Gravimetric Analysis Of Nickel Using Dimethylglyoxime Calculation

Professional Quantitative Analytical Tool for Laboratory Precision

What is Gravimetric Analysis of Nickel Using Dimethylglyoxime Calculation?

The gravimetric analysis of nickel using dimethylglyoxime calculation is a fundamental technique in analytical chemistry used to quantify the concentration of nickel in a solution. This method relies on the formation of a brilliant red, insoluble complex known as nickel dimethylglyoximate [Ni(C₄H₇N₂O₂)₂] when dimethylglyoxime (DMG) is added to an ammoniacal solution of nickel salts.

Laboratory technicians and chemistry students utilize this gravimetric analysis of nickel using dimethylglyoxime calculation because it is highly selective. Dimethylglyoxime acts as a chelating agent that specifically binds to nickel ions under controlled pH conditions (usually pH 8-9). This specificity ensures that other metal ions do not interfere with the final results, making it a gold standard in mineralogy and metallurgy.

A common misconception is that the precipitate can be weighed immediately. In reality, the gravimetric analysis of nickel using dimethylglyoxime calculation requires meticulous drying of the precipitate at 110-120°C to ensure all moisture is removed before the final mass is recorded. Failure to do so leads to significant errors in the calculated percentage of nickel.

Gravimetric Analysis of Nickel Using Dimethylglyoxime Calculation Formula

To perform the gravimetric analysis of nickel using dimethylglyoxime calculation, you must understand the stoichiometric relationship between the nickel ion and the DMG complex. One mole of nickel reacts with two moles of dimethylglyoxime.

The mathematical derivation is as follows:

1. Calculate the mass of the precipitate: Precipitate Mass = (Weight of Full Crucible – Weight of Empty Crucible)
2. Apply the Gravimetric Factor (GF): The ratio of the atomic weight of Nickel (58.6934) to the molecular weight of the complex (288.91).
3. Calculate the Mass of Nickel: Mass Ni = Precipitate Mass × 0.2032
4. Find the percentage: % Ni = (Mass Ni / Sample Weight) × 100

Variable	Meaning	Unit	Typical Range
Wsample	Initial sample mass	Grams (g)	0.1 – 1.0 g
Wppt	Mass of Ni(DMG)₂	Grams (g)	0.05 – 0.5 g
GF	Gravimetric Factor	Ratio	0.2031 – 0.2033
% Ni	Final Nickel Purity	Percentage	0.1% – 99.9%

Practical Examples (Real-World Use Cases)

Example 1: Stainless Steel Sample

Suppose a chemist takes a 0.4500g sample of stainless steel. After performing the gravimetric analysis of nickel using dimethylglyoxime calculation, the empty crucible weighed 28.1200g and the final weight with precipitate was 28.3150g.

• Precipitate Weight: 28.3150 – 28.1200 = 0.1950 g
• Nickel Weight: 0.1950 × 0.2032 = 0.0396 g
• Result: (0.0396 / 0.4500) × 100 = 8.80% Ni.

Example 2: Nickel Ore Analysis

In a mining lab, 1.2000g of ore is processed. The resulting red precipitate weighs 0.5500g. Using the gravimetric analysis of nickel using dimethylglyoxime calculation:

• Nickel Weight: 0.5500 × 0.2032 = 0.11176 g
• Result: (0.11176 / 1.2000) × 100 = 9.31% Ni.

How to Use This Gravimetric Analysis of Nickel Using Dimethylglyoxime Calculator

Our digital tool simplifies the complex chemistry math. Follow these steps:

• Step 1: Enter the initial “Weight of Sample”. Ensure your scale is calibrated to at least 4 decimal places.
• Step 2: Input the weight of your “Empty Crucible” (sintered glass).
• Step 3: Input the “Weight of Crucible + Precipitate” after drying to constant mass.
• Step 4: The tool automatically processes the gravimetric analysis of nickel using dimethylglyoxime calculation in real-time.
• Step 5: Use the “Copy Results” button to transfer your data to a lab report.

Key Factors That Affect Gravimetric Analysis of Nickel Using Dimethylglyoxime Calculation

Performing an accurate gravimetric analysis of nickel using dimethylglyoxime calculation requires control over several experimental variables:

• pH Control: The solution must be slightly ammoniacal (alkaline). If it is too acidic, the complex will not precipitate.
• Excess Reagent: While DMG is needed, an excessive excess of dimethylglyoxime can cause it to precipitate out itself, leading to a higher mass and inaccurate gravimetric analysis of nickel using dimethylglyoxime calculation results.
• Interfering Ions: Elements like Cobalt or Iron can interfere if not masked. Iron is typically masked using tartaric or citric acid.
• Temperature: Precipitation should occur in a hot solution (around 80°C) to promote the growth of larger, easily filterable crystals.
• Solubility: Nickel dimethylglyoximate is slightly soluble in alcohol (the solvent for DMG), so avoid adding too much reagent.
• Drying Temperature: The precipitate must be dried at 110-120°C. High temperatures (>140°C) can cause sublimation of the complex, ruining the gravimetric analysis of nickel using dimethylglyoxime calculation.

Frequently Asked Questions (FAQ)

1. Why is dimethylglyoxime used for nickel?

It forms a highly stable, specific red chelate with Ni²⁺ that is virtually insoluble in water, allowing for precise gravimetric analysis of nickel using dimethylglyoxime calculation.

2. What is the color of the precipitate?

The precipitate is a characteristic bright strawberry red.

3. Can I use this for Cobalt analysis?

While DMG reacts with Cobalt, the complex is soluble; therefore, it does not work for standard gravimetry.

4. What is the significance of the 0.2032 factor?

This is the gravimetric factor representing the mass of Nickel in one gram of the Ni(DMG)₂ complex.

5. Why do we add ammonia?

Ammonia ensures the pH is alkaline (8-9), which is necessary for the quantitative precipitation of the nickel complex.

6. How many times should I dry the crucible?

Until “constant mass” is reached, meaning successive weighings differ by less than 0.0002g.

7. Does the precipitate contain water of hydration?

No, the Ni(DMG)₂ complex is anhydrous, which simplifies the gravimetric analysis of nickel using dimethylglyoxime calculation.

8. What happens if I use too much alcohol?

Excess alcohol can increase the solubility of the precipitate, leading to negative errors in your analysis.