*colours in ink

• Paper Chromatography


  the technique of spreading out the different mixture of ink in one colour using special filter paper and watching as the water moves up the paper to show a chromatogram.
• the coloured inks seperate bc water (the solvent) dissolves them and carries the ink particles up the paper with it.

  different kinds of ink particles travel different distances before being left behind on the paper as they don't have the same solubility and the more soluble the ink is, the further it will travel.

  permanent marker is not soluble in water but in diff solvents such as alcohol
• a large chromatography tank may be used to place spots of diff items alongside each other.

  scientists will allow the solvent to move through the samples at the same time.
• scientists use chromotography to study dyes used in foods as it is important to know what is being used when our food is processed.
• pure substance are when food dyes contain only one substance whilst other dyes contain a mixture of substances
• public health scientists use chromotography to check if colourings used in our products like hair dye or ink in pens are harmful.

  they do this by comparing the chromatogram from a solution of food, hair dye or ink with chromatograms from colourings that are permitted.