DETERMINATION OF AMMONIA AND AMIDE NITROGEN IN CONNECTION WITH THE CHLORATE METHOD FOR NITROGEN IN PLANT TISSUES

In previous work with the chlorate method (1, 2) for determining nitrogen in plant tissues, materials were used in which the amounts of ammonia and amide nitrogen were either absent or negligible in relation to the total nitrogen present. In working with samples containling significant amounts of ammonia compounds or amide nitrogen, it is necessary to accomiipany the determination with a Nessler test for ammonia. The chlorate oxidation changed all nitrogen in the plants analyzed to nitrate nitrogen with the exception of nitrogen already in the ammonia form or nitrogen in compounds which readily hydrolize to ammonia such as amides. In some studies of nitrogen in plants this may be a decided advantage since this divides the nitrogen into two important groups: 1. Nitrates, alkaloids, proteins, and amino acids the nitrogen in which is oxidized to nitric acid and determined by phenoldisulphonic acid, and 2. Ammonia, amides, and other readily hydrolyzable nitrogen compounds the nitrogen in which is converted to ammonia and determined by the Nessler test. These are the usual compounds to be expected in plants. Of course small amiiounts of the rarer nitrogen compounds may be present, but it is pretty certain in the chlorate oxidation that all nitrogen in plants is either oxidized to nitric acid or caught as ammoniumi sulphate. The same is probably true for allnitrogen compounds in general. It will be shown later that the N in pyridine which is not determined by the regular Kjeldahl procedure was determined by the chlorate method. In the soluble nitrogen test (1) on plant extracts from the more mature conducting tissue of lower petioles of rapidly growing long-day plants, most of the nitrogen is in the form of amino acids or nitrates and for practical use to determine nitrogen deficiencies the Nessler test may be omitted, but for detailed work it should be included. MURNEEK (3) shows that short-day plants contain considerable amide and NH3 nitrogen. Inclusion of the Nessler test enables a more detailed study to be made, since, after treatment with H2SO4 and NaCl03, the phenoldisulphonic test shows all active nitrogen (amino acids and nitrates) present which is in a form for immediate use in the anabolic processes, while the Nessler test shows the reserve nitrogen