Segmented Flow AutoAnalyzer system consisting of:
1. Auto sampler
2. Proportionating pump
3. Phosphorus manifold
4. Colorimeter

Stock Solution:
1. 1000 ppm P: Use certified, NIST traceable plasma grade standard.
Instrument calibration standards:
1. Pipet the designated amounts of 1000 ppm P stock solution into 1 liter volumetric flasks. Dilute to volume with deionized water and mix well.

Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
1	1	1	8
2	5	5	40
3	20	20	160
4	40	40	320

Ascorbic Acid Solution:
1. Weigh 17.6 g ascorbic acid into a 1 liter volumetric flask containing 700 mL deionized water and dissolve.
2. Add 50 mL acetone and dilute to volume with deionized water.
3. Add 0.50 mL (10 drops) Levor IV and mix well.
Sulfuric-Molybdate solution:
1. Weigh 10 g ammonium molybdate into a 1 liter volumetric flask containing 600 mL deionized water and dissolve.
2. Slowly add 62 mL sulfuric acid. CAUTION: this reaction is exothermic and may cause the solution to spatter if the sulfuric acid is added too rapidly.
3. Let cool. Dilute to volume with deionized water and mix well.

Calibrate the instrument using the instrument calibration standards, followingthe procedures given in the instrument manual.
Analyze the Mehlich I extracts on the AutoAnalyzer using a 660 nm filter.
Analyze samples, quality control sample, calibration checks, and redipped samples in the same order as that given for the ICP Soil 180 method for extractable P, K, Ca, Mg, Zn, and Mn, page 10.

Use the same quality control parameters as those given in the ICP method for extractable P, K, Ca, Mg, Zn, and Mn, page 16.

Isaac, R. A. and J. B. Jones. 1970. AutoAnalyzer systems for the analysis of soil and plant tissue extracts. In Technicon International Congress.
Technicon AutoAnalyzer II. 1973. Ortho Phosphate In Water and Wastewater. Industrial Method No. 94-70W. Technicon Industrial Systems.