1. It is necessary to measure the electrical conductivity of a process solution which is prone to deposit on surfaces. Discuss the application and maintenance aspects, with technical explanations and diagrams as necessary, to show how your proposed solution operates.

2. (a) The calibration techniques for cells for measuring conductivity, pH and other ion-selection electrodes are quite different.

Explain these differences.

(b) What is the effect of immersion depth on a glass electrode?

3. What aspects of the design of a pH electrode installation would lead to reduced manual maintenance and improved reliability? Give detailed descriptions of techniques as necessary.

4. (a) An infrared gas analyser has a span of 0 - 1% of the component being measured. It operates at atmospheric pressure and was calibrated when the barometric pressure was 0.995 bar.

The barometric pressure changes to 1.015 bar. What will the

instrument read when the actual percentage of the component is

(i)  0.5%

(ii) 0.8%?

(b) A sample of gas, which is to have one component measured by IR absorption, contains another component whose absorption spectrum seriously overlaps that of the wanted component.

(i)    Why might this matter?

(ii) When it does, there are ways of clearing the system to make the measurement possible. Explain these techniques, mentioning any disadvantages.

(c) In an IR gas analyser, a 10 cm tube lets through about 70% (a reduction of 30%) of the radiation absorbed at full scale by the component being measured. Why would a longer tube be better and how much longer would be ideal?

5. (a) What methods are used in infrared, ultravoilet, and visible light systems to reduce the effects of deposition on windows and sample tube walls.

(b) Explain why is it increasingly possible to use mass spectrometry for on-line process applications.