Extractability testing citric acid solution extractant

Shake the vessel containing the test extractant vigorously to obtain a uniform haze of Santonox R in the citric acid solution. Pipette a 25 ml aliquot into a 100 ml separatory funnel, followed by 25 ml of cyclohexane. Shake the separatory funnel vigorously every ten minutes for half an hour. 

Testing is undertaken by several methods, including chloroform extraction and use of a sulfonphthalein dye (absorbance of yellow-colored complex using bromophenol blue and bromocresol green) or the use of eosin (sodium tetrabromofluorescein) solution in acetone and tetrachloroethane solvent. After shaking with a citric acid buffer and eosin addition, upon standing the lower layer turns pink if filmer is present. Subsequent titration with Manoxol OT (sodium dioctyl sulfosuccinate) quantifies the filmer, with loss of the pink color indicating the end point. 

Pour exactly 8mL of extracting solution (f% citric acid in 80% ethanol/water) followed by 4mL of hexane into the test tube. Cap the test tube and shake the mixture, then vortex the mixture for 1 min. 

Detection of other Esters of Fixed Acids [oxalates, tartrates, succinates, citrates).—A certain quantity of the oil (if possible 10-20 c.c. or more) is saponified in the usual way, the excess of alkali being neutralised with hydrochloric acid in presence of phenolphthalein and the alcohol expelled on a water-bath. The residue is diluted with water and extracted with ether, the aqueous solution being tested for oxalic, tartaric, succinic and citric acids by the ordinary analytical methods. 

Triplicate aliquots (0.75 ml) of standard solutions, blanks, and soil extracts are pipetted into labeled 20 ml thick-wall test tubes (15 mm diameter). Citric acid buffer (1.75 ml 0.2 M) is pipetted into each tube. Ninhydrin reagent (1.25 ml) is then pipetted slowly into each tube and vortex-mixed for two seconds. The top of each test tube is loosely covered with aluminum foil and placed in a vigorously boiling water bath for 25 minutes. There should be sufficient water in the bath so that the water level is always above the level of the solutions in the test tubes. The water should return to boiling within 2 minutes of the tubes being placed in the bath. After 25 minutes, the test tube... 

To an aliquot of solution containing not more than 50 /ig of copper in a volume of not more than 25 ml add 2 g of citric acid and 0 5 g of the disodium salt of EDTA. Add 10 per cent solution of ammonia until the pH is approximately 9 (thymol blue). Add 10 ml of a freshly prepared 0 1 per cent solution of sodium diethyldithiocarbamate and extract immediately with three portions, each of 5 ml, of carbon tetrachloride added from a burette, passing each extract through a small filter of cotton wool. A blank should be run with reagents at the same time. Measure the extinction of the mixed extracts at 435 m u and obtain the number of micrograms of copper equivalent to the observed extinctions of the test and blank solutions from a calibration graph prepared as follows ... 

Prepare a standard copper sulphate solution to contain 100 fig of Cu per ml by dissolving 0 3926 g CuS04,5H20 in 2N sulphuric acid, diluted to 1 litre. For use, dilute this solution with 2N sulphuric acid to contain 2 (JLg per ml. Transfer separate 0,1, 2 5, 5, 10,15, 20, and 25 ml portions of this solution made up to 25 ml with 2N sulphuric acid to separators, add 2 g of citric acid and 0 5 g of the disodium salt of EDTA to each and extract with carbon tetrachloride as in the test. Construct a graph relating extinction values to micrograms of copper. 

In a further experiment a synthetic solution of lauric diethanoiamide (40 ppm w/v) in the 5 % citric acid extractant was heated for 10 days at 60 °C) during which time it was considered likely that citric acid would completely hydrolyse lauric diethanoiamide to DBA. The citric acid removal procedure was then applied to the extractant and DBA determined in the column effluent by the periodic acid method. The amount of DBA obtained was that which was expected, assuming lauric diethanoiamide had completely hydrolysed to DBA during the extraction test. Thus, in determining total lauric diethanoiamide plus hydrolysed lauric diethanoiamide in the 5% citric acid extractant, it is unnecessary to apply the preliminary reflux with 0.1 N sulfuric acid prior to analysis by the periodic acid method. 

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