Boric acid
Boric acid (H3BO3) is the most readily available boron compound.
Contents
Properties
Chemical
Boric acid is quoted as being 'an acid by name only' and is even too weak to react with solids such as copper carbonate. It does not produce protons in water: it instead sequesters hydroxide ions from solution, forming H3O and B(OH)4-
Boric acid heated above 300°C looses water to eventually form boron trioxide, which can be used in a thermite reaction to produce elemental boron.
It forms a trimethyl borate ester with methanol, which burns a brilliant green, and similarly forms triethyl borate with ethanol, which also burns green.
Reaction with alkali hydroxides will form the borate salts.
Boric acid reacts in alcoholic solution with two molecules of curcumin to form rosocyanine, an dark green ionic solid that forms deep red solutions.
Physical
Boric acid is only moderately soluble in water. It is also slightly soluble in lower alcohols and acetone.
Availability
The easiest mode of acquisition is in department or hardware stores, where it is sold in relatively pure form as roach killer or other pesticides. It can also be very cheaply purchased online.
Preparation
Hydrochloric acid and borax will form boric acid, which due to its low solubility will precipitate out in cold water.
Projects
- Making trimethyl borate
- Making boron trioxide, an intermediate in the production of elemental boron
- Make elemental boron
Handling
Safety
Boric acid should not be consumed or inhaled in large amounts. Long term exposure should be limited.
Boric acid kills insects readily - it is often marketed as roach killer.
Storage
No special storage is required.
Disposal
Small amounts of boric acid can be poured down the drain, as is poses little toxicity to the environment. Larger quantities should be taken to disposal facilities.
