DIALY′′SER

In practical chemistry , an instrument for separating ‘crystalloids’ from ‘colloids,’ introduced by the late Prof. Graham. In its most convenient form it consists of a hoop of gutta perch a, over which a circular piece of parchment paper is stretched. The paper is applied to the hoop while wet, and is kept stretched by a second hoop, by an elastic band, or by a few turns of string. The instrument, when complete, resembles an ordinary tambourine. It is distinguished as the ‘ HOOP DIALYSER ,’ The fluid to be ‘dialysed’ is poured into the hoop upon the surface of the parchment paper, to a small depth only, such as half an inch, and the dialyser is then floated upon water in a large gla basin. Another form of dialyser, termed the ‘ BULB DIALYSER ,’ consists of a small gla bell-jar, the mouth of which is covered by a piece of parchment paper. This is suspended or otherwise supported in a large ve el of water in such a manner that the parchment paper septum just dips below the surface. See Dialysis (below), Parchment paper .