The residue on the filter paper gives (3) the substances insoluble in water.
It is then allowed to stand twenty-four hours, filtered, washed with dilute ammonia, dried, ignited to constant weight and weighed, the filter paper being incinerated separately after moistening with nitric acid.
If the precipitate may be ignited, it is transferred to a clean, weighed and recently ignited crucible, and the filter paper is burned separately on the lid, the ash transferred to the crucible, and the whole ignited.
A filter paper which has been previously heated to the temperature at which the substance is to be dried until its weight is constant.
It is washed by ejecting a jet of water, ammonia or other prescribed liquid on to the side of the filter paper until the paper is nearly full.
They are odourless and tasteless, and some yield clear aqueous solutions - the real gums - while others swell up and will not percolate filter paper - the vegetable mucilages.