How to test for Formaldehyde? What is the use of formaldehyde in Daily life
Formaldehyde Tests
Formaldehyde gives all the normal tests of the aldehyde group. It gives pink color with schiff reagent, silver mirror with tollan reagent and red precipitate with fehling solution.
Specific testing of formaldehyde is as follows.
A drop of 0.5% aqueous resorcinol solution is found in 1 ml of dilute aqueous solution of formaldehyde. This mixture is slowly found in the surface of 5 ml of concentrated H2SO4. Carefully stir the test tube in such a way that both the surfaces are not lost. A ring of red violet is formed at the meeting of both surfaces.
Add 1 ml of 5% potassium pherocyanide solution to 3 ml of 1% phenyl hydrezine hydrochloride solution. In this solution, some droplets of formaldehyde solution are mixed with few drops of concentrated HCl. The color of the solution turns red. This test is called schryvers test.
A dilute solution of formaldehyde consists of a few drops of 1% phenyl hydrazine hydrochloride solution and a few drops of sodium nitroprusside solution. Dark blue color is obtained when this solution is alkalized with caustic soda. It changes color, first being greenish brown and finally red. This test is called rimmis test.
Formaldhyde Uses
Formaldehyde is a gas at normal temperature. About 30% of its aqueous solutions are called formalin. Formaldehyde is often used only as formalin. Its major uses are as follows.
- For preservation of biological and anatomical specimens
- as antiseptic
- In the manufacture of artificial colors
- In place of tanin in leather industry
- Plastic is made from formaldehyde such as bakelite galalith, formaldehyde urea.
- Urotropine derived from the action of formaldehyde and ammonia is used in urinary diseases.
- Sucking pills called formalin tablets are made from formaldehyde and lactose.
