“DETERMINATION OF LEVEL OF TOXICITY IN DIFFERENT BRAND OF LATEX (WATER) BASED PAINT”

ABSTRACT

All people around the world have been using paint in their household but they have no idea that all this time they have been exposed to toxic substances that can be found in the paint. Paint manufacturer have used heavy metals substances in making paint pigments which gives variety of colour in paint. The paint pigments are made by using many different types of heavy metals substances which are highly concentrated even in one drop of the paint. For example, yellow and red paint pigments are commonly made of cadmium, Cd. Besides, mercury, Hg, is used in making black pigments in black paint while lead, Pb, is the main chemical suctances in making white pigments in paint. Other than that, cobalt, Co, is readily used in making yellow pigments of paint.

In this experiment, a research has been done to investigate the level of these heavy metals present in their respective paint of two different brands of paint, NIPPON and JOHTUN paint. At the end of the experiment, a conclusion has been made which shows that both paints contain high percentage of heavy metal ions (toxicity) where both paint have percentage exceeds 100% of heavy metals ions present in a single drop of paint sample. This shows both paints should be avoided at all costs to prevent further exposure to these chemical substances which may harmful to human's health. However, NIPPON paint has higher level of toxicity level than JOHTUN paint which makes NIPPON paint is more dangerous than JOHTUN paint.

1. INTRODUCTION

The usage of paint is widely used in decorating houses, mostly applied on walls and fences. This is because paint would give ‘life' to houses as it would appear beautifully when the right colour are been applied. However, people often consider that by applying any types of paint would be enough as long as their choice of colour is applied. What they do not know is that there are types of paint that can only be applied to certain object based on what they are made of. Besides, there are also types of paints that would affect human's health as some of them are made by using chemicals that are toxic.

The toxicity may presence in small quantities in the paint. However, it is may enough to emit fumes that could cause nausea, headaches, dizziness and fatigue if is breathe in for a long time without good circulation of air. Even if breathing in fumes from small cans of paint spray, it may lead to non-reversible brain damage.

1.1 LATEX PAINT

Latex paint or best known as water based paint is one type of paint that is made up of 50% to 90% of water. Although the paint are named ‘latex', however this type of paint most of them does not have natural latex in modern painting. However, nowadays, companies usually refer latex paint as water based paint. This is because, many paints made up today are made with water as the thinner but with resins that are not latex. That is why it is called with term as “water-thinned” or “water-reducible”. Besides, if the paint called latex, it is because they contain plastic resin made of acrylics or polyvinyl.

In modern days, paint comes with lots of types of colours. It is thanks to pigments that give out colour to the paint. Different pigment give out different types of colour and these pigments also are made up of chemicals. Usually common pigment types include mineral salts are which are used both in latex and oil based paint. For example, white colour usually are made up of basic lead carbonate, Pb2(CO3) while many of the red and yellow paints are made up of cadmium.

Although usually the pigment are often the same both in latex and oil-based paint, it is the carriers and binders that differentiate the latex paint to oil-based paint which both will have different characteristics. The carrier is one part of the paint that volatile which will evaporates once the paint is applied on surface. The carrier is also the one which keeps the pigment and the binders together in suspension until the time when the paint is applied to a surface of wall or paper.

The binders; however is the body of the paint, which is the permanent part of the paint. The binder is the one which remains when the paint dries. Besides, it also helps the paint to adhere more to a surface. In latex paint, water-soluble binders will include combination of binder (sometimes acrylic, vinyl, PVA and others), filler, pigment and water. That is why the best latex (water based paints) will be made up of 100% acrylic completely or vinyl acrylics and polyvinyl acetates.

1.2 AIM OR SIGNIFICANCE OF THE STUDIES

There are many types of latex paint with different brand available in the market and lots of people bought every single one of them based on the brands and the price. However, the brand of the latex paint does not ensure it contains higher percentage of toxicity than other brand based on the pigments made to make the paint. So, by doing this experiment, we can determined the total percentage of toxic substance present in a can of paint. As a result, people would know which brand are best to buy and use in order to take care of their health as they will be expose and smell the paint for a long time. This is because when people are expose to the paint, the toxicity would get into the body system trough smell. The toxic are dissolves in the paint and will be vaporize together with them. The toxic is then travel trough the thin air and sucked in by our respiratory system. Once the toxic are in the body, slowly they may affect body system. The effect does not shows any sign in a short period of time, but once it kept accumulated in the body system it will do serious damage to our body such as skin irritation, headaches, nausea, diarrheal and if the nervous system got affected, people may fall into a coma.

1.3 RESEARCH QUESTION

The substance causes paints to be toxic are because of the pigment of paint that give colour is made up of large composition of heavy metals substances. Therefore, research question is made which is “Does level of toxicity is different in different brand of Latex (water) based paint?” So, in order to answer the question above, experiments will be done to find out the level of toxicity in different brand of Latex (water) based paint.

2. HYPOTHESIS

The determination of level of toxicity in paints is determined by the formation of precipitate at the end of the experiments. So, hypothesis is made which “the level of toxicity in paint higher when the mass of precipitate formed increases”. This is because the heavy metal ion in paint will react with chemical reagents to formed insoluble precipitate. If the presence of the heavy metal ion is high in one paint, then the more precipitate will be formed at the end of the experiment, thus higher the level of its toxicity.

3. VARIABLES
3.1 Independent Variable
3.1.1 Paint's Samples

Two different brands of latex paint are used to be tested as samples for this experiment. The brands are Nippon paints and Johtun paints. Both samples will be compared to each other in which whether one brands contain higher toxic substance than the other in order to make the pigment of the paints.

3.1.2 Paint's Colour

Five different colours from each brand are selected to be tested in this experiment. The five colours are red, yellow, white, green and black. The purpose of using different colour for each brand is because the pigments which giving the colour of the paints are made up of different toxic substances. They are:-

* Red pigments in red paints are commonly contains cadmium and lead

* Many of the yellow pigments in yellow paints are made up of cadmium and cobalt.

* The black pigments on the other hand are commonly made up of vermillion which contain mercury

* Almost all green pigments in green paints are made up of cobalt

* Most of the white pigments in the white paints are made up of lead carbonate.

The toxic substances present in the five different colour of paint could then be determine by using confirmatory test for each of them and compared with the same colour of the other brand.

3.2 Dependent variable
3.2.1 The changes in colour

There were four different experiments to indicate the presence of four different substances that considered as toxic. Every each of the experiment would result to changes in colour at the end of the experiment, if the toxic substances are present. So, the changes in colour of the mixture of chemical substances at the end of every experiment would be the dependent variable. The changes in colour were observed by using a piece of white A4 paper as the background so that the changes in colour would be clearly indicated.

3.2.2 The mass of precipitate formed

At the end of every experiment, if the toxic substances are present, not only there would be changes in colour, precipitate would also be formed. The toxic substances ions would react with the reagent used to form precipitate which is insoluble in water. The precipitate would be filtered and its mass would be measured by using an electronic balance. If the mass of the precipitate is high, then it shows that the level of the required toxic substances used to make the pigment of the paint is high too.

3.3 Constant variables
3.3.1 The volume of paint used in the experiment

The intensity of the colour of the paint used in the experiment was very high. So, in order to observe colour changes and precipitate formed, the paint must be diluted with water. This is to ensure that the paint must be clear enough so that any visible changes would be easily indicated.

Therefore, only one drop of paint is used for every trial.

3.3.2 The volume of water used to dilute the paint

The volume of water used for dilute the paint for every trial in each of the experiment is fixed to 10 ml.

4. MATERIALS AND APPARATUS
4.1 Materials

Materials

Quantity

Nippon's paint and Johtun's paint colour blue, yellow, red, black, and green.

1 drop

6.0 mol of Ammonia,NH3

20 ml

6.0 mol of Hydrochloric acid, HCl

20 ml

Thioacetamide

15 ml

12.0 mol of Hydrochloric acid, HCl

15 ml

6.0 mol of Nitric acid, HNO3

15 ml

Potassium Chromate, K2CrO4

10 ml

0.5 mol of Potassium Thiocyanate, KCSN

10 ml

Acetone

10 ml

Table 1 List of materials

4.2 Apparatus

Apparatus

Quantity

Test tubes

40

5 ml measuring cylinder

2

50 ml measuring cylinder

2

Electronic balance

1

Dropper

10

A4 paper

1

50 ml beaker

8

Test tube holder

1

Filter paper

40

Filter funnel

1

Table 2 List of apparatus

5. METHODOLOGY
5.1 Sample Preparation

The colour intensity paint samples for this experiment were very concentrated when the paints were bought from the shop. In order for this experiment to work, the paint need to be dilute first to form faint colour so that after the confirmatory test will be done, if there is any changes to the colour, it would be clearly observed. So, only drop of each paint sample with different colour was taken and been put into the test tube. Then, 10 ml of distilled water was measured using a measuring cylinder and been poured into each test tube containing the paint sample prepared earlier. Then, very faint colour were formed for every paint samples and readied for the confirmatory test.

5.2 Confirmatory Test

A) CONFIRMATORY TEST FOR CADMIUM ( Cd 2+) [1]

1- Add 1 drops of red paint sample into a test tube.

2- Then, add 6 M NH3 (aq) until the solution become neutral.

3- Make the solution acidic by adding one or more drops of 6 M HCl.

4- After that, add 1 ml of thioacetamide and stir well.

5- Heat the test tube in the boiling water bath for 5 minutes.

6- If cadmium is present, a yellow precipitate of cadmium sulphide should form.

7- Steps 1 to 7 are repeated using yellow, white, green and black colour paint.

B) CONFIRMATORY TEST FOR MERCURY (II), (Hg2+) [2]

1- If the results in procedures in A; get black precipitate at the end of the experiment, then, mercury is present.

2- For further confirmation, try to dissolve the precipitate in 1 ml of 12 M HCl with heating.

3- If it does not dissolve in HCl, try the same procedure with 1 ml of 6 M (dilute) HNO3.

4- If it still does not dissolve, then try to dissolve it in a mixture of 1 ml of 6 M HCl and 1 ml of 6 M HNO3, heating for 2 minutes in a water bath. Most of the black precipitate should dissolve because mercury(II) sulphide is the least soluble of the metal sulphides.

C) CONFIRMSTORY TEST FOR LEAD (Pb2+) [3]

1- Add 2 drops of dilute hydrochloric acid to 5 drops of the original red paint sample. A white precipitate identifies Ag+ or Pb2+.

3- Then, add 2 to 5 drops of K2CrO4 solution to 5 drops of the original solution. A red precipitate identifies Ag+. A yellow precipitate identifies Pb2+.

D) CONFIRMATORY TEST FOR COBALT COMPOUNDS ( Co2+) [4]

1- Add 1 drops of red oil based paint into a test tube.

2- Add 5 drops of 0.5 M KNCS and mix together.

3- Add an equal volume of acetone and mix. A blue colour indicates the formation of [Co(NCS)4]2-

5.3 Measurements on mass of the precipitate formed

When there are any changes of color of each experiments, precipitate would formed indicating that the toxic substances are present. Then, the precipitate would be filtered by using a filter funnel. The precipitate is then would be dried first to prevent any presence of water that may affect the measurements of mass of the precipitate. The mass of the precipitate is measured by using an electronic balance.

6. DATA COLLECTION
6.1 Results

Below are the results of data obtained at the end of the experiment based on qualitative on two different brand.

A) JOHTUN PAINT

Confirmatory test

Color

Changes of color of the solution

Presence of precipitate

Initial

Final

Cadmium

Red

Faint red

Slightly colorless

Yellow precipitate in very small amount

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

Slightly colorless

Yellow precipitate in very small amount

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Mercury

Red

Faint red

No change

No, red sediment present

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

No change

No, yellow sediment present

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Lead

Red

Orange + red

No change

No, red sediment present

Black

Orange + black

No change

No, black sediment present

Yellow

Orange yellowish

No change

No, yellow sediment present

Green

Greenish orange

Clear green

Yellow precipitate in very small amount

White

Orange + white

Slightly colorless

Yellow precipitate in very small amount

Cobalt compound

Red

Faint red

No change

No, red sediment present

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

Solution turns slightly blue

No, little yellow sediment present

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Below are results of data collected quantitatively

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cadmium

Red

Yellow precipitate in very small amount

0.02

Black

No, black sediment present

-

Yellow

Yellow precipitate in very small amount

0.01

Green

No, green sediment present

-

White

No, white sediment present

-

Mercury

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

No, green sediment present

-

White

No, white sediment present

-

Lead

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

Yellow precipitate in very small amount

0.02

White

Yellow precipitate in very small amount

0.04

Cobalt compound

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, but solution turns to slightly blue

-

Green

No, green sediment present

-

White

No, white sediment present

-

Table 4 Quantitative data for JOHTUN paint

B) NIPPON PAINT

Confirmatory test

Color

Changes of color of the solution

Presence of precipitate

Initial

Final

Cadmium

Red

Faint red

Slightly colorless

Yellow precipitate in very small amount

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

Slightly colorless

Yellow precipitate in very small amount

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Mercury

Red

Faint red

No change

No, red sediment present

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

No change

No, yellow sediment present

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Lead

Red

Orange + red

No change

No, red sediment present

Black

Orange + black

No change

No, black sediment present

Yellow

Orange yellowish

No change

No, yellow sediment present

Green

Greenish orange

Clear green

Yellow precipitate in very small amount

White

Orange + white

Slightly colorless

Yellow precipitate in very small amount

Cobalt compound

Red

Faint red

No change

No, red sediment present

Black

Faint black

No change

No, black sediment present

Yellow

Faint yellow

Solution turns slightly blue

No, little yellow sediment present

Green

Faint green

No change

No, green sediment present

White

Faint white

No change

No, white sediment present

Table 5 Qualitative data for NIPPON paint

Below are results of data collected quantitatively

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cadmium

Red

Yellow precipitate in very small amount

0.03

Black

No, black sediment present

-

Yellow

Yellow precipitate in very small amount

0.01

Green

No, green sediment present

-

White

No, white sediment present

-

Mercury

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

No, green sediment present

-

White

No, white sediment present

-

Lead

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

Yellow precipitate in very small amount

0.01

White

Yellow precipitate in very small amount

0.02

Cobalt compound

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, but solution turns to slightly blue

-

Green

No, green sediment present

-

White

No, white sediment present

-

Table 6 Qualitative data for NIPPON paint

7. Data Analysis
7.1 Data processing

Calculation of percentage of precipitate formed at the end of the experiment

The percentage of precipitate formed for every experiment is calculated by using the formula below:

Mass of precipitate x 100%

Mass of paint sample

Formula 1

For this experiment, an assumption is made in order to calculate the percentage of precipitate formed as shown below:

One drop of paint sample ≈ 0.01 cm3

Assumption 1

The assumption above is made because the volume of one drop of paint sample is too small to be measured. Therefore, the smallest reading possible is taken which is 0.01 cm3.

However, the calculation is done only the experiments above shows formation of precipitate at the end of the experiments. The sediments are not included in the calculation because it still part of the paint and does not undergo any reaction. Therefore, all the calculation is shown below.

A) NIPPON PAINT CADMIUM

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cadmium

Red

Yellow precipitate in very small amount

0.02

Black

No, black sediment present

-

Yellow

Yellow precipitate in very small amount

0.01

Green

No, green sediment present

-

White

No, white sediment present

-

Percentage of cadmium in red paint = 0.02 cm3 x 100 %

0.01 cm3

= 200 %

Percentage of cadmium in yellow paint = 0.01 cm3 x 100 %

0.01 cm3

= 100 %

MERCURY

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Mercury

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

No, green sediment present

-

White

No, white sediment present

-

No calculation as there are no precipitate formed at the end of the experiment.

LEAD

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Lead

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

Yellow precipitate in very small amount

0.02

White

Yellow precipitate in very small amount

0.04

Percentage of lead in green paint = 0.02 cm3 x 100 %

0.01 cm3

= 200 %

Percentage of lead in white paint = 0.04 cm3 x 100 %

0.01 cm3

= 400 %

COBALT COMPUND

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cobalt compound

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, but solution turns to slightly blue

-

Green

No, green sediment present

-

White

No, white sediment present

-

No calculation as there are no precipitate formed at the end of the experiment.

Graph 1 Level of toxicity in percentage of NIPPON paint

B) JOHTUN PAINT

CADMIUM

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cadmium

Red

Yellow precipitate in very small amount

0.03

Black

No, black sediment present

-

Yellow

Yellow precipitate in very small amount

0.01

Green

No, green sediment present

-

White

No, white sediment present

-

Percentage of cadmium in red paint = 0.03 cm3 x 100 %

0.01 cm3

= 300 %

Percentage of cadmium in yellow paint = 0.01 cm3 x 100 %

0.01 cm3

= 100 %

MERCURY

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Mercury

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

No, green sediment present

-

White

No, white sediment present

-

No calculation as there are no precipitate formed at the end of the experiment.

LEAD

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Lead

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, yellow sediment present

-

Green

Yellow precipitate in very small amount

0.01

White

Yellow precipitate in very small amount

0.02

Percentage of lead in green paint = 0.01 cm3 x 100 %

0.01 cm3

= 100 %

Percentage of lead in white paint = 0.02 cm3 x 100 %

0.01 cm3

= 200 %

COBALT COMPUND

Confirmatory test

Color

Presence of precipitate

Mass of precipitate (±0.01 g)

Cobalt compound

Red

No, red sediment present

-

Black

No, black sediment present

-

Yellow

No, but solution turns to slightly blue

-

Green

No, green sediment present

-

White

No, white sediment present

-

No calculation as there are no precipitate formed at the end of the experiment.

7.1.1 Comparison of level of toxicity of NIPPON and JOHTUN paint

Confirmatory test

Color

Level of toxicity

NIPPON

PAINT

JOHTUN PAINT

Cadmium

Red

200%

300%

Black

-

-

Yellow

100%

100%

Green

-

-

White

-

-

Mercury

Red

-

-

Black

-

-

Yellow

-

-

Green

-

-

White

-

-

Lead

Red

-

-

Black

-

-

Yellow

-

-

Green

200%

100%

White

400%

200%

Cobalt compound

Red

-

-

Black

-

-

Yellow

400%

100%

Green

-

-

White

-

-

Table 7 Comparison of level of toxicity of NIPPON and JOHTUN paint

It is believed that all heavy metals elements present in paint are only one part of a very complex chemical formula present in the latex paint. Many chemicals are added into the paint making latex paint has composition of polymer having interpolymerized units that derive from styrene, methyl styrene, vinyl, or combinations thereof and units derived from one or more acrylates, methacrylates, acrylonitrile apart having the heavy metals elements.[5] Therefore, it is assumed that the entire heavy metals element present in the paint will dissolve in water forming ions and complex compounds. Therefore, generally, reaction that occurs is,

AX A (heavy metals ions) + X (unknown complex compound bind to the ions)

Equation 1

So, the reactions for heavy metal elements that occur are,

Ionization of cadmium

CdX(l) Cd2+(aq) + X(aq)

Equation 2

Ionization of mercury

HgX(l) Hg2+(aq) + X(aq)

Equation 3

Ionization of lead

PbX(l) Pb2+(aq) + X(aq)

Equation 4

Ionization of cobalt compounds

CoX(s) Co2+(aq) + X(aq)

Equation 5

Based on the experiment above, in experiment for testing the presence of cadmium, only red and yellow paint shows formation of yellow precipitate which is insoluble in water at the end of the experiment. The precipitate is actually cadmium sulfide which formed result of the reaction of cadmium ion in the paint with thioacetamide solution.

Yellow precipitate also formed in experiment of confirmatory test for lead in white and green paint of both brand. The precipitate formed, lead (II) chromate, Pb2Cr2O4 was results of the reaction between lead ion, Pb2+ and potassium chromate, K2Cr2O4.

­ Pb2+(aq) + Cr2O4 2- (l) Pb2Cr2O4(s)

Equation 6

In experiment for confirmatory test for the presence of cobalt ion, Co2+ and mercury, Hg2+ there are no any precipitate formed. However, both brand of yellow paint shows changes when the solution change colour to slightly blue in test for cobalt ion at the end of the experiment. The changes of colour shows that [Co(NCS)4]2- which is blue in colour.

Co2+ (aq) + KNCS( l) [Co(NCS)4]2-

Equation 7

Despite of the result shows above, in experiment of confirmatory test for mercury, Hg2+ was the only experiment that shows no changes neither in colour nor formation of precipitate. Theoretically, mercury present in black paint and at the end of the experiment, a grayish precipitate should be formed indicating the presence of Hg2+ ion[6]. This will further explain under evaluation on why the result appears no change at all.

8. CONCLUSIONS AND EVALUATION
8.1 Conclusions

Based on the experiment above, in all experiment of confirmatory test of all heavy metals ions, when mass of precipitate formed increases, then the level of toxicity in percentage of that paint is high. Therefore, hypothesis made for this experiment earlier is accepted.

In experiment A, confirmatory test for cadmium ion, the mass of precipitate formed for red and yellow paint of NIPPON paint is 0.2 g and 0.1 g respectively. So, this makes the level of toxicity in percentage of cadmium in red and yellow paint is 200% and 100%. However, the red and yellow paint of JOHTUN paint has 0.3 g and 0.1 g of precipitate formed which makes the level of toxicity of 300% and 100% respectively. So, comparing of the level of toxicity between both brand, it shows that red NIPPON paint has higher level of toxicity of cadmium than in red JOHTUN paint but has equal level of toxicity in yellow paint of both brand.

For experiment B, about confirmatory test for mercury ions, there are no precipitate formed at the end of the experiment. So, it is concluded that there are no mercury ions present in both NIPPON and JOHTUN paint making both paint free of toxicity of mercury.

Meanwhile, for experiment C, in confirmatory test for lead ions, precipitate formed in green and white paint of both NIPPON and JOHTUN paint. The mass of precipitate are 0.2 g with percentage of 200% for green paint and 0.4 g with percentage 400% for white paint of NIPPON

paint. At the same time, in green JOHTUN paint, 0.1 g of precipitate formed with 100% and 0.2 g of precipitate formed in white paint with 200%. So, both green and white of NIPPON paint has higher level of toxicity compared to JOHTUN paint.

For the last experiment, confirmatory test of cobalt ions in experiment D, 0.4 g of precipitate formed in yellow NIPPON paint while in JOHTUN paint, only 0.1 g of precipitate is formed. So, the level of toxicity of cobalt ion in NIPPON paint with 400% is much higher than in JOHTUN paint with 100%.

Overall, after analyzing and comparing of level of toxicity between NIPPON paint and JOHTUN paint, we can conclude that although the level of toxicity in both paint is very high, considering the percentage exceeds 100%, NIPPON paint has higher level of toxicity than in JOHTUN paint. So, both paint should be avoid to use widely as people will have very high risk in expose to high level of toxicity in NIPPON and JOHTUN paint.

8.2 Evaluations

Although above experiments achieved the significance of this investigation, there are few limitations should be considered and can be improvise in order to get much more accurate results in future experiments.

Firstly, in experiment A, confirmatory test for cadmium ions, it was hard to differentiate between yellow precipitate formed and yellow paint sediment when testing yellow paint sample. This is because, the yellow precipitate might be mixed together with yellow sediment at the end of the experiment. As a result, when it is weighed using with an electronic balance, the data might be the mass of mixture of the yellow precipitate together with yellow sediment instead of the mass of yellow precipitate as expected in this experiment. Therefore, in the future, right after the yellow paint is diluted, and dissolves completely in the distilled water, the yellow sediment is filtered out using filter funnel. Then only the experiment could be continue adding chemical solutions to test the presence of cadmium ions.

Besides that, in experiment B, testing on the presence of mercury ions, there are no data obtained at the end of the experiment as all sample shows no change at all; neither in change of colour nor formation of precipitate. Theoretically, mercury ions, Hg2+ should be present in black paint. However, in his experiment, because of the complex chemical composition in paint, where the black paint usually made up of vermillion which contains mercury in it, so it might impossible to assume that Hg2+ could be extracted just by dissolving the paint in distilled water. Therefore, I believed that it is not advisable in doing further experiments in testing the presence of mercury ions. This is because, the experiment might be possible to be done by using more advance technologies and other chemical solutions.

Other than that, the chemical reaction happen with precipitates formed significantly at the end of experiments, happens very slowly. The precipitates could only be obtained and measured using electronic balance after a day. Therefore, the experiments could be much faster if the mixture of paint sample and chemical solutions heated using a Bunsen burner. This is because when heat energy is apply on the mixture, it could increase the rate of collision of particles in the mixture causing more effective collision that cause reaction to happen. As a result, the rate of chemical reaction of heavy metal ions in this experiment would become much faster.

9. Further Research

The data obtained from this experiment is important in order as guideline for all people when using paint in their households. Heavy metals are widely used by paint manufacturer to continuously making paint pigments without really considering the bad effect especially to people's health if they been exposed to them for too long. Therefore it is important for all people to know the level of heavy metals present in the paint that they bought so that safety precautions can be taken seriously.

Besides that, when the paint is applied on the wall, the smell or the odor of the paint is believed to have heavy metals ion which has been oxidized into thin air which could be inhale and would probably damage body system. Therefore, a research could be done how far this theory is true by doing experiments on presence of heavy metals in thin air when paint is applied. If this theory is proven true, then people all around the world should be alert about how paint that they used may cause cancer or skin diseases if they are exposed to the paint for a long time.

Other than that, in these experiments only four heavy metals are investigated. Actually, there are many other types of paints which highly toxic because of the use of different heavy metals in the pigment. For example, barium yellow paint contains barium and chromates, King's yellow paint contains arsenic, Emerald green paints contains arsenite, Lithopone paint which contains zinc sulfide and antimony black paint contains antimony sulfide and many more. I would suggest further experiments can be carried out in order to determine the level of these toxicity in other brands of paints which are widely used nowadays.

APPENDIX

The pictures below shows the changes of colour that should be get from the experiments;

A) The presence of cadmium ions B) The presence of mercury ions

C) The presence of lead ion D) The presence of cobalt ions

Bibliography

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[1] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#CdS

[2] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#HgS

[3] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#HgS

[4] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#cobalt

[5] http://www.freepatentsonline.com/7041727.html

[6] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm

[7] http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#CdS

http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#HgS

http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#CdS

http://www.public.asu.edu/~jpbirk/qual/qualanal/confirm.htm#cobalt