It is important to apply the reagent solution on to the layer in the finest possible dispersion, i.e., in the form of an aerosol. Home-made sprayers are frequently inadequate for this purpose, since the droplets they produce are too large. Sprayers, such as are now available commercially, for use with ninhydrin (Reagent No. 108), aniline phthalate (Reagent No. 8), bromocresol green (Reagent No. 22), etc., are ideal for this purpose1. Another appliance, which appears to be very suitable, is the “Laboratory Spray-Gun”1. This sprayer has a propellent-gas container, and the spraying reagent in the glass flask may be changed as required