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2.5.05AOAC Official Method 955.06

Potassium in Fertilizers

Flame Photometric Method

Final ActionSurplus 9!6

2.1082.113, 14th ed.

(Caution: See 51.007.)

2.0! "ea#ents andApparatus

(a) Ammonium oxalate soln.Dissolve 40 g

(NH4)2C2O4 in 1 L H2O.(b)Methyl red indicator.Dissolve 0.2 g Me red in100 mL l!ohol.

(c)Dilute nitric acid.(1 " 10).

(d) Anion exchange resin.#$%&N 20'(OH)(isher !ienti*i! Co.)+ Dolite -/ or Dolite -41(Dimond hmro!, 1100 erior -ve, Clevelnd,OH 44114)+ ermtit 100 (ermtit Co., $43Midlnd -ve, rms, N 0/562)+ or e7iv.

(e) Potassium nitrate or potassium chloride.#e!r8stlli9e regent grde slt t:i!e *rom H2O nd

dr8 6 hr t 106$.(f)Ion exchange column.Mde *rom '0 !m length

o* std :ll glss t;ing, 2.6 !m od+ one end !losed;81hole No. 4 r;;er stoer thr :hi!h is inserted 2:8 sto!o! or glss t;ing !onne!ted to r;;ert;ing nd !omressor !lm. Do not let sto!o!t;ing rotrde ;ove stoer. Choose stoer lrgeenogh so tht there is no s!e ;et:een stoerverte< nd !olmn :ll. -lterntivel8 se glss!hromtg! t;e '00 = 13 mm id :ith sto!o! orvlve t ;ottom to !ontrol *lo: rte (s!h s >-!ienti*i! ?n!. No. C4226).

l!e glss :ool lg in ;ottom o* t;e, !losevlve, nd dd H2O to ht o* 10 !m. @rns*er ortion o*

resin to

200 mL ;eer nd ssend in H2O. @rns*er slrr8 to

NOH t:i!e, de!nting NOH soln *ter *inltretment. -dd 2 L H2O to resin, stir *e: min, letresin settle, nd de!nt :sh H2O. #eet 'A4 times.#esin is no: in *ree ;se *orm. #egenerte to nitrte*orm ;8 treting ' times :ith HNO' (1 " 13), in smemnner s :ith NOH soln. Bsh resin :ith H2O

ntil H o* :shings is 2 ;8 ;!:shing in !olmnor ;8 stirring nd de!nting in lrge ;eer. toreresin nder H2O in stoered ;ottle.

2.0 Preparation of Solution

(a) Mixed fertilizers and potassium-magnesiumsulfate.Beigh 1.606 g smle into 260 mL vol.*ls (600 mL *ls i* smle !ontins E'0F G2O),

dd126 mL H2O nd 60 mL (NH4)2C2O4 soln, nd ;oil '0min. Cool, dil. to vol., mi

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2.& 'nstrument and ProcedurePerformance (est

Beigh 1.606 g G !id hthlte (rimr8 std+FG2O

2'.0) nd trns*er to 260 mL vol. *ls. -dd ! 0.6 g(NH

4)

2HO

4nd ro!eed s in 2.110(a), ;eginning ...

dd 126 mL H2O ...

#e*s.K . -gri!. ood Chem. 3, 4(1366). -O-C 41,

6''(136)+ 51, 6/(135).

C-/44003/ (otssim)

-O-C ?N@$#N-@?ON-L