The photometric method using Phenazo was applied to the determination of a small amount of magnesium in common salt. The colored magnesium-Phenazo lake had the maximum absorption of 580 mμ in sodium hydroxide solution. The proposed method was as follows:
Weigh 10g. of common salt, dissolve with water and dilute to 500 ml. exactly with water. Pipet a 5-25 ml.(Mg²⁺ 0.02-0.13 mg.) aliquot into a 100ml. volumetric flask, add 5 ml. of polyvinyl alcohol (1%), 5 ml. of potassium cyanide (1%), 5 ml. of hydroxylamine-hydrochloride (1%), 5 ml. of Phenazo (0.005%) and 5 ml. of sodium hydroxide solution (20%), and dilute to the mark with water.
The color was stable for 60 min., and sodium and calcium did not interfere. The calibration curve followed Beer's law in the range of 0.01-0.15mg. magnesium per 100 ml. of water.
The time required for the determination of magnesium was about 40 min, and good results were obtained.

View full abstract

The photometric method was investigated to determine iron (III) in common salt on the basis of the extraction with N-benzoyl-N-phenylamine (BPA) as a reagent in chloroform.
Iron (III)-BPA complex was easily extracted at pH over 1.8 and the extracted complex indicated its maximum absorption at about 435mμ, and its coloration was stable at least for 2 hours.
The light absorbancy was measured with a 420 mμ filter, and its coloration was almost constant in the pH range, 1.8 to 3.2.
The caliblation curve followed the Beer's law in the range from 0.01 to 0.1 mg. per 10 ml. in chloroform. The presence of a large amount of sodium did not interfere with this extracting procedure.
The established procedure was as follows: A 2.5-0.5g. portion, containing 0.01-0.08mg. Fe (III), of sample salt is weighed and dissolved in water, and 0.5 ml. of hydrogenperoxide solution (3 %) is added. After boiling, the solution is transferred into 100 ml. of separating funnel. After cooling, 3 ml. of ammonium acetate buffer solution (10%) of pH 2.2 is added and the obtained solution is diluted to 25ml. with water. Then, the solution is extracted with 10 ml. aliquot of chloro-form solution of BPA (0.2%).
This extracting method is suitable for the determination of a small amount of iron in common salt, and the time required is about 30 minutes.

View full abstract

It is possible to determine arsenic in common salt by Gutzeit method, but this method has some defects from the points of operation and reproducibility. Therefore, few reports have been found on the determination of arsenic contained in common salt. The present study was conducted on a spectrophotometric determination with silver diethyldithiocarbamate.
The recommended method was follows: Arsenic in sample solution is distilled by a method which is almost the same as the Gutzeit, and generated gas is absorbed in silver diethyldithiocarbamatepyridine solution (0.2%), and the arsenic is determined by measuring the absorbance of this solution at 535mμ. A micro amount of arsenic is determined after collection by coprecipitation with ferric hydroxide at pH 3-4.
This method was not influenced by diverse ions found in most common salt, and the repeatability was shown below ±0.1μg. Moreover, the operation was more simple and quickly done than other methods. Thid method was also applied to the determination of arsenic in sea water and bitttern, and good results were obtained.
The results showed that arsenic was contained by 0-31μg/kg in some kinds of common salt. The transference of arsenic caused due to the concentration of sea water at the boiling point was presumed that greater part was evaporated, smaller part was transferred to scale and sail, and arsenic was hardly transferred to bittern.

View full abstract

The present report describes scale formation in the concentration process of sea water with ion exchange membranes.
Magnesium hydroxide and calcium carbonate (Aragonite) were found on the cation exchange membranes in sea water compartments, and calcium sulfate dihydrate added to them was found on the anion exchange membranes in the concentration compartments.
Types of the scales were divided into five classes according to their shapes and compositions.
Some experiments were conduncted to elucidate the causes of scale formation. On the basis of the data thus obtained, it was confirmed that (1) the components of the scales were entirelly or locally concentrated over their solubilities and (2) the change of the pH caused by the development of concentration polarization were the main causes for the scale formation.

View full abstract

The permselectivities of sodium and hyrogen ions across the cation exchange membrane were studied by means of the electrodialytic concentration method.
As the result of the study, it was found that the permeability of sodium ions was much less than that of hydrogen ions and the ratio of the permeability of sodium ions to hyrdogen ions about 0.15-0.20.
The coefficient of permselectivity, T^Na_H, was considered almost independent of the concentration of sodium ions in the solution, and it showed a tendency to decrease with an increase in the concentration of hydrogen ions in the solution.

View full abstract