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CHEMISTRY : Qualitative Analysis


Analysis and ID of the "Blue Ink Powder"



PROJECT CODE: 1.01
SECTION: QUALITATIVE ANALYSIS
PROJECT TITLE: Analysis and Identification of the "Blue Ink Powder"
RELEASE DATE: 1st OCTOBER - 9th OCTOBER 1992
LAST UPDATE: 30 August 2009
VERSION HISTORY: 1.0 - 10-Aug-92 = First version
1.1 - 29-Aug-09 = Enhanced and revised text



INTRODUCTION

Long time ago, I have found a tin box with a dark blue powder. Still readable on the can was "ink powder" and it was used to be dissolved in water (or ethanol/water mixture?) to make ink which was then utilised to refill ink cartridges in old-fashioned pens. Qualitative analysis is carried out to determine the chemical constituents of this ink powder

PROCEDURE

Sample Preparation

About 10g of Blue Ink Powder was placed in 50cm of warm (50 C) water and allowed to cool. The solution was filtered and most of the powder remained as residue. The filtrate was just faint blue. Dissolving more powder (50g) in boiling water did not improve the solubility. The powder was hence sparingly soluble in water. Strangely, this should be more readily soluble since it is used as an ink when dissolved in water. Has this old powder been expired ages ago?

Chemical analysis on the Filtrate


Test No. Test Applied Results Conclusion
01 Effect on METHYL ORANGE on solution No colour change Solution is not Acidic
02 Effect on LITMUS POWDER on solution No colour change Solution is not Acidic (confirmed)
03 Effect on ACIFIED METHYL POWDER on solution No colour change Solution is not alkaline
04 Adding CONCENTRATED HCl to solution No effervescence or colour change No alkaline / base products present
05 Adding CONCENTRATED NaOH to solution Solution turned to faint brown colour, but no precipitate was formed Solution is not acidic, contains no Cations of insoluble Hydroxides. Unknown reason for colour change.
06 Adding CONCENTRATED AQUEOUS AMMONIA Solution turned to faint brown colour, but no precipitate was formed Solution is not acidic, contains no metal cations of insoluble Hydroxides. Unknown reason for the given colour change.
07 Dissolve the blue ink powder in CONC. NaOH solution A Green solution (+ some undissolved powder) was produced instead of the usual deep blue colour. After some hours the green solution turned to brown Typical colour change of Iron ions. Iron present as Fe+ (green) turned to Fe+ (brown) by oxidation after some time.
08 Dissolve powder in CONC. AQUEOUS AMMONIA Solution (Nh4OH) A Navy Blue precipitate was formed. On standing a colourless solution and rusty brown precipitate was formed. The precipitate was filtered, collected and tested as indicated in the experiments below The Iron cation is probably present in the Blue Ink Powder.
09 Adding CONC HCl to ppt formed in 08 Some of the residue forming a yellow solution Characteristic of Fe+ Ions
10 Adding SODIUM CARBONATE to the solution formed in 09 Rusty brown ppt. was formed. Typical ppt of Iron (III) Carbonate, hence the yellow solution from 09 contains Iron + ions
11 Addition of the following Cations with the ink powder solution: Cu+, Zn+, Co+, Mg+, Pb+, Ba+, Mn+, Ca+ No colour change or precipitation The fact that no cation gave a positive result shows that iether the powder dissolved is so minute that no results are obtained, or it is a complex salt, which does not form ppt with the tested cations
12 Addition of the following Anions with the blue filtrate: TANNATE, TANNATE, BENZOATE, BORATE, PHOSPHATE, IODIDE, IODATE, PERMANGANATE, THIOSULPHATE, CARBONATE, BROMIDE,SULPHIDE, SULPHATE, CHLORIDE,DICHROMATE. Only the permanganate gave a visible change: It was decolourized slowly. It is possible that a very small amount of reducing agent is present in the solution. The fact that no ppt was formed, makes it seams that there is no free metal ions in solutions, or more probable, they are present in trace amounts.

Conclusions for the tests performed so far
  1. The solution produced by the "blue ink powder" is very dilute.
  2. It is neutral.
  3. Contains a reducing agent effect.
  4. Iron is present propably in the form of a Complex compound.


EFFECTS ON HEATING THE "BLUE INK POWDER"

The powder evolves a white gas which is a mixture of Ammonia (smelt) [*1] and another gas (unknown) having a charring (burning) smell. This gas burned in a red/yellow non-sooty flame [*2]. Some water vapour was given off as it condensed at the upper part of the flask. Some powder burnt with sparkles as it fell in direct in the flame [*4]. The residue left glowed red for some time before cooling down [*5] and was black with some traces of brown.

The residue did not formed a blue solution with water [*6]. On adding HCl to the residue, effervescence took placing (with the yield of Hydrogen) and a brown solution was formed,[*7a]. Half the residue did not react and remained undissolved [*8]. This solution produced a brown precipitate with NaOH [*7b].

Conclusions for this test:
  1. Ammonia is present in the powder.
  2. An organic gas is evolved. It is neither an aromatic compound nor have many carbon atoms (else it would burn with a sooty manner).
  3. Water molecules were released but not sure if as a result of thermal decomposition or simply moisture within the sample.
  4. Characteristic of iron fillings.
  5. Characteristic of Carbon.
  6. Heating decomposed the compound. Hence it is not a simple ionic compound (crystal form).
  7. Iron (7a) and Iron oxide (7b) (which is brown) is present in the residue
  8. Carbon is likely to be the substance left as residue

CONCLUSION

The following atoms/molecules were detected in the BLUE INK POWDER.

  1. [Fe] - detected from test 2.08, 2.09, 2.10
  2. [Carbon] - detected from test 3.8
  3. [Ammonia] - detected by smell in test 3.1

Hence my conclusion are that the "BLUE INK POWDER" consists of a complex salt containing Iron as the transition metal with ligands containing carbon, hence the best guess - (CN) and/or ammonia and water ligands.

Therefore I say that the powder is a complex such as [X+] [Fe(CN)6]- where X+ is iether K+, Na+, or propably NH4+. The ligands may vary from 6 (CN), to a mixture of (CN), (H2O) and (NH3). (eg: X+ [Fe (CN)3 (NH3)2 (H20)]





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