Question

Cobalt chloride method was first used by

• A. F. Darwin (1912)
• B. Stahl (1894)
• C. Curtis (1926)
• D. Leibeg (1840)

Answer 1

The correct option is B Stahl (1894)

Stahl (1894) described the hygrometric method or cobalt chloride paper test. Dry cobalt chloride is blue, while the moist one is pink. A filter paper slip can be dipped in cobalt chloride and dried. It will appear blue. The slip is placed over leaf surface and protected from atmospheric humidity. Change in colour of the filter paper slip from blue to pink indicates transpiration.