Nitrate test to 2.5 micrograms and a concentration of 1 in 25,000 parts. Devarda's alloy (Copper/Aluminium/Zinc) is a reducing agent. When reacted with nitrate in sodium hydroxide solution, ammonia is liberated. The ammonia formed may be detected by its characteristic odor, and by damp red litmus paper's turning blue, signalling that it is an alkali — very few gases other than ammonia evolved from wet chemistry are alkaline. Aluminium is the reducing agent in this reaction that will occur. Diphenylamine may be used as a wet chemical test for the presence of the nitrate ion. In this test, a solution of diphenylamine
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,