Entrainment distillation as a reference method for the determination of the water content of foods : II. Development of a conveniet method of entrainment distillation
article
The procedure finally adopted is the following. Entrainer: Pure isooctane (2.2.4‐trimethylpentane), bpt. 99° C.
Apparatus: Still of 8 cm diameter, capacity about 150 ml; heating by means of an oil bath kept at about 165° C.
Receiver of the Bidwell‐Sterling‐type; capacity of calibrated part 2 ml, cross section about 0.1 cm^2.
Joints of one brand of glass, ground in. Special features: Cleaning by hot chromic acid mixture; apparatus kept in this medium until use. Bumping is prevented by the use of about 1 g of washed and dried pumice stones of ø_av = 2 mm. Creeping is prevented by the use of two glass wool mats, situated in the vertical tube, connecting still and receiver. Water vapour diffusing from and to the apparatus is caught in a set of moisture control tubes (figures 1 and 3). The main water column and droplets possibly sticking to the glass walls are transported to the calibrated part of the receiver with the help of a defatted copper wire. Accuracy: Calibration on BaCl_2. 2 H_2O yielded a standard‐deviation s = 0.010 g, corresponding to a coefficient of variation C = 10^2 s/ x¯ = 0.55. The average discrepancy between calculated and measured values was 30 mg. "Constant" readings were reliable within less than 10 mg. Time required for reaching constant readings ∼ 7 h.
Apparatus: Still of 8 cm diameter, capacity about 150 ml; heating by means of an oil bath kept at about 165° C.
Receiver of the Bidwell‐Sterling‐type; capacity of calibrated part 2 ml, cross section about 0.1 cm^2.
Joints of one brand of glass, ground in. Special features: Cleaning by hot chromic acid mixture; apparatus kept in this medium until use. Bumping is prevented by the use of about 1 g of washed and dried pumice stones of ø_av = 2 mm. Creeping is prevented by the use of two glass wool mats, situated in the vertical tube, connecting still and receiver. Water vapour diffusing from and to the apparatus is caught in a set of moisture control tubes (figures 1 and 3). The main water column and droplets possibly sticking to the glass walls are transported to the calibrated part of the receiver with the help of a defatted copper wire. Accuracy: Calibration on BaCl_2. 2 H_2O yielded a standard‐deviation s = 0.010 g, corresponding to a coefficient of variation C = 10^2 s/ x¯ = 0.55. The average discrepancy between calculated and measured values was 30 mg. "Constant" readings were reliable within less than 10 mg. Time required for reaching constant readings ∼ 7 h.
TNO Identifier
788493
Source
Recueil des travaux chimiques des Pays-Bas, 70(4), pp. 297-312.
Pages
297-312
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