a method of microchemical, qualitative, or semiquantitative analysis in which both the solution to be analyzed and the reagents are used in amounts of several drops.
The detection of certain ions makes use of characteristic color reactions, which are carried out on filter paper, watch glasses, drop plates, or microcrucibles. Spot test analysis uses reagents of great sensitivity and selectivity, making it possible to detect the given ions in the presence of other components in the solution to be analyzed. Semiquantitative analysis (spot test col-orimetry) is performed by comparing the intensity of coloration of spots obtained on filter paper with the color of a standard. The spot test has the advantages of speed, simplicity of equipment, and a high degree of sensitivity (detection limit of ions, 0.1-0.01 microgram). The method is widely used to identify materials and control their purity, for ore and mineral and biochemical analyses, and for many other purposes. Spot test analysis is particularly convenient under field conditions for the quick analysis of industrial samples.