Solubility Curve of Potasium Nitrate

Determining the solubility of potassium nitrate at different temperatures.

The temperature at which Potassium Nitrate begins to precipitate out of a solution was measured to find the solutions maximum concentration. Each time one more millilitre of water was added the solution was re-heated. The more water that was present the lower the temperature was that the Potassium Nitrate began to precipitate.


Table 1

Solubility in g/100ml ml of distilled water Temp in °C Precipitate formed
150 g/100ml 2.0 ml 75 °C
100 g/100ml 3.0 ml 62 °C
75 g/100ml 4.0 ml 59 °C
60 g/100ml 5.0 ml 49 °C
50 g/100ml 6.0 ml 42 °C

The solubility of Potassium Nitrate is directly effected by the temperature of the solution. As the temperature of the solution rises the solubility of Potassium Nitrate increases


 Sources of error in the experiment include; possible inaccuracy of equipment, miss measurement of materials, the difference between what one person would determine as a crystal compared to another, the time between when the temperature was recorded and when the first crystal was spotted. Ways to improve and/or eliminate these flaws would be to have the same person each time watch for crystals to form and to have the thermometer always in the test tube.

Ways to alter the experiment for more similar results would be to instead of changing the amount of water that is in the solution, the amount of Potassium Nitrate could be altered instead


In this lab the purpose was to; determine the solubility of potassium nitrate at different temperatures. It becomes clear that solubility of potassium nitrate  is directly affected by temperature, for example at 79 °C the solubility is 150g/100ml where at 62°C the solubility is 100g/ml. Therefore at higher temperatures potassium nitrate is more soluble. (which should come as no surprise as this is true for most solids that dissolve in water. 

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One Response to “Solubility Curve of Potasium Nitrate”
  1. carlos Says...

    On June 29, 2011 at 9:20 am

    very handy ma8, well done

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