“Home dry-cleaning” experiment

An en­ter­tain­ing and sim­ple ex­per­i­ment that you can do with the kids, us­ing “reagents” found in the home.

Reagents and equip­ment:

• ta­ble vine­gar (70%);
• potas­si­um per­man­ganate;
• hy­dro­gen per­ox­ide (3%);
• cot­ton buds;
• cot­ton fab­ric;
• ball­point pen.

Step-by-step in­struc­tions

Dis­solve potas­si­um per­man­ganate in ta­ble vine­gar. Write some words or draw a pic­ture on cot­ton fab­ric. Then ap­ply cot­ton buds soaked in the per­man­ganate so­lu­tion to the ink. Wash away the stain with hy­dro­gen per­ox­ide.

Pro­cess­es de­scrip­tion

Potas­si­um per­man­ganate is a strong ox­i­diz­er. It can break down or­gan­ic com­pounds with a dou­ble or triple bond, for ex­am­ple the dyes in inks. The struc­ture of the inks change, and they be­come col­or­less. Ad­di­tion­al­ly, if the man­ganese so­lu­tion is left open for a while, it turns brown be­cause of the ox­i­da­tion of var­i­ous mix­tures con­tained in the air. Man­ganese (IV) ox­ide turns the so­lu­tion brown, and can­not even be washed away by wa­ter. This com­pound, to­geth­er with the un­re­act­ed potas­si­um per­man­ganate, forms an even worse stain on the T-shirt. The stain can be re­moved by a 3% so­lu­tion of hy­dro­gen per­ox­ide. In the re­ac­tion with the “stain”, hy­dro­gen per­ox­ide shows its re­duc­ing prop­er­ties. It re­duces the un­re­act­ed pink potas­si­um per­man­ganate and the brown man­ganese (IV) ox­ide to col­or­less man­ganese (II) ac­etate. And the acetic acid helps this re­ac­tion to take place, cre­at­ing a fa­vor­able acidic medi­um.

Safe­ty pre­cau­tions

If 70% acetic acid comes into con­tact with the eyes or skin, rinse them with co­pi­ous amounts of cold wa­ter, and then with a so­lu­tion of bak­ing soda.