Terms & Definitions Lab 3 Flashcards
BOILING CHIPS (Stones). When should boiling chips never be used? What is the consequence of breaking these rules?
Granules of porous alundum which release bubbles of entrapped air to a solution as it is being heated. These bubbles provide a path by which the vapour of the boiling liquid can be smoothly led to the surface and released. NOTE: boiling chips can never be used twice and they shold never be added to a hot solution (ie. near its b.p.) since violent frothing will result.
BUMPING
The sudden voilent surge of vapour breaking from the surface of a liquid. If liquid is free of trapped air pockets, bubbles do not form readily and the temperature of the liquid may rise above its boiling point. The liquid becomes superheated and when a bubble does form, its internal pressure will rapidly exceed the external pressure and bumping occurs. This can be prevented using boiling chips or by stirring.
WEST CONDENSER. What is the direction of water flow?
An apparatus in which gases are cooled until they become liquid. The direction of the water flow in a condenser is always AGAINST gravity.
ICE BATH
A micture of ice and water, with a higher percentage of the latter. This is much more efficient at cooling than ice by itself.
REFLUX. What is a good reflux rate?
The process whereby a heated liquid evaporates, enters a condenser where it is allowed to cool back to the liquid state and then flow back to the original boiling solution. A “good” reflux rate is usually estimated as one drop of liquid eor second off the end of the condenser.
SATURATED SOLUTION
In a solution, it indicates that, under ordinary temperature and pressure conditions, the maximum amount of solute has been dissolved
SCRATCHING
Using the roughened end of a glass rod to pull a little of the recrystallization solvent above the surface of the liquid while “scratching” the rod against the side of the container to give the rough area for the first crystal to form.
SEEDING
Placing a “seed” or pure crystal of a substance in a saturated solution of this compount, to start the growth of the crystal lattice.
