微量で卓効を示した固結防止剤による塩化ナトリウムの固結防止機構を調査した結果, 大要次のような結果を得た.
(1) 錯塩ならびに重金属塩類のごとき固結防止剤を用いた場合の食塩結晶の成長抑制状態を観察した結果, 成長抑制効果がいちじるしく, したがつてその固結防止効果は塩の乾燥成長時に食塩結晶に吸着してその成長を抑制し, 架橋を防止するためである.
(2) クエン酸鉄アンモニウムについて結晶の成長抑制と固結防止効果との間に相関が認められた.
(3) 界面活性剤については成長抑制効果は認められず, したがつてその固結防止効果は表面張力の低下に基づく粒子の接着防止, さらに油性被膜による防湿, 防乾によるものと考えられる.
(4) フエロシヤン化カリウムの吸着機構について格子間隔および荷電を用いて結晶学的に考察を行つた.
(5) フエロシヤン化カリウム, クエン酸鉄アンモニウムについて吸着量を測定した結果, いずれも吸着量が多く, 食塩結晶の格子の欠陥数以上吸着されており, 吸着に際してその構造の特殊性ならびにその大きな荷電によつて結晶の格子点を占めて入ると考えられる.
(6) 固結防止剤としてのクエン酸鉄アンモニウムの食塩への最適添加量は5～10ppmである.

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押出式遠心分離機を利用して食塩に10ppm程度の極少量の固結防止剤クエン酸アンモニウムを添加混合する方法について特に添加方法, 混合度, 歩留の点について検討し次のごとき結果を得た.
(1) 一たん遠心脱水した食塩をクエン酸鉄アンモニウム溶液に浸漬して再び脱水する方法は混合は完全であるが分離機の脱水性能に添加量が影響され, また浸漬液の汚染, 液濃度の低下があり, したがつて液の更新などを必要とし損失が大きい.
(2) 遠心分離機内の食塩ケーキに添加するものは, ほとんど新設設備を要せず, 工程の連続化も容易であり, このための人件費の増加も考えられず, 製塩工程への導入, 応用性, 実用性の点ですぐれているように思われた. また実験の範囲では混合度は相対偏差で15%以内にあり固結防止効果の点でも十分であると共に歩留も食塩ケーキ付着母液と同等量の溶液添加までは添加液と母液との置換がよく98%を示したがそれ以上では損失が急激に増加する. 次に分離機スクリーン前端から添加位置までの距離による影響は実験の15～60mmの範囲では歩留, 混合度共大した変化はなかつた.

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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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