WHAT IS THE DIFFERENCE BETWEEN THE TEST KIT READINGS OF NITRATE ION AND NITRATE AS NITROGEN?
Many aquarists and pond keepers are perplexed by the use of the terms nitrate ion and nitrate/nitrogen (or nitrate as nitrogen), and do not know what the difference is between the two. The differences between the terms are in how the chemical composition of the same nitrate molecule is being measured, which can be in two different ways, giving two different readings, each of which is correct. If you have a nitrate/nitrogen reading, it can be converted to the ionic nitrate reading by multiplying it by 4.4. If you have an ionic nitrate reading, it can be converted to the nitrogen reading by dividing it by 4.4. For example, if the nitrate ion concentration is 50.0 ppm: 50.0 divided by 4.4 equals11.4. The reading would be 11.4 ppm as nitrate/nitrogen. The conversion factor of 4.4 is based upon the atomic weight proportions of the nitrogen and oxygen in nitrate (4.4 weight units of nitrate contain 1.0 weight units of nitrogen). If the nitrate is measured as the total molecular weight of the
