The interactions of p-dimethylaminobenzaldehyde (p-DAB) and potassium hydrogen sulphate (PHS) in equimolar ratio with various concentration of diphenylamine (solid test material) have been investigated by capillary spot-tests technique in order to investigate the effect of temperature and volume of material in test-tube. The formation of the colored boundary in the capillary is taken for the detection of organic compounds by spot-tests at different temperature and volume of solid test material.