed to cool. The silver nitrite which separates is filtered off and washed with water. It may be recrystallised from water at 70°, and is dried either in a vacuum desiccator or in an air oven at about 40° the yield is about 90 per cent. Silver nitrite should be stored in an tightly-stoppered amber bottle. 

Grind finely pure laboratory grade, anhydrous potassium fluoride, and heat it in an electrically heated oven at 180-210° store in a desiccator. Before use, dry the powdered salt at 180° for 3 hours and grind again in a warm (ca. 50°) glass mortar. 

Into a 500 ml. round-bottomed flask, fitted with a reflux condenser, place 42 g. of potassium hydroxide pellets and 120 g. (152 ml.) of absolute ethyl alcohol. Heat under reflux for 1 hour. Allow to cool and decant the liquid from the residual solid into another dry 500 ml. flask add 57 g. (45 ml.) of A.R. carbon dtsulphide slowly and with constant shaking. Filter the resulting almost solid mass, after cooling in ice, on a sintered glass funnel at the pump, and wash it with two 25 ml. portions of ether (sp. gr. 0-720), followed by 25 ml. of anhydrous ether. Dry the potassium ethyl xanthate in a vacuum desiccator over silica gel. The yield is 74 g. If desired, it ma be recrystallised from absolute ethyl alcohol, but this is usually unneceasary. 

Decant the liquid layer into a 2 5 litre flask, and dissolve the sodium derivative of acetylacetone in 1600 ml. of ice water transfer the solution to the flask. Separate the impiue ethyl acetate layer as rapidly as possible extract the aqueous layer with two 200 ml. portions of ether and discard the ethereal extracts. Treat the aqueous layer with ice-cold dilute sulphimic acid (100 g. of concentrated sulphiu-ic acid and 270 g. of crushed ice) until it is just acid to htmus. Extract the diketone from the solution with four 200 ml. portions of ether. Leave the combined ether extracts standing over 40 g. of anhydrous sodium sulphate (or the equivalent quantity of anhydrous magnesium sulphate) for 24 hours in the ice chest. Decant the ether solution into a 1500 ml. round-bottomed flask, shake the desiccant with 100 ml. of sodium-dried ether and add the extract to the ether solution. Distil off the ether on a water bath. Transfer the residue from a Claisen flask with fractionating side arm (Figs. II, 24, 4r-5) collect the fraction boiling between 130° and 139°. Dry this over 5 g. of anhydrous potassium carbonate, remove the desiccant, and redistil from the same flask. Collect the pure acetji-acetone at 134r-136°. The yield is 85 g. 

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. 

Lead tetraacetate from Merck i Company, Inc. was used. Acetic acid was removed from the reagent at 0.1 m for 24 hr, In the dark. In a desiccator containing potassium hydroxide pellets. 

B. Palladium on carhon catalyst (5% Pd). A suspension of 93 g. of nitric acid-washed Darco G-60 (Note 10) in 1.21. of water contained in a 4-1. beaker (Notes 3 and 4) is heated to 80°. To this is added a solution of 8.2 g. (0.046 mole) of palladium chloride in 20 ml. (0.24 mole) of concentrated hydrochloric acid and 50 ml. of water (Note 2). Eight milliliters (0.1 mole) of 37% formaldehyde solution is added. The suspension is made slightly alkaline to litmus with 30% sodium hydroxide solution, constant stirring being maintained. The suspension is stirred 5 minutes longer. The catalyst is collected on a filter and washed ten times with 250-ml. portions of water. After removal of as much water as possible by filtration, the filter cake is dried (Note 11), first in air at room temperature, and then over potassium hydroxide in a desiccator. The dry catalyst (93-98 g.) is stored in a tightly closed bottle. 

The palladium on carbon catalysts should be dried at room temperature or the carbon may ignite. These catalysts are first dried in air and then over potassium hydroxide (or calcium chloride) in a desiccator. 

Chromium trioxide (chromic anhydride) [1333-82-0] M 100.0, m 197°, dec at 250° to Cr203, d 2.70 (pK 0.74, pK 6.49, for H2Cr04, chromic acid). Red crystals from water (0.5mL/g) between 100° and -5°, or from water/conc HNO3 (1 5). It separates when potassium or sodium dichromate are dissolved in cone H2SO4. Dried in a vacuum desiccator over NaOH pellets hygroscopic, powerful oxidant, can ignite with organic compounds. It is a skin and pulmonary IRRITANT. 

Cobaltous potassium sulfate [13596-22-0] M 329.4. Crystd from water (ImL/g) between 50° and 0°, and dried in a vacuum desiccator over cone H2SO4. 

Potassium ethylxanthate [140-89-6] M 160.3, m > 215°(dec). Crystd from absolute EtOH, ligroin-ethanol or acetone by addition of Et20. Washed with ether, then dried in a desiccator. 

Potassium hexafluorophosphate [ 17084-13-8 j M 184.1, pK 0.5, pK j 5.12 (for fluorophosphoric acid H2PO3F). Crystd from alkaline aqueous solution, using polyethylene vessels, or from 95% EtOH, and dried in a vacuum desiccator over KOH. 

Potassium hydrogen phthalate [877-24-7] M 204.2. Crystd first from a dilute aqueous solution of K2CO3, then H20(3mL/g) between 100° and 0°. Before being used as a standard in volumetric analysis, analytical grade potassium hydrogen phthalate should be dried at 120° for 2h, then allowed to cool in a desiccator. 

Potassium iodate [7758-05-6] M 214.0, pK 0.80 (for HIO3). Crystd twice from distilled water (3mL/g) between 100° and 0°, dried for 2h at 140° and cooled in a desiccator. Analytical reagent grade material dried in this way is suitable for use as an analytical standard. 

Potassium peroxydisulfate (potassium persulfate) [7727-21-1] M 270.3. Crystd twice from distilled water (lOmL/g) and dried at 50° in a vacuum desiccator. 

Potassium thiocyanate [333-20-0] M 97.2, m 172°, pK -1.85 (for HSCN), Crystd from H2O if much chloride ion is present in the salt, otherwise from EtOH or MeOH (optionally by addition of Et20). Filtered on a Buchner funnel without paper, and dried in a desiccator at room temperature before being heated for Ih at 150°, with a final 10-20min at 200° to remove the last traces of solvent [Kolthoff and Lingane J Am Chem Soc 57 126 1935]. Stored in the dark. 

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