Suspending bridge method

The more common method of forming solid bridges by recrystallization of dissolved substances or deposition of suspended colloidal particles is to evaporate the liquid. 

Cotton cellulose is the filtermass used in brewing, but -wood cellulose is also available. It is sometimes used as underlay for diatomite or perlite or as a blend with diatomite. Generally the fibres are about 20 pm diameter and 50-100 pm long, which win bridge wide openings in the filter medium Cellulose is very pure, is combustible and soluble in solvents so that inert suspended solids may be recovered by either of these methods. 

The sensitivity difference between direct flame and furnace atomisation has been bridged via the general method of atom trapping proposed by Watling [1]. A silica tube is suspended in the air - acetylene flame. This increases the residence time of the atoms within the tube and therefore within the measurement system. Further devices such as water-cooled systems that trap the atom population on cool surfaces and then subsequently release them by temporarily halting the coolant flow are sometimes employed. The application of atom-trapping AAS to the determination of lead and cadmium has been discussed by Hallam and Thompson [2]. 

Some basic control experiments were carried out, however, using this system and the circuit shown in Fig. 84. After considerable effort in which various time constants in the circuit were changed over fairly wide ranges, the system was made to control the rate of boiling. However, there was a bad shunting effect which was not easy to eliminate and, since the 1000-cps bridge system seemed to be operating in a satisfactory manner, work on the noise-detection method was suspended. 

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