Our preceding papers dealt with the experiments on the measurements of the concentration of the electrolytic solutions, such as NaCl, Na₂SO₄, (NH₄)₂SO₄, HCl and KOH by the use of the "High-Frequency Concentration Meter, " from the results of which experiments was concluded that the response-curves were influenced by the frequency, the shape and size of the cell condenser, the conductivity of the solution and so on.
In this paper are reported the relations between the the response-curves and such variables as described above.
(1) The frequenceies of the working oscillator of several types (containing the cell and solution) were calculated by the analytical method as the functions of the conductance, the capacitance of the cell, solution and coils and condensers of the apparatus; the results obtained being shown in Table 1.
(2) The relations between the output current or frepuency of the response-curve and the ω, c1, c2 and L were calculated and the results are shown in Table 2 and Figs. 3 and 4.
(3) The relations between the response-curve and the cell constant, frequency, temperature, etc. were calculated for the electrolytic solution, and the results obtained are shown in Figs. 5, 6 and 7.

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An autovapor or a vapor-recompression evaporation equipment has much improved by the adoption of LTV type evaporator and axial vapor compressor. Critical nature of this combination necessitates proper automatic controls. The author of this report is a member of the pilot-plant research group of the Government Chemical Industrial Research Institute, Tokyo, in which the researches on utilization of sea water have been carried on for the last few years. This pilot plant project involves the above mentioned system of evaporation process.
The paper describes first an outline of the evaporation plant in the project, then an analysis of process variables and last of all a consideration of process characteristics.
The dynamics of the whole evaporator system as a pressure-controlled process, in which heat flow rate is the manipulated variable, have a nature of single capacity process without self regulation. Lags around the final control element has a considerably bad effect on the control system. Manipulation of rate of blow-off and force-in steam flow to and from the calandria is the best way.
Interference may occur between pressure and level control systems due to coupling in the process unless proper preventive measure is taken. Cascading control of level to flow rate which is the manipulated variable of the former is an effective measure. The paper clarifies the reason why it is effective.
Finally the paper takes up briefly the other control systems and instrumentation in the plant, ending with the acknowledgment to many persons who have been of help in carrying out the project.

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Some experiences on the practical procedure of a boiler ACC are reported.
The boiler used consist of a chain grate stoker, a sectional-type water tube, and a single drum, and was heated with coke oven gas and coal, and furnished with Askania regulators with total fuel analog system.
We analyzed the control system and actually measured the time constants and examined the setting principle of the master controller and the stability of the control system.
From the practical point of view, the theoretical result showed a good agreement with the practical one, which helped us to improve the stability of the system.

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[in Japanese]

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