Phosphate – LaMotte SMART 3 Electronic Soil Lab User Manual

Page 77

SMART3 Soil 1.11

PHOSPHATE

ASCORBIC ACID REDUCTION METHOD • CODE 3653-SC

QUANTITY

CONTENTS

CODE

60 mL

*Phosphate Acid Reagent

*V-6282-H

5 g

*Phosphate Reducing Reagent

*V-6283-C

Pipet, 1 mL, plastic

0354

Spoon, 0.1 g, plastic

0699

*WARNING: Reagents marked with an * are considered to be potential health

hazards. To view or print a Material Safety Data Sheet (MSDS) for these reagents

go to www.lamotte.com. To obtain a printed copy, contact LaMotte by e-mail,

phone or fax.

Phosphorus is necessary for the hardy growth of the plant and activity of the

cells. It encourages root development, and by hastening the maturity of the

plant, it increases the ratio of grain to straw, as well as the total yield. It plays

an important part in increasing the palatability of plants and simulates the

formation of fats, convertible starches and healthy seed. By stimulating rapid

cell development in the plant, phosphorus naturally increases the resistance

to disease. An excess of phosphorus does not cause the harmful effect of

excessive nitrogen and has an important balancing effect upon the plant.

APPLICATION:

0.00-99.00 lb/acre Phosphorus

METHOD:

The diazonium compound formed by diazotization of

sulfanilamide by nitrite in water under acid conditions

is coupled with N-(1-naphthyl)-ethylenediamine

to produce a reddish-purple color which is read

Ammonium molybdate and antimony potassium tartrate

react in a filtered acid medium with dilute solution

of PO

-2

to form an antimony-phosphomolybdate

complex. This complex is reduced to an intense

blue colored complex by ascorbic acid. The color is

proportionate to the amount of phosphate present.

(Only orthophosphate forms a blue color in this test.)

Polyphosphates (and some organic phosphorus

compounds) may be converted to the orthophosphate

form by sulfuric acid digestion. Organic phosphorus

compounds may be converted to the orthophosphate

form by persulfate digestion.

INTERFERENCES:

High iron concentrations can cause precipitation of and

subsequent loss of phosphorus.

Test P

rocedures