what is the brief Procedures and observations

$($ please$)$

A$.$ The establishment of calibration curve

The colorimetric reagent is prepared by dissolving $5\mathrm{.}0g$ of KSCN in $50mL$ of

deionized water.

Prepare $1000mL0\mathrm{.}1MHN{O}_3$ from $6MHN{O}_3$ and use it to prepare standards and

samples.

Prepare an iron$($III$)$ stock solution of $200ppm$ by dissolving appropriate amount of

iron$($III$)$ nitrate in $30mL0\mathrm{.}1MHN{O}_3$ and then transfer and dilute to $100mL$ using a

volumetric flask.

Then dilute the $200ppm$ stock solution to $20ppm$ iron$($III$)$ solution by pipetting $10mL$

solution to a $100mL$ volumetric flask and dilute to the mark.

The $20ppm$ solution is used to prepare four standards with a concentration range of $2\mathrm{.}0$

$-8\mathrm{.}0m\frac{g}{L}$ using $50mL$ volumetric flasks.

Add $10mL$ of each standard and $5mL.$ KSCN solution to a $25mL$ volumetric flask and

dilute to the mark. The mixture is allowed to stand for $5$ minutes until the color is

stabilized.

A blank is prepared by pipetting $10mL$ of deionized water and mix it with $5mL$ KSCN

using a $25mL$ volumetric flask.

The absorbance of each standard solution is then measured at $477nm$ against the blank.

B$.$ The determination of iron in tablet

Weigh one commercial mineral tablet and crush the tablet with a mortar and pestie.

Weigh $0\mathrm{.}1g$ of the sample by an analytical balance and digest it in $5mL$ conc. nitric

acid in a fume$-$hood.

After digestion, dilute the solution to $30mL$ with deionized water and remove the

insoluble material by filtering the solution into a $100mL$ volumetric flask.

Then pipet $10mL$ of the sample solution to a $100mL$ volumetric flask and dilute to the

mark with $0\mathrm{.}1M$ nitric acid.

$10mL$ of the diluted sample is then mixed with $5mL$ KSCN in a $25mL$ volumetric flask

and dilute to the mark with $0\mathrm{.}1MHN{O}_2.$