In this work, the magnesium content was determined by the solution scanometric method using titan yellow (TY) as a complexing agent in alkaline media. This method is based on scanning a solution containing the pink-coloured product of the combination of TY and the magnesium hydroxide complex. Hydroxylamine hydrochloride (HA) and starch were utilised as colour stabilizers and protective colloids, respectively. After the cells containing the sample solution were scanned, the colour of each cell was analysed with software written in Visual Basic (VB 6) in terms of the red, green and blue values. The parameters used for optimisation include the reaction time and the concentration of TY, sodium hydroxide, starch and HA. The system had a wide linear range between 0.070 and 30.000 g mL −1 concentrations of magnesium, with a detection limit of 0.058 g mL −1 and a relative standard deviation of 1.90% for the G colour value. In addition, the effects of some foreign species were investigated. The method was successfully applied for the determination of magnesium in almond gum and three water samples.