Nitric acid: constant boiling, preparation

Filter Preparation. Currently, for the sake of minimal NASN sample usage, a quarterly composite is constructed from strips from individual filters. A minimum of five samples and not more than seven must be taken per quarter. No two samples shall be taken within the same calendar week. An interval of at least two days must exist between samples. There should be at least one sample and not more than three per month. A composite is oxidized in a low-temperature asher, extracted with mixed (1 3 constant boiling hydrochloric and nitric) acids, the acid extract concentrated and the supernatant taken for analysis. (In some cases... 

To a boiling solution of 0 2 g in 100 ml of water add 50 ml of a solution prepared by refluxing 5 g of bismuth nitrate with 250 ml of water and 7 5 ml of concentrated nitric acid until dissolved, cooling and filtering. Continue to boil for a few minutes, cool, filter, wash the residue with a mixture of one volume of dilute nitric acid and thirty volumes of water and dry to constant weight at 110°. Weight of residue x 0 4863 = propyl gallate. 

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