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Equilibrium in liquid mixtures has been studied for a large number of ternary systems, but no detailed study of a quaternary system such as will be considered in this paper has, so far as we are aware, been reported.The choice of liquids to be used was based on the ease of purification and analysis, the particular system studied being composed of acetone, acetic acid, chloroform, and water at a temperature of 25°C. PURIFICATION OF THE FOUR COMPONENTSPure glacial acetic acid crystals were prepared by equilibrium melting, and the resultant acid was freed from water by distillation with the addition of ethylene dichloride. The ethylene dichloride was found to be stable in boiling acetic acid solution, no chlorine derivatives being formed.Analar acetone was dried over calcium chloride, filtered, and fractionated. The fraction distilling at 56.0°C. at 760 mm. was employed.Distilled water was treated with solid barium hydroxide, filtered, and redistilled.Analar chloroform was fractionated and the fraction boiling at 61.1°C. at 760 mm. was employed.All solutions were stored in clean dry Winchester bottles, fitted with soda lime tubes and hand pumps for transfer of reagents. Air in the storage bottles was previously displaced by nitrogen.METHODS OF ANALYSIS 1. Chloroform A method was developed for the estimation of chloroform, based upon the formation of potassium chloride by treatment with alcoholic potassium hydroxide, the potassium chloride formed being titrated with silver nitrate. About 5 ml. of chloride-free normal alcoholic potassium hydroxide was weighed in a small stoppered glass tube. A few drops of chloroform were 683

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General information of the conditions under which 18-8 stainless steels corrode aids in establishing conditions to minimize failure in this and similar steels. Detailed study was made of the effect of temperature, concentration, and pH of aerated sodium chloride solutions, noting the nature of corrosion and corrosion rate for 24-hour periods. Corrosion of 18-8 increases sharply with temperature, going through a maximum at approximately 90°C. for 4 and 10 per cent sodium chloride and above 90°C. for 1 per cent solution. Corrosion is by pitting. At the boiling point corrosion decreases to nearly zero in 24-hour tests owing to lack of dissolved oxygen.Increased salt concentration at 90°C. increases corrosion of 18-8 from zero in distilled water to a maximum at 4 per cent sodium chloride. Identical tests with mild steel show significant corrosion in distilled water and maximum corrosion in 2 per cent sodium chloride. At higher concentrations corrosion is less, dropping off more rapidly for mild steel. In 25 per cent solution the corrosion rates of 18-8 by pitting and mild steel by uniform solution approach each other. At 90°C. in 4 per cent sodium chloride the logarithm of corrosion weight loss is a linear function of pH in the range pH 12 to 8. Corrosion falls off rapidly below pH 5, goes through a minimum at 2.9 to 4.5, and increases sharply at 2.9. Pitting is observed above pH 2.8, and uniform solution accompanied by hydrogen evolution occurs in more acid solutions. The number of pits per square decimeter follow the minimum and Vol. 33, No. 7 maximum of corrosion plotted with pH. Maximum pit penetration occurs at pH 6 to 7.The effects of pH in the alkaline region are explained on the basis of increasing effective cathode areas surrounding the pits with decrease in pH. The corrosion minimum is accounted for by partial breakdown of passivity. The sharp upturn of corrosion at pH 2.9 is due to corrosion by hydrogen evolution.The results indicate that at 90°C. corrosion of 18-8 in aerated sodium chloride solutions is less if the solutions are made acid to pH 3 or 4. Least corrosion occurs in the alkaline region of pH 12.

In the first part of this article, in our last issue, DR. BRANCKER discussed the fundamental elements of emulsification, the orientation and wetting theories and their connections with lubrication. In this part he discusses metal cleaning, solid emulsions and atomisation. The theories discussed are of primary importance in connection with spraying metal surfaces for corrosion inhibition or for lubrication. The theories of atomisation are also important in connection with lubrication by aerosols.