Litmus "Lecanora tartarea" (Norway, Sweden), "Variolaria dealbata", "Ochrolechia parella", "Parmotrema tinctorum", and "Parmelia". Currently, the main sources are "Roccella montagnei" (Mozambique) and "Dendrographa leucophoea" (California). The main use of litmus is to test whether a solution is acidic or basic. Wet litmus paper can also be used to test for water-soluble gases that affect acidity or alkalinity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turn the red litmus paper blue. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or
Test of Variables of Attention has no diagnostic terms and is used by school-based professionals. The T.O.V.A. measures a set of different variables to determine whether or not response times and attention is at the normal range for the sex and age of the test taker. Over 2000 people without attention problems were measured to determine what is a normal response time for the sex and age of the test taker as a basis for the interpretation provided. One of the major strengths of the TOVA test is the use of a microswitch to record response time. The microswitch can obtain very accurate response times,