People who play carroms know the importance of sprinkling the white, smooth powder on the carom board before the start of the play, which reduces friction and allows the free movement of the striker.
Have you ever thought about "which powder to use for carrom board? What is its chemical composition?"
The most commonly used carom powder is Boric acid (also known as hydrogen borate, Acidum boricum, boracic acid or orthoboric acid), especially in Asian countries. Boric acid has a fine crystalline structure consists of layers of B(OH) 3 molecules held together by hydrogen bonds. The distance between the two adjacent layers is 318 pm. The parallel layered arrangement makes it a good surface polish.
There is no standard carom powder and it varies from country to country. However, the most celebrated carom powder is boric acid.
Boric acid crystals were first man-made in 1702 by Wilhelm Homberg who mixed borax and mineral acids with water. The evaporating water left crystals of boric acid and was often called “Homberg’s salt.” Boric acid (H 3 BO 3 ), with the molecular weight of 61.83 containing 17.48% boron, is a colorless solid crystalline powder. It is comparatively less soluble in water only 4.73g/100mL at 20 degree Celsius. In aqueous solutions, it acts as a weak acid (pKa =9.15), which exists as undissociated boric acid below pH 7, and above pH 10 the metaborate anion dominates the solution.
Na 2 B 4 O 7 ·10H 2 O + 2 HCl → 4 B(OH) 3 [or H 3 BO 3 ] + 2 NaCl + 5 H 2 When heated above 170 °C, it dehydrates, forming metaboric acid (HBO):
H 3 BO 3 → HBO 2 + H 2 O Boric acid is used in the pharmaceutical industry as a mild antiseptic in eyewash, contact lens solutions, and vaginal remedies, in cosmetic industries as a preservative as well as antibacterial and antifungal agent in baby powder, anti-aging preparations, and similar external applications. Boron is a micronutrient and has a potential therapeutic value in promoting bone and joint health as well as having a limiting effect on arthritis symptoms and thus it is used as a nutritional supplement. In industry boric acid is used as a flame retardant since it inhibits the release of combustible gases from burning cellulosic materials, such as cotton, wood, and paper-based products. Boric acid also releases chemically bonded water to further reduce combustion. A carbon char is formed that further inhibits combustion. Boric acid is a major ingredient in the manufacture of glass and fiberglass and finds application in halogen light bulbs, ovenware, microwavable glassware, laboratory glassware, and many heat resistant everyday glass items. Boron compounds inhibit the growth of fungus and have been demonstrated to be a reliable wood preservative moreover since boric acid can be bonded with hydroxyl groups present in wood it is used to convert softwood to hardwood. Boric acid is used in swimming pools and spas as a safer and “softer feeling” substitute for chlorine. Boric acid, borax, and other salts are commonly used to soften pool water and prevent contamination. Boric acid is a natural and increasingly popular insect control product however it will not kill bugs on contact. Rather, it acts as a desiccant that dehydrates many insects by causing tiny cracks or fissures in their exoskeletons eventually dries them out, thus the effectiveness of boric acid dusts against insects reduced when dust gets wet. The “saltiness” of boric acid also interferes with their very simple electrolytic metabolism. It also acts as a stomach poison and may also have some toxic effects on the nervous system of insects. Boric acid and sodium tetraborate (all hydration states) can be used as herbicides, causing the desiccation of plants Boric acid is poisonous if taken internally or inhaled in large quantities. Commonly reported symptoms boric acid ingestion includes nausea, vomiting (often with blue-green coloration), abdominal pain, and diarrhea (which may contain blood or have a blue-green color). Other less commonly reported symptoms include headaches, lethargy, weakness, restlessness, tremors, unconsciousness, respiratory depression, kidney failure, shock, and death
Large oral exposures have resulted in an intense red skin rash within 24 hours of exposure, followed by skin loss in the affected area 1-2 days after the skin coloration first appears. These skin rashes typically affect the face, palms, soles, buttocks, and scrotum.
People processing borax at work have reported temporary respiratory irritation including dry mouth, nose, and throat, coughing, sore throat, shortness of breath, and nose bleeds after exposure to airborne particles of sodium tetraborate decahydrate. Long-term exposure to boric acid may cause kidney damage and eventually kidney failure. We should very careful during playing caroms such that the quantity of powder inhaled to be minimized