Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays.

  • Albert Bernays
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    149/182 (page 137)
    NITRATES IN WATER; DETECTION AND ESTIMATION. 3. A good uattr.—500 c.c. distilled. Albuminoid NII3. 90c.c -010 60 c.c -002 •012 2 Per litre . . -024 • 000024 grammes per litre. •00168 grains per gallon. Nitrates. The residue of 500 c.c. of the -water is extracted with successive small quantities of distilled water, filtered, and evaporated to a few drops. Frankland's tube is a glass cylinder open at both ends, with a constriction near the top closed by a glass stopcock. The upper part thus forms a small funnel, the lower is graduated. The tube filled up to the stopper with mercury is supported by a clamp in a deep mercury trough. The extract of the water residue is poured into the funnel, the tube raised and the stopcock opened, when the liquid is drawn into the lower portion of the tube. Take care that air does not enter; if it does, depress the tube in the mercury till the air is just expelled. Then rinse the remainder of the soluble water-residue into the funnel with a few drops of water; and repeat with three successive washings of concentrated H2S04, transferring each washing by open- ing the stopcock gently. Now grasp the tube in the hand, closing the lower end with the moistened thumb, and shake sharply, but so as to leave an unbroken column of mercury below. The sulphuric acid will liberate Nitric acid, this with the mercury will give Nitric oxide and mercurous sulphate. Nitric oxide contains half its volume of nitrogen: therefore, if 500 c.c. of water (half a litre) be taken, the amount of nitric oxide per half Litre = the amount of Nitrogen per Litre; i.e. nitrogen existing as nitrates and nitrites, or Oxidized nitrogen. Example. 500 c.c. of the water gave 3'0 c.c. of NO at 19° C. and 773 millimetres pressure; Correcting for temperature and pressure :— 3-0 cc X 773 X 1 760 x [1 + (19° x -003605)] - 2-85 c.c. NO at 0°C and 760 mm. But NO contains half its volume of N, and we have taken half a litre of water. Hence the numher of c.c. of NO found corresponds with the number of c.c. of N per litre. Now 1 litre of hydrogen at 0°C and 760 mm weighs •0896 grm. Nitrogen is 14 times as heavy: 1 litre N=-0896X 14 = 1-25 grin. Therefore 1 c.c. N weighs -00125 grm. In our example, 2-85 c.c. Free NEZ. 50 cc -007 2 Per litre . . -014 _(-000014 grammes per litre. — \ ■ 00098 grains per gallon.