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CHEMISTRY : Pyrotechnics (FireWorks)

Chemical Analysis of Firework Material



PROJECT CODE: 5.01
SECTION: Chemical Analysis of firework material
PROJECT TITLE: Murtal tal-bomba tal-kaxxa nfernali (dawl abjad)
SAMPLE SOURCE: Saint Sebastian, Qormi
RELEASE DATE: 21-23 July 99
LAST UPDATE: 12 September 99
VERSION HISTORY: 1.0, 1.1 ( Context updates)
V1.2 (Text and formatting update - Sep-2009)



Part 1: PHYSICAL APPEARANCE + DIMENSIONS


1.0) Appearance

The material inside the bomb consisted of:
  1. Fine, ash-like, mid-grey powder
  2. Chiseled wood ("wood-chips")
It is assumed that the wood-chips have no explosive function and is added to compensate on the actual gun powder, so making the bomb cheaper to make. Below is the diagram of the appearence, dimensions and composition of a 'tal-kulur' (colour) bomb used in the "kaxxa nfernali" .
Murtal tal-bomba tal-kaxxa infernali


1.1) Seperation of the wood-chips from the powder

wood-chips was seperated from the actual explosive material simply by passing the mixture from an narrow pore "gharbiel" leaving most of the wood-chips above, and the fine powder below. This was repeated for several times to remove as much wood-chips as possible. The poweder was extremely fine, like dust. Further experiments are done on this powder removed from wood-chips

1.2) Proportion of wood-chips to gunpowder

Measurment Sample 1 Sample 2
Wood Chips Gunpowder Wood Chips Gunpowder
Volume (Cm3) 110 90 135 100
Weight (g) 20 65 13 80
From the results, it can be concluded that there is no defenite ratio betwen how much wood-chips and powder is mixed, but there is a tendency that it is mixed approximately by volume in the ratio 1:1 to 5:4 mixture v/v. Propably no measurments are made on mixing these two, and wood-chips is added at quasi random quantities.

Part 2: SOLUBILITY IN WATER

2.0) Method

5.00g were dissolved in about 100ml water pre-warmed at about 70C. in a conical flask. The flask was closed and left overnight for complete dissolving of any soluble substances. The test was formed in duplicates.
The powder is so fine that on adding water, it tend to clump and remains enclosed in a bubble of air. Vigourous shaking is required to free all the powder so that is comes in contact with water. On settling, most of the powder deposits at the bottom of the flask, leaving a colourless solution and some powder floating at the surface.
After leaving for overnight, the mixture is filtered from a filter paper for 3-4 times to obtain the undissolved material as the residue on the filter paper, and the dissolved material in solution as the filtrate.
After washing with water, the undissolved material was dried carefully and weighed.
The filtered solution was evaporated to give white crystals. Since there is the risk that over evaporation may cause thermal decomposition of the solid, the solution was evaporated to 25mls hence making a concentrated sol.

2.1) Ratio of Soluble to Unsoluble Components

Test 1
  1. Mass of powder: 5.00g
  2. Mass of filter paper: 0.75g
  3. Mass of dried powder + filter paper: 3.09g (4.76 -> 3.59 -> 3.46 -> 3.28 -> 3.09g)
  4. Mass of dried powder: 3.09g - 0.75g = 2.34g

Test 2
  1. Mass of powder: 5.00g
  2. Mass of filter paper: 0.77g
  3. Mass of dried powder + filter paper: 3.12g (4.65, 3.55, 3.42, 3.30, 3.12g)
  4. Mass of dried powder: 3.12g - 0.77g = 2.35g

Test 3
  1. Mass of powder: 10.00g
  2. Mass of filter paper: 0.77g
  3. Mass of dried powder + filter paper: 5.18g (8.51, 6.77, 6.34, 5.68, 5.49, 5.22g)
  4. Mass of dried powder: 5.22g - 0.77g = 4.45g

Test 4
  1. Mass of powder: 5.00g
  2. Mass of filter paper: 0.77g
  3. Mass of dried powder + filter paper: 3.00g
  4. Mass of dried powder: 3.00g - 0.77g = 2.23g

The powder may include some traces of water moisture since complete dryness may not have been achieved. However, the powder was well dry, and so the moisture mass may be considered negligible.

The mass of Soluble substances is simply calculated by:

Mass of Soluble solids = (Mass of mixture) - (Mass of undissolved solids)


  1. Test 1 - 5.00g - 2.34g = 2.65g
  2. Test 2 - 5.00g - 2.36g = 2.66g
  3. Test 3 - 10.00g - 4.45g = 5.55g
  4. Test 4 - 5.00g - 2.23g = 2.77g

2.2) Summary of Results:

TEST Weight of
Sample Mixture (g)
Weight of
Unsoluble Solid (g)
Percentage Weight of
Soluble Solid (g)
Percentage
TEST 1 5.00 2.34 47% 2.66 53%
TEST 2 5.00 2.35 47% 2.65 53%
TEST 3 10.00 4.45 45% 5.55 55%
TEST 4 5.00 2.23 45% 2.77 55%
Further tests are now performed both on the dissolved portion and on the undissolved portion (not on the entire powder mixture)

Part 3: ANALYSIS OF THE DISSOLVED PORTION

3.0) Crystallogy

Crystal_Structure1.jpg - 3214 Bytes
A supersaturated solution was performed and cooled slowly to form large crystalls. Some of the sol was cooled and evaporated on a microscope slide and the crystals formed were studied.

The crystal of this analyte are FLAT and TRAPEZIUM in shape. No needles or branching was observed, and there were some varients of the shape such as triangles, or asymetrical shapes. The most seen shape was that of a flat parallelogram trapezium, not rhombic by little.

This shape is quite different from potassium nitrate (needle branching crystals) and from Potassium perchlorate (small, cubic symettry, 3D crystals)

3.1) Test for nitrate ring

To eliminate the chance that the chemical is potassium nitrate (much used in pyrotechnix) a nitrate test was carried out (together with a control). There was no brown ring formed, but instead the sulphuric acid layer turned orange brown in colour. Possiblly an Oxy-Chloride (chlorate or perchlorate) ?? On adding conc sulphuric acid a certain smell like of chlorine was detected

3.2) Ammonium detection test

To some mls of the solution, few drops of conc Sodium Hydroxide was added and heated till boiling. No ammonia gas was evolved, hence the dissolved substance is not an Ammonium salt.

3.3) Flame test

A lilac flame was given off on burning some of the solution in a blue flame. This concludes that the cation is POTASSIUM

3.4) Reaction with different metal salts

The solution was added with the following metal salts to identify it from the pattern of a reactions obtained:

Fe(II), Fe(III), Al, Ba, Co, Zn, Cu, Pb, Sb, Sn.

Strangely enough, no reaction or precipitate was formed with any of these metal salts. (just a faint ppt with Zn which is neglected due being very minute). This is typical for the nitrate, but this has to be excluded since it didn't formed a brown ring with the nitrate test (3.1), and has very different crystal morphology (3.0).

3.5) Reaction with strong acids

Few crystals under test were placed in 3 clean dry test tubes, and in each tube, few drops of the concentrated acids shown in the table below were carefully added. Results also shown in the table.
Nitric Acid Sulphuric Acid Hydrochloric Acid
On adding nitric acid, there was no effervescence, or heat given off, but the colour changed to yellow and chlorine could be detected - not as strong as in the other acids. On adding sulphuric acid, there was a crackling reaction. On adding few drops more, there was effervescence, and heat while the viscous solution turned brown yellow, and a green gas - Chlorine - was evolved. On adding hydrochloric acid, there was no explosive reaction, but there was effervescence, and the colour turned yellow-green with the production of chlorine.

These tests confirms that the salt is an OXY CHLORIDE, which could be any of the following chlorates:
  1. Chlorate (I) - Hypochlorite, [OCl]
  2. Chlorate (III) - Chlorite, [ClO2]
  3. Chlorate (V) - Chlorate, [ClO3]
  4. Chlorate (VII) - Perchlorate. [ClO4]
The perchlorate is excluded since it gave no reaction on adding conc acids, and also it has a different crystal morphology. I do not have the other chlorate salts to confirm and compare, but it is very propable that the salt involved is POTASSIUM CHLORATE.

Part4: ANALYSIS ON THE UNDISSOLVED PORTION IN HCL


4.0) Method

0.25g of the undissolved part of the powder where reacted with 6 different solutions of hydrochloric acid of different concentrations, as shown:
Solution Concentration Method of Preparation)
Sol A 100% H Cl 4.0 mls conc HCl
Sol B 50% H Cl 2.0 mls conc HCl + 2mls water
Sol C 25% H Cl 1.0 mls conc HCl + 3mls water
Sol D 10% H Cl 0.8 mls conc HCl + 7.2mls water
Sol E 5% H Cl 4.0 mls of the above solution + 4mls water (*)
Sol F 2.5% H Cl 4.0 mls of the above solution + 4mls water (*)
(*) = serial dilution

4.1) Qualitative results of the reaction in HCl

On addition of the various concentrations of H Cl, the following changes were observed:

Sol A:
  1. Reaction was complete after 10mins
  2. Supernatant: beer brown solution
  3. Deposit: 3 layers:
    1. top - brown
    2. middle - mid brown/yellow (mixture?)
    3. bottom - yellow sulphur
Sol B:
  1. Reaction was complete after 30mins approx
  2. Supernatant: pale yellow solution
  3. Deposit: 2 layers:
    1. top - brown
    2. bottom - yellow sulphur
Sol C:
  1. Reaction was complete after overnight (8 hours)
  2. Supernatant: colourless solution
  3. Deposit: 2 layers as in Sol. B:

Sol D:
  1. Reaction was complete after 24hrs approx
  2. Supernatant: colourless solution
  3. Deposit: 2 layers as in Sol. B:

Sol E:
  1. Reaction was complete after 2 days (48 hours)
  2. Supernatant: colourless solution
  3. Deposit: 2 layers as in Sol. B:

Sol F:
  1. Reaction was nearly complete after more than 2 days (> 48hours>
  2. Supernatant: colourless solution
  3. Deposit: as B with very few unreacted greyish powder

In all reactions there was smell of Hydrogen sulphide given off, and this gas was confirmed by the browning of a piece of Lead acetate paper. This seems to be produced by the 10%, 25% and 5% solutions.

4.2) The unreacted deposit

This consisted of a deposit of about 2mm thickness, of which the upper half was brownish and the lower one was fine, granular and yellow in colour. It is likely that the bottom layer consists of Sulphur, while the upper layer being pices of fine ground wood (wood-chips). This is so because the upper layer is not granular, but enlongated like, and sinks slowly.

4.3) Quantitative results of the reaction in HCL

The deposit was filtered from the dissolved portion, washed with cold and warm water, dried completely and weighed with the filter paper. The resulting mass is subtracted by the mass of the filter paper to give the mass of the deposit. With this, one can also calculate how much reacted solid there was in the mixture.
Results:

Sol. A:
  1. Mass of filter paper = 0.39g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.56g
  4. Mass of unreacted deposit = 0.56 - 0.39 = 0.17g
  5. Mass of reacted solid = 0.25 - 0.17 = 0.08g

Sol. B:
  1. Mass of filter paper = 0.35g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.52g
  4. Mass of unreacted deposit = 0.52 - 0.35 = 0.17g
  5. Mass of reacted solid = 0.25 - 0.17 = 0.08g

Sol. C:
  1. Mass of filter paper = 0.37g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.55g
  4. Mass of unreacted deposit = 0.55 - 0.37 = 0.18g
  5. Mass of reacted solid = 0.25 - 0.18 = 0.07g

Sol. D:
  1. Mass of filter paper = 0.37g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.55g
  4. Mass of unreacted deposit = 0.55 - 0.37 = 0.18g
  5. Mass of reacted solid = 0.25 - 0.18 = 0.07g

Sol. E:
  1. Mass of filter paper = 0.38g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.56g
  4. Mass of unreacted deposit = 0.56 - 0.38 = 0.18g
  5. Mass of reacted solid = 0.25 - 0.18 = 0.07g

Sol. F:
  1. Mass of filter paper = 0.38g
  2. Mass of mixture = 0.25g
  3. Mass of filter paper + dried deposit = 0.59g
  4. Mass of unreacted deposit = 0.59 - 0.38 = 0.21g
  5. Mass of reacted solid = 0.25 - 0.21 = 0.04g

As a control, 0.25g of pure sulphur was mixed in water, filtered dried and weighed, hence to serve as a control that no sulphur is lost during drying. In fact 0.25g were obtained again. In the 2.5% solution (F) it appears that there have not been complete reaction, and some unreacted sample was left in the deposit, hence its larger mass compared with the other results.

4.4) Confirmatory quantitative tests

To confirm the above results, 0.65g of sample was completely dissolved in 20mls of 10% HCl (2.0mls Hcl + 18mls water). The deposit was as above filtered, washed dried and weighed. X:
  1. Mass of filter paper = 0.77g
  2. Mass of mixture = 0.65g
  3. Mass of filter paper + dried deposit = 1.28g
  4. Mass of unreacted deposit = 1.28 - 0.77 = 0.50g
  5. Mass of reacted solid = 0.65 - 0.50 = 0.15g


Similarly, another test using 2.00g mixture was peformed and gave the following results: Y:
  1. Mass of filter paper = 0.77g
  2. Mass of mixture = 2.00g
  3. Mass of filter paper + dried deposit = 2.24g
  4. Mass of unreacted deposit = 2.24 - 0.78 = 1.46g
  5. Mass of reacted solid = 2.00 - 1.46 = 0.54g

4.5) Summary of quantitative results

Sample Mixture
Weight (g)
Reacted solid
Weight (g)
Percentage Unreacted deposit
Weight (g)
Percentage
A+B 0.25 0.08 32% 0.17 68%
C+D+E 0.25 0.07 28% 0.18g 72%
X 0.65g 0.15g 23% 0.50g 77%
Y 2.00g 0.54g 27% 1.46g 73%
* Since there is little weight of reacted solid (0.07g) the result is subjective to great errors (+/-0.01g = 4%).

The final average result is of weight of metal in the undissolved part is taken to be 25%, and of the whole mixture as 10%-12%

Part 5: ANALYSIS ON THE SOLID REACTED IN ACID

The filtered solution was added sodium carbonate to neutralize any xs Hcl present. The endpoint is roughly found either on the formation of turbidity (by unsoluble carbonate) or by means of a PH indicator paper (pH4-7). The solution was filtered again from turbidity to obtain a clear solution. This was reacted qualitatively with the following reagents, and their correspond reactions are as shown. A negative control, using dilute Hydrochloric acid solution, was also run with each test.

01: Sodium Hydroxide

Faint white ppt was formed which dissolved on adding xs into a colourless sol. AL, Pb, Zn, Sb, Sn are all possible

02: Ammonia solution

Gelatinous white ppt which is insoluble in xs Zn is excluded, since it is sol in xs)

03: Sodium Carbonate

White ppt

04: Potassium Ferrocyanide (II)

Blue solution (with presence of HCl) Typical of Aluminium

05: Potassium Ferricyanide (III)

Dark green solution, turning to blue on standing Typical of Iron!

06: Potassium Tungstate

White ppt

07: Ammonium MolyBdate

Faint apple green solution ?? unknown reaction - no reaction with an aluminium solution or -ve control

08: Sodium Biselenite

No reaction, but a white ppt was formed with a neutralized (acid free) solution of the sample. No reaction with -ve control or aluminium sulphate solution Formation of the white ppt is unknown??

09: Potassiom Thiocyanate

No reaction - or faint pink solution this is due to presence of Acid (confirmed by negative control)

10: Potassium Vanadate

No reactiion - yellow solution and red deposit is formed by the presence of acid (shown in the -ve control)

11: Sodium Sulphide

A white/faint yellow ppt due to deposition of sulphir is first noticed (also shown in -ve control). In a nearly neutralized solution of the sample, addition of Sulphide formed a gelatinous colourless/grey ppt with a little tinge of green. On adding xs sulphide, the solution dissolved leaving a dirty green sol/fine deposit. Similar reaction with aluminium sulphate sol.

12: Sodium Benzoate

No reaction

13: Sodium Sulphite

No reaction

14: Sodium Thiosulphate

No reaction - Precipitation of sulphur is due to the action of a mineral acid 9as in -ve control)

15: Potassium Iodate

No reaction,but a white ppt was formed with Aluminim sulphate solution???

16: Sodium Borate

Gelatinous white ppt

17: Sodium Phosphate

Gelatinous white ppt
The above results concludes that the metal mainly consists of ALUMINIUM with traces of iron (propably unwanted). However one must consider some reactions which were not the same as when an a known aluminium salt was used, hence:
  1. the formation of a pale green solution with Ammonium Molybdate
  2. the lack of formation of a white ppt wiwth Iodate

Part 6: TESTS ON THE SOLID WHICH DID NOT REACTED IN ACID

6.0) Burning of the solid

On studying visually, the solid consists of a mixture of a fine yellow powder and small pieces, light brown in colour. On burning the mixture in air, the powder melted and then burned in a blue flame giving the smell of Sulphur Dioxide and left behind a black powder of charcoal (carbon).

This test is enough to confirm the presence of:
  1. SULPHUR (The yellow powder)
  2. SMALL PIECES OF WOOD (wood-chips) which became charcoal on burning

6.1) Quantitative results on the sulphur and wood-chips

Sulphur was seperated from wood-chips by means of Chloroform or Carbon TetreChloride which dissolves sulphur in the following ratio:
Weight of Sulphur dissolved in 10ml Cold Chloroform 0.18g / 10ml
Weight of Sulphur dissolved in 10ml Hot Chloroform 0.48g / 10ml)
Weight of Sulphur dissolved in 10ml Cold Carbon TetraChloride 0.09g / 10ml
Weight of Sulphur dissolved in 10ml Hot Carbon TetraChloride approx 0.34g / 10ml

Chloroform was used since it is a better solvent

1.41g of Sulphur + wood mixture dissolved 0.88g of sulphur and left behind 0.46g of wood.

7: SUMMARY OF RESULTS

Thus the part of gunpowder which did not dissolved in water consisted of:
Mixture (Sample) Metal Sulphur Wood error loss %
Weight (g) 2.00 0.54 0.88 0.46 0.12
Percent % (100%) 27% 44% 23% 6%
Rounded Percent % (100%) 25% 45% 25% 5%






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