Double block technique

According to Eq. (68) we now also expect an oxygen vacancy depletion, and in fact a much more severe one according to the double positive charge. The separation of electronic and ionic conductivity by a blocking technique confirmed the predictions in detail (Fig. 33134). 

A similar technique, more common with air systems, is to automate the familiar double-block-and-bleed arrangement. The first step in this design might be to replace a simple check valve with a differential-pressure control valve that shuts when the pressure differential reverses. This affords two levels of protection, unless one assumes that the check valve is fundamentally untrustworthy and always allows somebackleakage. Check valves can, of course, be made more reliable by proper installation and by extra measures such as force loading. An elaboration on the diagram above is to add a second valve in the line that closes when the differential pressure is too low or even negative. Finally, the space between the two in-line check valves can be vented for more positive protection. 

Another valiant on the basic isotope dilution technique is that of double isotope dilution, or valiants thereof, as first proposed by Block and Anker (1948). It is used in reverse IDA where the specific activity of the original unknown radioactive material A cannot be measured for some reason. Hence a second dilution is made to determine the specific activity of the original sample. 

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