On the estimation of nitrates (by aluminium) in water

Abstract

FOR the past sixteen years I have adopted the aluminium method for the estimation of nitrates as the most convenient for the purposes of water analysis, and the following remarks are to be regarded simply as a record of my experience in the working of the process during that period, without laying any claim whatever to originality. I have had so many proofs of the reliability of the procew, its convenience and economy of time, that I have thought the matter worth the attention of the Society of Public Analysts. My procedure is as follows :-I take 70 C.C. of a sample of water, 30 C.C. of a fenper cent. solution of caustic NaHO-of which more presently-and a slip of thin sheet aluminium, weighing about 0.75 grammes ; these are placed in a narrow-mouth vial (402.) the mouth of which is closed with an indiarubber stopper pierced with one hole, in which is inserted a tube 4 inches long, 6 inch diameter, with a drawn out narrower portion about 3 inches long (this latter is inserted in the hole of the stopper), and the wider part is nearly filled with glass-beads. The whole arrangement is then placed under a bell-jar, which may be capacious enough to take several such if desired. As soon as the action is over, and the metal dissolved, the contents are transferred to a 200 C.C. flask and made up to mark with the washings of the beads bottle, &c., and the whole mixed by shaking, Where time is an object, the mixture may be filtered at once (rejecting the first '' runnings,'' and a moderate quantity of the clear liquid diluted to standard bulk and Nesslerized) otherwise the whole is put into an 802. stoppered bottle and allowed to settle for 3 or 4 hours, and a portion of the clear liquid Nessleriwd after proper dilution.