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topic 39558

Sodium Dichromate Testing?



2006

Looking for an easy test for concentration on sodium dichromate in my passivate tank. Makeup of tank consist of just nitric and sodium dichromate.

Also wondered if using a simple concentration nitric test would be effected by the presence of the sodium dichromate or if the results would be consistent as if you had only nitric in the bath ?

Thanks,

John Doyle
PM Industries - Springdale, Arkansas


2006

John

I pulled this recipe off this website a while ago. I apologize for not being able to credit the original author. I hope this is what you are looking for.


Here are the two analyses with calculations for a Type II, QQ-P-35C [link is to free spec at Defense Logistics Agency, dla.mil], passivation
solution.
SCOPE: To determine the concentration of Sodium Dichromate in a solution.
EQUIPMENT:
2 mL Pipet
25 mL Buret
250 mL Erlenmeyer Flask Deionized Water
0.1 N Sodium Thiosulfate
100 mL Graduated Cylinder
0.5% Starch Indicator
10 mL Graduated Cylinder
Concentrated Sulfuric Acid
10% w/v Potassium Iodide
1.000-1.250 Hydrometer
500 mL Graduated Cylinder
PROCEDURE:
Using the pipet, transfer 2 mL of the sample into the Erlenmeyer flask. Using
the graduated cylinder, add 100 mL deionized water to the flask. Using the
graduated cylinder, add 5 mL concentrated sulfuric acid and 10 mL potassium
iodide solution to the flask. Titrate with 0.1 N sodium thiosulfate until the
solutions turns to a straw color. Add 2 mL starch indicator to the flask and
continue to titrate until the blue-black color disappears. Record the mL used as
V1. Place 500 mL of sample in the graduated cylinder. Measure the density of the
solution with the hydrometer. Record this value as "P".
CALCULATION:
C1= (V1*F1*N1)/P
C1 = Concentration of Sodium Dichromate in %w/w.
V1 = mL of sodium thiosulfate used in the titration
F1 = 2.483
N1 = Normality of sodium thiosulfate used in the titration.
P = Density of the solution
REPLENISHMENT:
W1 = P*V2
W2 = (C1/100)*W1
W3 = (C2/100)*W1
W4 = W3-W2
V3 = W4/453.6
P = Density of the solution.
V2 = Volume of the solution in milliliters.
W1 = Weight of the solution in grams.
C2 = Optimum concentration of Sodium Dichromate %w/w.
C1 = Actual Concentration of Sodium Dichromate in %w/w.
W2 = Weight of Sodium Dichromate in solution in grams.
W3 = Optimum weight of Sodium Dichromate in grams.
W4 = Weight of Sodium Dichromate to add in grams.
V3 = Weight of Sodium Dichromate to add in pounds.
DILUTION:
W1 = P*V2
W2 = (C1/100)*W1
W3 = (C2/100)*W1
W5 = W2-W3
W6 = (W5*100)/C1
V4 = W6 / P
V5 = V4 / 3785
P = Density of the solution.
V2 = Volume of the solution in milliliters.
W1 = Weight of the solution in grams.
C2 = Optimum concentration of Sodium Dichromate %w/w.
C1 = Actual Concentration of Sodium Dichromate in %w/w.
W2 = Weight of Sodium Dichromate in solution in grams.
W3 = Optimum weight of Sodium Dichromate in grams.
W5 = Weight of Sodium Dichromate to remove in grams.
W6 = Weight of solution to be removed in grams.
V4 = Volume of solution to be removed in milliliters.
V5 = Volume of solution to be removed in gallons.
and,
SCOPE: To determine the concentration of Nitric Acid in a solution.
EQUIPMENT:
5 mL Pipet
25 mL Buret
250 mL Erlenmeyer Flask
Deionized Water
1.0 N Sodium Hydroxide
100 mL Graduated Cylinder
0.1% Methyl Orange Indicator Solution
PROCEDURE:
Using the pipet, transfer 5 mL of the sample into the Erlenmeyer flask. Using
the graduated cylinder, add 100 mL deionized water to the flask. Add 5-10 drops
of the Methyl Orange indicator to the diluted sample. Titrate with 1.0N sodium
hydroxide. The solution will change colors from orange-red to yellow. Record the
mL used as V1.
CALCULATION:
C1= V1*F1*N1
C1 = Concentration of Nitric acid in %v/v.
V1 = mL of sodium hydroxide used in the titration
F1 = 1.27
N1 = Normality of sodium hydroxide used in the titration.
REPLENISHMENT:
W1= [(C2-C1)*V2] / 100
W1 = Gallons of Nitric acid to add to the tank
C2 = Optimum concentration of Nitric acid in %v/v.
C1 = Concentration of Nitric acid in %v/v.
V2 = Operating volume of tank in gal.
DILUTION:
V3 = [(C1-C2)*V2] / C1
V3 = Gallons of solution to remove from the tank
C2 = Optimum concentration of Nitric acid in %v/v.
C1 = Concentration of Nitric acid in %v/v.
V2 = Operating volume of tank in gal.

Willie Alexander
- Colorado Springs


2006

Thanks for the info, Willie !

John Doyle [returning]
- Springdale, Arkansas


2007

Hi,
On the V2 Calculation under "Replenishment" "V2 = Volume of the solution in milliliters" for the Sodium Dichromate, is that asking total mL. for the Full Tank Volume?

Thanks,

Ron Simpson
- Phoenix, Arizona

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