solvent, the amount of recrystallization, should in consideration of the two factors. less solvent, high yields, but probably for heat trouble, and possibly even greater losses; solvent, obviously on the recovery. the two should be taken into account. generally requires more than 20% of the solvent, some say it is in general more than 20 - 100% solvent).
secondly, in a boiling temperature, dissolution of solid, but we must be careful about how much, in fact, the temperature is so practical, crystal precipitation much purified. but for some crystals are not cleaned, you can at the boiling point of the solvent dissolved in saturated solution, because of the special circumstances of the decision can not be generalized. for example, the tests were carried out in 100 in the saturated solution, temperature and heat filter doesn't work 100, maybe 80. ??? ??? ??? 90? how many solvent think should be taken into account in the filter operational temperature.
three, in order to avoid that the solvents and flammable solvent fire or toxic solvents, poisoned in the erlenmeyer flask device reflux condenser, addition of solvent from the condensing tubes.
4, if the solution containing colored impurities by activated charcoal, should be given special attention, the use of activated carbon.
while the five heat filter (1) when a combustible solvent should be, in order to prevent the fire or prevent solvent evaporation.
(2) if on filter paper method and operation (including the funnel water wetted preheat, filters, etc.) and should be cleaned, the size of the flask, filter paper, filter paper wetting operation starts with pressure, in order to prevent a filter paper (in the hot solvent, filter paper sharply).
six of the
(1) at room temperature, or heat from the static cooling (e.g., slowly the crystals dissolved, heated, crystallized with cold water, sufficient to kühlen.notwendig, with water or ice and salt (as in this case, if the solvent in cold water or ice with salt water can the crystallization. he can't take these steps).
(2) sometimes, because the substance of tar or jelly with there so that the crystallization or sometimes not easy to separate, the supersaturation solution of crystals in this case, the wall with glass rod friction form a rough surface, the orientation of the solute molecules form a crystallisation in the smooth surface of the quickly and easily; or the seeds (the same material crystals, the crystals when the material with a glass rod, a solution is slightly dried, the crystals) the nuclei which quickly the crystals form.
(3) to be cleaned separately, sometimes with oily, while the oily substance by a long time after the static or sufficient cooling can be cured, but such solid often contain more impurities (impurities in oil substance often as a solvent in the solubility in large; secondly, a sound also reflected part of the mother liquor), whose purity is not high. many solvents, can prevent oily substance, although the product is produced but large losses.
at this time, the solution can be precipitated wax heated, then slowly abgekühlt.wenn oil cloth is made more intense mixing mixture, the oily substance uniformly condition in the system, but the best is you want to choose again, the solvent, the crystal products.