Home Chemistry 4 – Indicators
For some reason, the universal indicator paper I have isn't working properly, it could be as it is quite old.
Nevertheless it does seem that if emersed in Water, the chemicals within leech out. I tried this with a few pieces and it has produced a nice blue colour.
So I am assuming that the liquid produced can act as an acid / alkali indicator.
So to investigate further. I am going conduct an investigation.
Equipment
- Test tube rack
- 2 Test tubes
- Beaker with indicator solution
- Dropper
- Spatula
Chemicals
Both in powder form.
- Bicarbonate of Soda
- Citric Acid
Predictions
- Bicarbonate of Soda – Should change colour towards Purple (Alkali)
- Citric Acid – Should change colour towards red (Acid)
Method
- Add Bicarbonate of soda to 1 test tube
- Add citric Acid to the other
- Make a note which is which
- Using a dropper add some of the indicator to each of the test tubes
- Note colour
Results
Colour changes noted as follows:-
- Bicarbonate of Soda – Stays blue
- Citric Acid – Does turn a very pale pink colour
Conclusions
I don't think I had an indicator in the first place, as this was blue,any change in colour would not be very noticeable with the addition of the alkaline bicarbonate of soda.
I would have expected the citric acid to be a clearer colour to indicate acid.
I think my indicator paper is simply out of date due to age.
Recommendations
- Repeat part of this experiment using fresh indicator paper, only just use the paper to test the above two chemicals mixed with water. As the paper needs a liquid to work anyway.
- Throw old papers away and buy new.
Update
As confirmed on Science forums the indicator paper has degraded and needs to be replaced. So my Hypothesis as to the issue was on the right track.
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