LaMotte SMART 3 Electronic Soil Lab - Manual (Page 77)

SMART3 Soil 1.11 77
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
1 Pipet, 1 mL, plastic 0354
1 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
4
-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