The addition of an alkaline permanganate solution to liquids containing
nitrogenous organic matter causes the formation of ammonia, which can be
distilled and determined by Nesslerization of the distillate. The
nitrogen of the ammonia, thus obtained, is called albuminoid nitrogen.
As the ratio of nitrogenous organic matter to the ammonia obtained by
distillation is decidedly variable[6][30][75] in sewages and other
substances containing much nitrogenous organic matter albuminoid
nitrogen results on such substances are less accurate[29] than organic
(Kjeldahl) nitrogen. Therefore in sewage work, including analysis of
influents and effluents of purification plants and the water of highly
polluted streams, it is recommended that determinations of organic
nitrogen be substituted for determinations of albuminoid nitrogen. For
ground waters and surface waters containing but little pollution, the
albuminoid nitrogen is approximately one-half the organic nitrogen;
accordingly the continuance of albuminoid nitrogen determinations for
this class of work is approved.
_Reagents._—Alkaline potassium permanganate. Pour 1,200 cc. of distilled
water into a porcelain dish holding 2,500 cc., boil 10 minutes, and turn
off the gas. Add 16 grams of C. P. potassium permanganate and stir until
solution is complete. Then add 800 cc. of 50 per cent clarified solution
of potassium hydroxide or an equivalent amount of sodium hydroxide and
enough distilled water to fill the dish. Boil down to 2,000 cc. Test
this solution for ammonia by making a blank determination. Correct
determinations by the amount of this blank.
_Procedure._—After the collection of the distillate for ammonia nitrogen
described on page 15 add 50 cc. (or more if necessary to insure the
complete oxidation of the organic matter) of alkaline potassium
permanganate and continue the distillation until at least four portions,
and preferably five portions, of 50 cc. each, of distillate have been
collected in separate tubes. Determine the albuminoid nitrogen in the
distillate by Nesslerization. If the albuminoid nitrogen is known to be
high it is convenient to collect the distillate in a 200 cc. flask and
to Nesslerize an aliquot part of it.
Dissolved albuminoid nitrogen may be determined in a sample from which
suspended matter has been removed by filtration either through filter
paper or through a Berkefeld filter. Suspended albuminoid nitrogen is
the difference between the total and the dissolved albuminoid nitrogen.