4. Test For Acidity

Introduction

This method determines the exact value of pH found in local and foreign fruits and vegetables, using universal indicator for an estimate and then re confirming with a more accurate test using a pH metre connected to a data logger. The data logger I set to give an exact value to two decimal places. Once the universal indicator is in contact with the juice it will instantly change colour according to pH level and then compared to a universal indicator chart chart.

 

Apparatus and materials:

 

For estimate test:

·         Universal indicator

·         Pipet

·         Juice extracted from different fruits and vegetables

·         Juice extractor

·         Test tubes

·         Test tube rack

 

For a more accurate test:

·         Data logger

·         pH metre

·         small 25mL beaker

·         juice extractor

·         juice extracted from different fruits and vegetables

 

 

Estimate test:

 

1.    One first extracted juice from all three fruits and vegetables using a juice extractor.

2.    The juice obtained was then passed through a cheese cloth to ensure that no chunks where present and that it was entirely              liquefied.

3.    The three different resulting juices were each placed in three different test tubes.

4.    After, about 2cm2 of universal indicator was poured into each test tube using a clean pipette that was washed with distilled              water and stirred.

5.    The solutions quickly changed colour and the colours were compared to a universal indicator chart.

 

A more accurate test:

 

1.    To get a definite result one used a data logger connected to a pH metre.

2.    One first extracted juice from all three fruits and vegetables using a juice extractor.

3.    The juice obtained was then passed through a cheese cloth to ensure that no chunks where present and that it was entirely              liquefied.

4.    The three resulting juices were placed in a small 100mL beaker and the pH metre was placed and stirred in all of them.

5.    After each juice one stirred the pH metre in distilled water to prevent contamination and false readings.

6.    The data logger was programed to obtain a reading to one decimal place. 

7.    Once the experiment was carried out the pH metre was placed in a bottle like tap containing storing solution to prevent it from        getting damaged.