5.1.2 Filter Holder and Filter.
The filter holder is constructed of silica or borosilicate glass.
The back half of the filter holder contains a coarse frit that supports the silica-fiber filter, and an 18/9 standard socket joint leading to the condenser. The front half of the filter holder has a standard 18/9 ball joint to accept the probe exit end. A heating device such as a heated box or insulated heating tape is placed around the filter holder. The heating device and a thermocouple attached to the filter holder are connected to a temperature controller and power supply. See Fig. 711:1 for a diagram of the filter holder.