Chemical Processes Industries Inorganic IICourse # 501

23rd February, 2007

EXPERIMENT # 3

OBJECT

Determination of Zinc as Zinc Pyrophosphate.

REAGENTS

1. Zinc Carbonate Solution.2. 10% Diammonium Hydrogen Phosphate.3. Dilue Ammonia Solution.

REACTIONS

Zn+++HPO4++NH4ZnNH4PO4+H+

2ZnNH4PO4Zn2P2O7+2NH3+H2

OBSERVATION

Weight of the empty crucible = 32.02gm

CALCULATION

Weight of the empty crucible = 32.02gmWeight of the empty crucible + ppt = 32.23gmWeight of ppt (Zn2P2O7) = 32.23-32.02 = 0.21gmMolecular Weight of Zn2P2O7 = 304gmAmount of Zn in Zn2P2O7 = 130gm(0.21)304gm of Zn2P2O7 contains = (130/304)0.21gm of Zinc

= 0.089gm

25ml of Zinc Salt Solution contains = 0.089gm of Zinc1000ml of Zinc Salt Solution contains = (0.089/25)1000gmof Zinc

=3.59gm of Zinc

RESULT

The amount of Zinc is found to be 3.59 gm.

Muhammad Irfan SharifMuhammad Asim IqbalMuhammad Afaq Abbassi

Chemical Processes Industries Inorganic IICourse # 501

DISCUSSION

The object of our experiment is to determine the quantity of Zinc as Zinc Pyrophosphate by gravimetric analysis.

MECHANISM

Mechanism is categorized in the following steps.

1. N eutralization of Zinc carbonate solution

The zinc is precipitated as phosphate from neutralization ,therefore the solution of zinc carbonate (Acidic in nature) must be neutralized with Ammonium Hydroxide (NH4OH) which is basic in nature ,with a neutral solution otherwise the precipitate

are not obtained

2. Boiling of Neutral Solution

By the reaction of Zinc Carbonate and NH4OH (dilute) the formation of soluble complex cations Zn(NH3) is possible which not be formed to avoid this we heat the solution to boiling to remove all ammonia giving a neutral solution with Zn++cation.

.3. Formation of Precipitate of Zn3(PO4)2

After boiling we slowly add diammonium phosphate (NH4)2PO4 to form precipitate

of zinc phosphate (Zn3PO4)2 an Amorphous compound

4. Formation of Zinc Ammonium Phosphate Zn(NH4)PO 4 .H 2 O Crystals

Now this precipitate become crystalline to give Zn(NH4)PO4.H2O crystal by giving a

constant steam heating for about 30 minutes in a water bath .

It is to be noted that crystallization only possible at 60-90oc temperature range which

must be controlled and if the temperature is at 105oC the crystalline product losses its water of crystallization for this type of condition we use steam healing

Zn++ + HPO-4+NH4 ZnNH4PO4 + H+

5. Washing of Crystals

The crystals are washed with Diammonium Hydrogen Phosphate for the removal of chlorides

Muhammad Irfan SharifMuhammad Asim IqbalMuhammad Afaq Abbassi

Chemical Processes Industries Inorganic IICourse # 501

6. Ignition of Crystals

The crystals are then burn in a crucible slowly to remove water of crystallization and then strongly which causes the decomposition of crystals i.e. the pyrolysis process occur and we obtain a compound called “Zinc Pyro Phosphate” the word pyro indicating that this compound is obtained through the pyrolysis process (i.e. decomposition by heating )

2ZnNH4PO4Zn2P2O7 + 2NH3 + H2

REFERENCE

Ferman Inorganic Analysis

Muhammad Irfan SharifMuhammad Asim IqbalMuhammad Afaq Abbassi