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
Fehling's solution the starch sugar. Formic acid (HCOH) also gives a positive Fehling's test result, as it does with Tollens' test and Benedict's test also. The positive tests are consistent with it being readily oxidizable to carbon dioxide. The net reaction between an aldehyde and the copper(II) ions in Fehling's solution may be written as: or with the tartrate included: Sodium hydroxide is corrosive. Fehling's solution Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functional groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test. The test was developed