Dry Residue

DRY RESIDUE, the residue obtained after evaporating to dryness and subsequently drying any solution, extract, or liquid of animal or vegetable origin. The dry residue shows the quantity of solid substances present in a certain volume of solution. When preparing various extracts from organs (organotherapeutic preparations), along with the substance of interest, many unnecessary and even solid substances are extracted; in such cases, the dry residue will be large; the purer the solution, the more the extract is freed from accompanying substances (salts, protein, etc.), the smaller the dry residue will be; here the dry residue characterizes to some extent the quality of the preparation. To determine the quantity of dry residue, a measured (10-15 cm³) or weighed amount of liquid is evaporated in a weighing beaker on a water bath and first dried on a water bath, then at 110-120° to constant weight. If the liquid being examined contains easily decomposable substances, evaporation and drying are carried out in a vacuum.