The spectra which occur from oxidizers and other inorganic substances

Potassium chlorate, potassium perchlorate etc, which contain potassium atoms create undesirable spectra continuous spectrum caused by the atoms and atomic line spectra. The former appears in almost all the visible zone and is the most intensive at about 4500A(blue). This spectrum makes the flame white, and sometimes it is used to produce a white flame. This spectrum cannot be rejected unless the potassium salts are precluded from the composition. If good colouring is desired, ammonium perchlorate must be used in place of above oxidizers. In the latter, the atomic line spectra are very weak and do not much disturb the colour. 

Strontium compounds, such as strontium nitrate, carbonate etc.,produce an intensive Sr line 4607A(blue), which cannot be avoided whenever we use these substances. The intensity of the line is smaller than that of the useful bands, SrOH and SrCl, but it rather pulls the red towards the violet. 

Generally impurities in the oxidizers or other inorganic materials disturb the flame colour. Strontium salts usually contain some barium salt as an impurity which produces the undesirable spectrum BaCl or BaOH band and disturbs the colour of the flame. Accordingly it is necessary to use strontium salts of high purity to obtain a good red flame. Strontium and barium belong to the same group of elements, and it is difficult to separate barium and strontium salts industrially, but in a laboratory strontium salts can be purified until they have a barium content of less 

Na-D lines appear in almost all cases because every inorganic substance in firework composition contains sodium compounds as an impurity. The Na-D lines disturb any flame colour except a yellow flame. It may be difficult to obtain perfectly Na-free ingredients, but we must endeavour to get materials with a minimum sodium content. 

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The spectra which occur from oxidizers and other inorganic substances... 

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