Automatic fraction collectors and a conductivity recorder.

In recent years a variety of designs of automatic fraction collectors have appeared (Brimley & Snow, 1949; Cuckow, Harris & Speed, 1949; Edman, 1948; Phillips, 1949; Stein & Moore, 1948). The collectors described here possess the advantages that they are simple and cheap to construct and have given reliable service over long periods. The three machines all operate on the same principle, involving a siphon set on a balance arm which, in filling and emptying, operates a mechanical escapement. The siphon and its delivery arm are caused to rotate by means either of a spring, a twisted cord or a small weight. The first two single-row machines differ only in arrangement of siphon, the second being the more robust. The third machine has several rows of tubes and is consequently more compact. The movement from one row to the next is accomplished with the aid of a second escapement.