Thermal conductivity sodium hydroxide

Some unsaturated ketones derived from acetone can undergo base- or acid-catalyzed exothermic thermal decomposition at temperatures under 200°C. Experiments conducted under adiabatic conditions (2) indicate that mesityl oxide decomposes at 96°C in the presence of 5 wt % of aqueous sodium hydroxide (20%), and that phorone undergoes decomposition at 180°C in the presence of 1000 ppm iron. The decomposition products from these reactions are endothermic hydrolysis and cleavage back to acetone, and exothermic aldol reactions to heavy residues. 

The soft drink is initially cooled to 4°C in a fridge. The container is then opened and an aliquot of concentrated sodium hydroxide (40%) is added to quench the carbon dioxide in the product (typically 10 ml of NaOH is added to 284 ml of product). The carbon dioxide is quenched by reaction with the sodium hydroxide to form bicarbonate and carbonate ions. An aliquot (50 /a/) of the quenched product is removed and pipetted into the corning instrument s cell. The cell is closed and the solution acidified to release the carbon dioxide, which is then detected by the change in the thermal conductance of the vapour phase. 

An example can be given to illustrate the operation of the Perkin-EImer CHN analyser. A sample of about 3 mg was burned in oxygen, then a flow of helium took the products through a layer of catalysts to a mixer. The pressure in the mixer was maintained at 2 atm. A portion of gas was then directed from the mixer to the measuring part of the instrument, consisting of three thermal conductivity detectors and two absorbers. The first absorber contained magnesium perchlorate for absorption of water the second contained sodium hydroxide for absorption of carbon dioxide. 

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