Teknologi dan Rekayasa Objectives After this session, the students are expected to be able : 1.to explain the steps of determination of iron and manganese 2.to explain the objectives of every step 3.to explain the function of reagents 4.to conduct the determination of iron and manganese 5.to do the calculation in the determination of iron and manganese 6.to arrange the report of the determination of iron and manganese

Iron in water  Iron in water is in two form: - Fe 2+, ferrous ion, dissolve in water (the water still colorless but has iron smell) - Fe 3+, ferric ion, undissolve in water  causes turbidity in water (dissolve at pH < 5)  In the ground water, iron exists as Fe 2+ and in the surface water in form of Fe 3+  The form of iron (ferrous/ferric) changes caused of iron bactery

High content of iron in water causes : 1.Stain/spot of dirt on clothes, paper and equipment 2. Metalic taste in water 3. Rancid (smell of fish)

Determination of Iron  Iron is determinated as total iron, in form of Fe 3+  The method is constant level coloroimetric (Nessler tube & comparator)  The coloring reagent is KSCN Principle : Iron in water determinated as total iron in form of Fe 3+, Fe 2+ oxidized to Fe 3+, Fe 3+ reacts with KSCN to form complex substance colored yellow to blood red. The color intensity of the sample solution compared to the standard solution Note : if the iron content is high, the appropriate method is titrimetric or gravimetric method

Determination of Iron Preparation of 100 ppm Fe 3+ standard solution (ferric alum) Preparation of 0,1 – 0,5 ppm standard In the Nessler tube Sample preparation : (max. Fe 0,5 ppm) Put 100 mL of sample in to an erlenmeyer flask Add H 2 SO4 + Br 2 then heat until the color of Br 2 dissapears Let it cool and pour in to the Nessler tube Add KSCN to the sample and the standard solution

Calculation (mg Fe /L) Changed level colorimatric method  The same color intensity indicate the same concentration According to Lambert-Beer’s law A 1 = A 2  1.b 1.c 1 =  2.b 2.c 2  1 =  2, so : b 1.c 1 = b 2.c 2 If : 1 standard, 2 sample, : b 1.c 1 c 2 = _________ b 2

Manganese in water  Manganese in water exists in 2 forms : - Mn 2+ dissolved in water (the water still colorless) - Mn 4+ undissolved in water (MnO 2 )  causes turbidity in water  In the ground water, manganese exists as Mn 2+ and in the surface water in form of MnO 2

The high content of manganese causes : 1.Stain/spot of dirt on clothes, paper and equipment 2. Metalic taste in water 3. Rancid (smell of fish) 4. High concentration of manganese is toxic

Determination of Manganese  Manganese is determinated as total manganese, in form of KMnO 4  The method is constant level coloroimetric (Nessler tube & comparator) Principle : Manganese in water oxidized with persulfate in acidic condition to form the reddish purple colored permanganat. The color intensity of the sample solution then compared to the standard solution Reaction : 2Mn S 2 O H 2 O  2MnO SO H +

Determination of Manganese Preparation of 100 ppm KMnO 4 standard solution Preparation of the series 0,1 – 0,5 ppm In the Nessler tube Sample preparation : Put 100 mL of sample in to an erlenmeyer flask Add HNO 3 8N and AgNO 3 5%  filter Heat the filtrate +200 mg of K 2 S 2 O 8, boil for 5 minutes Compare the t he color intensity of the sample solution to the standard solution

Calculation (mg Mn /L) Changed level colorimatric method  The same color intensity indicate the same concentration According to Lambert-Beer’s law A 1 = A 2  1.b 1.c 1 =  2.b 2.c 2  1 =  2, so : b 1.c 1 = b 2.c 2 If : 1 standard, 2 sample, : b 1.c 1 c 2 = b 2