Studies were carried out on the anti-caking mechanism of sodium chloride through the use of anti-caking agents which had been proved to beeffectual even in small amount in the previous report. The results obtained were as follows:
(1) It was found out that the effect of inhibiting the growth of crystal by such agents as complexes and heavy metals was good and satisfactory. It was considered, therefore, that the anti-caking effects, were dueto the effect of inhibition of crystal growth of thesalt by these agents adsorbed on the crystals when the salt was being dried, and were also due to the effect of prevention of bridging to be made between the salt particles by the agents.
(2) The existence of a correlation was observed between the effect of inhibition of crystal growth and the effect of anti-caking in the case of ferric ammonium citrate used as an anti-caking agent.
(3) The adsorptive mechanism of potassium ferrocyanide was discussed by using the lattice distance of crystals and the ionic charge of the anti-caking agent.
(4) As the results of determination of adsorbed amounts of potassium ferrocyanide and ferric ammonium citrate, it was found that both of these agents were adsorbed in the higher concentration than that calculated from the lattice vacancies, and that, in the process of adsorption, theseagents entered into the lattice of crystals, because of those characteristics of the structure and the large ionic charges.
(5) For anti-caking of salt by using ferric ammonium citrate, the addition of 5-10 ppm was most suitable.

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The method, the degree of mixing and the yield in the case of mixing the anti-caking agent into common salt were investigated by using a push type centrifugal separator, and the following results were obtained from the above investigation.
(1) By the submerging method, the degree of mixing ought to be perfect theoretically, but it was practically effected by the characteristics of the centrifugal separator. Also, the submerging solution was spoiled and diluted by the adhesive mother liquor of salt. Therefore, it was necessary to renew the solution, while the loss of the anti-caking agent was larger.
(2) In case of mixing the agent to the salt cake in the basket of the centrifugal separator, it is unnecessary to establish a new apparatus, and moreover, the continuous process is easily kept and there is no problem of additional labor. Therefore, we think that this method is excellent in its introduction, application and practicality in the salt manufacturing process. The degree of mixing in the range of the experiment was less than 15% in the relative deviation and anti-caking effect was sufficient, and this yield was very good to the same quantity of the addition solution with the adhesive mother liquor.

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We investigated the mixing effect of a V type and a ribbon type mixer to mix the anti-caking agent, ferric ammonium citrate, into common salt. The following results were obtained from our research.
1) In case of mixing a small quantity of additional solution to common salt, we did not find such repeated phenomena of mixing and separating as those which were reported in the previous report, to occur on mixing the two kinds of dry powders.
2) We set the, operating conditions as follows: the volume percentage of charged powder was 25%, the rotation speed was 40 rpm in case of utilizing the V type mixer; the volume percentage of charged powder was 100%, the rotation speed was 40 rpm in case of utilizing the ribbon type mixer. Then, we found out that the degree of mixing was less than 10% by batch operation in the relative deviation.
3) The critical volume percentage of charged powder was the inner volume of the ribbon mixer in the batch operation, and the mixing speed decreased rapidly when the volume percentage became larger than the limit.
4) We did not find the difference between the batch operation and the continuous operation in the degree of mixing and the mixing speed, but the continuous operation was more advantageous than the batch operation, from the points of time and labor required.

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Experiments were conducted on the adding of Ferric Ammonium Citrate (FAC) solution, as an anti-caking agent, to High Grade salt. In those experiments, water solution of FAC of normal temperature was added to the salt in the head of the second basket of a continuous push type centrifugal separator by using a rectangular nozzle.
When the quantity of the salt was limited to 2.33-3.63 t/h and the adding rate of the FAC solution was fixed 14 1/h, the following results were obtained:
(1) The yield of FAC was 80%.
(2) The variation of FAC contents in samples from a produced lot was 19.5% as coefficient of variation. The quantity of a sample of the salt was 50grams.
(3) When the FAC content in the product was designed to reach 10 ppm, the content range of 2δ in the product was 6.1-13.9 ppm. In this case, the concentration of the FAC solution in the product was about 570 ppm.
(4) The increase of moisture of the product, to which FAC was added, was about 0.3% as compared with the product without FAC.

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