University:
Arizona State University
Course:
BIO 130 | Environmental Science
Academic year:

2024
Views:

103

Pages:

2
Author:

Thuyoul US

NITRATE DETERMINATION Basis for Determination N in the form of NH4 and NO3 is dissolved in water, distilled by the addition of alkali. The NH 3 that came out was stored with boric acid and the distillate was titrated with a standard acid solution HCl 0.1 N. The remaining determination of N-NH4 that still contained NO3 was reduced with Devarda metal to NH 4. Distillation is carried out again as in the determination of N-NH4. Equipment 2 decimal precision analytical balance Erlenmeyer pumpkin 250 ml Shake machine at 250 shaking speed-1 min Distillation equipment Boiled pumpkin Digital burette or micro burette Reagents Blend of KCl 1N and HCl 0.1 N HCl 0.1 N Boric acid solution 1 % Weigh 1 g of boric acid, dissolve 100 ml of H2O. Dissolve NaOH 40 % Dissolve 400 g of NaOH in a glass cup with 600 ml of ion-free water, after cooling it is diluted to 11. Conway Indicator Dissolve 0.100 g of metal red and 0.150 g of bromcresol green (Bromcresol Green) with 100 ml of ethanol 96%. Devarda alloy. Boiling stones Made from crushed pumice How it works 1. Carefully weigh 10.00 g of soil sample into 250 ml erlenmeyer. Add a mixture of 1 N KCl and 0.1 N HCl 50 ml. 2. Shake with a whisk machine for 30 minutes at a speed of 200 shakes-1 minute, then filter. 3. Put the filtered extract into the distilled flask, add a little boiling stone and 50 ml of ion-free water. 4. Prepare a destilate container, which is 10 ml of 1% boric acid that has been given three drops of the Conway indicator in Erlenmeyer (red solution). 23 5. Distill the extract by adding 10 ml of 40% NaOH to the boiling flask. Distillation is completed when the distillate in the container has reached the volume 50-75 ml (green solution). 6. The distillate is titrated with a 0.1 N HCl raw acid solution until the titration endpoint changes color from green to pink. 7. Work on the determination of blanks. 8. Extract the former determination of N-NH4 in a boiling flask, plus 50 ml of ionfree water left to cool (if necessary soaked in water). 9. Prepare another distillate reservoir. 10. Distill by adding 2 g of devarda alloy, there will be a boiling by itself (bubbles will arise). 11. The distillation heater is turned on when the bubbles in the boiling flask have run out and Heating is carried out gradually, this is to avoid re-foaming that can enter the destilate reservoir. Distillation is terminated when the volume of distillate in the container has reached 50-75 ml. 12. The distillate is tirated with HCl 0.1 N standard acid as per the determination of N-NH4. Account ml HCl(I) (example-blank) x N HCl x 18 x 1000 NH4 level (ppm) = Bkm ml HCl(II) (example-blank) x N HCl x 62 x 1000 NO3 level (ppm) = Bkm Information: ml HCl(I) = ml titrant of the first example for the determination of NH4 without devarda ml HCl(II) = ml titrant of the second example for the determination of NO3 with devarda BKM = in grams = [100/(100+KA)]; KA = % moisture content 24

Basis for Determination

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