Flame photometer, c 1960s.
© Science Museum / Science & Society Picture Library
In this device, a standard sized flame is produced by gas and air mixed at a fixed presure in a chamber from which the mixture pases to a spray system. There it picks up fine drops of a solution of the sample under test so that when the flame is formed it is affected by any metals present in the solution capable of giving a flame colour; for example yellow for sodium and red for calcium. The greater the amount of metal present in the sample, the brighter the colour.