Plants & Human Affairs (BIOL106)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Calculating the Concentration of Nitrogen in a Solution

I.  Liquid.

• use C₁V₁ = C₂V₂ equation
• where c= concentration and v = volume
• multiply by 10,000 to convert to mg N/liter (converts parts per hundred to parts per million)
• units must be equivalent (1 tsp = 4.93 ml; 1 qt = 946 ml)

    Examples:    

1. Ortho Aftican Violet (6-9-5) add 1 tsp to 2 qts water
   
        =(6%) (5 ml) = x (2000 ml)
        x = 0.015% x 10,000 = 150 mg N/liter
   
    

2. Marsh�s VF-11 Brand (0.15-0.37-0.46) � 1 tsp liquid per qt 

             complete the calculation

II. Soluble

• mg N/L = (amount used in mg x %N)/vol water used (liters)

• units must be equivalent � need to know mass of fertilizer in mg

     Examples:

1. Miracle Gro (15-30-15) � 1 tsp (assume 1 tsp = 2800 mg) to 1 gal water
           =(2800 x 0.15)/3.78 liters
           =111.1 mg N/liter
   
    

2. Peters Professional (20-20-20) � 1 tsp to 1 gal water

                another for you to do

Reference:

This exercise is adapted from Hershey, D (1990) Sleuthing the nutrients that make your houseplants grow.  Science Activities 27: 17 � 20.

Last updated:  01/11/2005  � Copyright  by SG Saupe