Organic 2 Review Problem 509

Organic 2 Review Problem 509 - is to be estimated are...

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QUANTITATIVE ANALYSIS 493 0< FIG. 88 (not to scale). Digestion apparatus. The Kjeldhal flasks L of Pyrex glass are shaped as shown with a 50 ml. capacity bulb and a long neck (10 cm. X 1-5 cm.), provided with a small lip or spout. When digestion is proceeding they are supported over a micro-burner by an asbestos-centred gauze, and the top end is lightly clamped so that the flask is tilted slightly to the vertical. The flasks should be supplied with loosely fitting glass stoppers, made by drawing out and sealing off the bottom end of a hard glass boiling-tube. Digestions should always be carried out in a fume-cupboard as considerable quantities of sulphur di- and tri-oxides may be evolved. Digestion. 20-25 mg. of the substance whose nitrogen content
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Unformatted text preview: is to be estimated are weighed out in a stoppered weighing-tube and then transferred to the flask L that has been previously dried in an oven at i2oC. With care, the substance may be transferred directly into the bulb of the flask without any adhering to the sides. If any material sticks on the way down, the flask should be tapped gently to cause the substance to fall to the bottom. 2 G. of the catalyst mix-ture (32 g. of potassium sulphate, 5 g. of mercury sulphate and ig. of selenium powder, well mixed) are added and 3 ml. of A. R. cone. sulphuric acid are measured out carefully and poured into the digestion...
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