Potassium hydroxide, dissolution

B. 3-Hydroxycinchoninic acid. A 3-1., four-necked flask (Note 1) is equipped with a sealed mechanical stirrer, gas inlet tube, gas outlet consisting of a 1-mm. capillary (Note 7), and thermometer. The flask is charged with a freshly prepared solution containing 448 g. (8 moles) of reagent grade (85% minimum assay) potassium hydroxide and 900 ml. of water. The solution (hot from dissolution of potassium hydroxide) is stirred and 147 g. (1 mole) of isatin (Note 8) is introduced. The solid quickly dissolves to give an orange-yellow solution. 

Potassium hydroxide (KOH) (caustic potash) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue... 

A mixture of 17 g of the methiodide and 32 ml of a 40 % aqueous potassium hydroxide solution is heated with stirring in a flask fitted with a condenser. The heating bath should be kept at 125-130°, and the heating should be continued for 5 hours. The cooled reaction mixture is then diluted with 30 ml of water and washed twice with 25-ml portions of ether. The aqueous layer is cautiously acidified in the cold with concentrated hydrochloric acid to a pH of about 2 and then extracted five times with 25-ml portions of ether. The combined extracts are washed twice with 10% sodium thiosulfate solution and are dried (magnesium sulfate). Removal of the solvent followed by distillation affords about 3 g of 4-cyclooctene-l-carboxylic acid, bp 125-12671-1 mm. The product may solidify and may be recrystallized by dissolution in a minimum amount of pentane followed by cooling in a Dry-Ice bath. After rapid filtration, the collected solid has mp 34-35°. 

Sodium hydroxide (NaOH) (caustic soda) Potassium hydroxide (KOH) (caustic potash) Calcium hydroxide (Ca(OH)2) (slaked lime) Ammonium hydroxide (NH4OH) (aqueous ammonia solution) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue White deliquescent solid. Sticks, flakes, pellets. Dissolution In water is highly exothermic. Strongly basic. Severe hazard to skin tissue White powder soluble in water yielding lime water. Alkaline Weakly alkaline. Emits ammonia gas. Severe eye irritant... 

Reaction (II) could be the neutralization of acetic acid by potassium hydroxide, yielding potassium acetate which can be isolated in the crystalline state. On dissolution in water the K+ cation is only hydrated in solution but does not participate in a protolytic reaction. In this way, the weak base CH3COO is quantitatively introduced into solution in the absence of an equilibrium amount of the conjugate weak acid CH3COOH. Thus... 

A solution of 64.9 g. (I mole) of 86.5% potassium hydroxide (Note I) in 28 ml. of water is cooled in an ice bath, saturated with hydrogen sulfide, and flushed with nitrogen to ensure complete removal of excess hydrogen sulfide (Notes 2 and 3). The freshly prepared potassium hydrosulfide solution is diluted with 117 ml. of water and stirred under nitrogen at 55-60°. Then 95.3 g. (0.5 mole) of finely ground tosyl chloride (Note 3) is introduced in small portions at a uniform rate so that the reaction temperature is maintained at 55-60° (Note 2). A mildly exothermic reaction ensues, and the solution becomes intensely yellow. After about 90 g. of tosyl chloride has been introduced, the yellow color disappears, and the dissolution of the chloride ceases. The reaction mixture is rapidly filtered with suction through a warmed funnel, and the filtrate is cooled several hours at 0-5°. The crystals of potassium... 

All four dissolution procedures studied were found to be suitable for arsenic determinations in biological marine samples, but only one (potassium hydroxide fusion) yielded accurate results for antimony in marine sediments and only two (sodium hydroxide fusion or a nitricperchloric-hydrofluoric acid digestion in sealed Teflon vessels) were appropriate for determination of selenium in marine sediments. Thus, the development of a single procedure for the simultaneous determination of arsenic, antimony and selenium (and perhaps other hydride-forming elements) in marine materials by hydride generation inductively coupled plasma atomic emission spectrometry requires careful consideration not only of the oxidation-reduction chemistry of these elements and its influence on the hydride generation process but also of the chemistry of dissolution of these elements. 

According to G. Calcagni, 100 c.c. of a cold 66 per cent, of sodium hydroxide dissolves 24 55 grms. of sulphur or 57 parts of sulphur per 23 parts of sodium while 100 c.c. of a similar soln. of potassium hydroxide dissolves 17 70 grms. of sulphur, or 59 35 parts of sulphur per 39 15 parts of potassium. The soln. reacts for sulphides, polysulphides, thiosulphates, and sulphites. The reaction between alkali hydroxides and sulphur is complex probably sulphides are first formed from which thiosulphates are produced, and by the dissolution of more sulphur, polysulphides the thiosulphates Ipse part of their sulphur forming sulphites. In the more cone. soln. of sulphur part of the latter appears to be uncombined because these soln. yield sulphur to hot benzene. All the soln. are decomposed by carbon dioxide yielding sulphur and hydrogen sulphide. 

Nitrosulphonic anhydride is a white, crystalline solid, of density 2-14. On heating it undergoes partial decomposition 7 it begins to melt at 217° C. to a yellow liquid and distils at about 860° C. The heat of formation, calculated from the heat of dissolution in potassium hydroxide, is 112 Calories ... 

However, there is a strong likelihood of a soluble intermediate in the formation of CdfOHty Cadmium has an appreciable solubility in alkaline solutions 2 x 10-/ mol/L in 8 M potassium hydroxide at room temperature. In general, it is believed that the solution process consists of anodic dissolution of cadmium ions in the form of complex hydroxides. 

If the alternative potassium hydroxide method is employed for the separation of Groups IIA and IIB, the KOH extract may contain As, Sb, Sn, Se, Te, and part of the Mo the residue may contain, in addition to HgS, PbS, Bi2S3, CuS, CdS, and PdS, the gold and platinum partly as sulphides and possibly partly in the form of the free metals. Mo is readily identified by the potassium xanthate or a-benzoin oxime test. The Au and Pt will accompany HgS after extraction with dilute nitric acid upon dissolution in aqua regia, Pt may be identified as the dimethylglyoxime complex in the presence of m hydrochloric acid after the Pb, Bi, Cu, and Cd have been removed. 

Zinc hexammine hydroxide. To 25 ml 0-5m zinc nitrate add 12 5 ml of 2m potassium hydroxide. Filter, wash the precipitate with water, and dissolve the precipitate off the filter with 15 ml 1 1 ammonia. Pour the liquid on the filter several times, until complete dissolution. 

A Hershberg stirrer made of Nichrome wire is the most efficient for aiding dissolution of the potassium hydroxide added after azine formation is complete. 

The dissolution of the potassium hydroxide is strongly exothermic. A small proportion may remain undissolved. 

The 50% (w/w) aqueous potassium hydroxide (KOH) solution is prepared immediately before use in a neoprene bottle. Caution Cooling with a water bath is necessary since dissolution of KOH is very exothermic. 

Chemical stability of carbon over the entire pH range has led to considerable interest in the development of carbon-based stationary phases for RPC. Porous graphitised carbon with sufficient hardness, well-defined and stable pore structure without micropores, which ensures sufficient retention and fast mass transfer can be prepared by a complex approach consisting of impregnation of the silica gel with a mixture of phenol and formaldehyde followed by formation of phenol-formaldehyde resin in the pores of the silica gel, then thermal carbonisation and dissolution of the silica gel by hydrofluoric acid or a hot potassium hydroxide. solution [48. The retention and selectivity behaviour of carbon phases significantly differs from that of chemically bonded pha.ses for RPC. Carbon adsorbents have greater affinity for aromatic and polar substances so that compounds can be separated that are too hydrophilic for adequate retention on a Cix column. Fixed adsorption sites make these materials more selective for the separation of geometric isomers [49]. 

Solubilization has been used for many years in the formulation of phenolic antiseptic and disinfectant solutions. In the case of Cresol and Soap Solution (Lysol) and Chloroxylenol Solution B.P., soap micelles are used to solubilize the phenolic substances. The soap (anionic surfactant) is formed by reaction of potassium hydroxide with a suitable oil such as linseed oil (in Cresol and Soap Solution) or castor oil (in Chloroxylenol Solution). The solubilizing potential of surfactant solutions for hydrophobic species has also been exploited in the design of cholelitholytic solvents for gallstone dissolution with some limited success. 

During electrolysis, per mole of potassium permanganate one mole of potassium hydroxide is produced, which has to be recovered. This can be achieved, for example, by evaporating the mother liquor to 750 g KOH per L, whereupon the dissolved potassium manganate(Vl) and calcium hydroxide crystallize out and are removed. The potassium hydroxide can be returned to the dissolution step. Other dissolved impurities from the ores, such as silicates or aluminates, have to be removed from the alkali cycle. 

The parent compound cyclobutane-1,2-dione itself was proposed as an intermediate in the acid- or base-catalyzed ring contraction of l,2-dichlorocyclobutyl-l,2-diylcarbonate (5), adduct of dichlorovinylene carbonate with ethene under photolysis, which on dissolution in cold dilute potassium hydroxide and subsequent acidification or on dissolution in hydrochloric acid, gave the 1-hydroxycyclopropanecarboxylic acid (6) as a single product. (For other examples of such a reaction, see ref 70.)... 

It is seen from the Table that a process involving the participation of solvated electrons is possible, in principle, for self-dissolution of alkali metals in water. (This process proceeds, of course, parallel to the processes occuring via other mechanisms). In fact, back in 1934, Wolthorn and Femelius had reported that a blue coloration temporarily appeared on the surface of metallic potassium when it reacted with water. This coloration would have been caused by hydrated electrons stabilized in the potassium hydroxide film covering the metal According to Ref. 226, a dark-blue product was formed on reacting alkali metal with ice at — 196 °C, its ESR spectrum had a narrow single line typical of a trapped electron. 

The enthalpy change on dissolution of H2Se(g) in 0.25 M lithium, sodium, or potassium hydroxide was measured by Fabre [1887FAB] with concordant results. From these measurements carried out at about 287 K the review estimates in Appendix A the enthalpy of formation of HSe to be (14.3 3.2) kJ-mol . This result has not been selected since a proper correction from 287 K to standard conditions could not be made. 

---