pH of different soap samples

These Soaps are salts made from mixing of animal or vegetable oils (acid) with Sodium hydroxide NaOH or Potassium Hydroxide (KOH)(base). Simply says, pH value of a bathing soap should be around 7.5 - 9. It should be partially alkaline. pH 7 is neutral - Plain water

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Aim- To find the pH of different soap samples:
i. Santoor
ii. Fiama di wills
iii. Breeze
iv. Keto soap
v. Dove
vi. Lux
Apparatus Required- A beaker, a dropper, pH paper distilled water,
given samples, white glazed tile, etc.
Principle- The hydronium (or hydrogen) ion concentration of a
solution can be conveniently expressed in terms of pH. The pH of a
solution is defined as the negative logarithm (base10) of hydronium
(or hydrogen) ion concentration.

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The pH generally extends from 0 to 14.

The approximate pH of a given solution can easily be obtained by
using wide range pH paper or universal indicator. The colour
developed is matched with the colour in the colour chart and
corresponding pH value noted.

Colour chart with corresponding pH value

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Ques. What is a pH paper?
A pH paper is a strip of paper which after dipping in a solution of
various indicator, has been dried up. When it is dipped in a given
solution, it changes its colour. The shade of formed is compared to the
chart provided for this purpose from which approximate pH can be
found out. The pH papers are available in strips of 20-25 in the form
of a small booklet. Its cover contains the chart of color for
comparison.



pH paper booklet

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Procedure-
i. Take soap and peel off small shaving of soaps and dissolved it in
into water.
ii. Tear a small portion (1-2 cm) of pH paper with clean and dry hands
and place it on a white glazed tile.
iii. Using a dropper transfer 1 to 2 drops of the first sample of the soap
on the universal indicator paper (pH paper).
iv. Observe the colour developed on the pH paper and compare it with
the colour in the colour chart on the cover of pH paper booklet.
v. Note the pH given against the colour which tallies with the colour
developed on the pH paper.
vi. Repeat the procedure given above, for the other samples and note
your observations.

Correct use of pH paper with dropper

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Observation -






S.NO. SAMPLES TAKEN pH OF THE SAMPLE
1 Santoor 9
2 Fiama di wills 8
3 Breeze 9
4 Keto soap 9
5 Dove 7
6 Lux 9

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Result- Acidic samples are: - None
Neutral sample is: - Dove
Basic sample are: - Santoor, Breeze, Keto soap, Lux

Precautions-
i. Wash the test tube thoroughly with distilled water, before
use.
ii. Use clean and dry hands to tear a pH paper.
iii. Wash the dropper thoroughly after testing each sample.
iv. Clean and dry the glazed tile before use.
v. All solutions should be freshly prepared.