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New method for expression of hydrogen-ion concentration
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CURRENT TOPICS.
[J. F. I.
The Fuchsin Sulphurous Acid Test.mHENRY LEFFMANN and ~IAX TRUMPER (Bull. Wagner Free Inst. Science, 1927, i i , 68-70) have made a study, in the Research Laboratory of that Institute, of the use of fuchsin sulphurous acid in the detection of methanol (methyl alcohol) in the presence of ethanol (ethyl alcohol) after selective oxidation of the former to formaldehyde. The fuchsin sulphurous acid reagent was prepared in three ways, according to: ( I ) The ninth decennial revision of the U. S. Pharmacopoeia (I9IO), (2) the tenth decennial or current revision of that treatise (I92O), and (3) the method of Fineke (Zeitschrift fiir Untersuchun 9 der Nahrungs- und Genussmittel, 1914, 27, 246). All three solutions contain fuchsin in the same concentration (o.I per cent.) ; but they differ with respect to the amount and the source of sulphurous acid, hydrochloric acid plus either sodium bisulphite or sodium sulphite. The solution prepared according to the ninth decennial revision of the U. S. Pharmacopoeia was more satisfactory than that made according to the tenth decennial revision. The solution of Fincke gave either no color or only a transient color with acetaldehyde, and a permanent color with formaldehyde. When Fincke's solution was applied in the test for methanol, ethanol never interfered with the reaction, while glycerol gave a very blue color in the absence of both methanol and ethanol. This color would be mistaken for a positive test for methanol. Therefore, while Fincke's solution has some advantages, it, like the other solutions, cannot be used in testing alcoholic liquors, other than plain spirits, for the presence of methanol, unless a preliminary distillation is made. J.S.H. N e w Method for Expression of Hydrogen-ion Concentration.--The hydrogen-ion concentration of a given solution is usually expressed as the logarithm of the reciprocal of its normality in that solution, and is designated by the symbol pH. EDGAR T. WHERRY (Bull. l/Vagner Free Inst. Science, 1927, II, 59-64) has devised a simpler, arithmetical scale for the expression of hydrogen-ion concentration. The p H values 3.0, 4.0, 5.0, and 6.0 are designated active acidities of IO,OOO, moo, IOO, and IO, respectively. A neutral solution with a p H of 7.0 has both an active acidity and an active alkalinity of o.o. The p H values 8.0, 9.0, IO.O, and II.O are designated active alkalinities of IO, ioo, IOOO, and IO,OOO, respectively. Descriptive terms are also used to further simplify the designation of reaction. When the active acidity is expressible in thousands, it is termed superacid, in hundreds mediacid, in tens subacid, and in units minimacid. Corresponding terms are used for active alkalinity. The regions of minimacidity and minimalkalinity are termed the zone of circumneutrality. Each descriptive term may be further qualified; thus, a superacid solution may have a high superacidity or a low superacidity, depending upon whether its pH is less than or greater than 0. 5. J . S . I-I.
CURRENT TOPICS.
[J. F. I.
The Fuchsin Sulphurous Acid Test.mHENRY LEFFMANN and ~IAX TRUMPER (Bull. Wagner Free Inst. Science, 1927, i i , 68-70) have made a study, in the Research Laboratory of that Institute, of the use of fuchsin sulphurous acid in the detection of methanol (methyl alcohol) in the presence of ethanol (ethyl alcohol) after selective oxidation of the former to formaldehyde. The fuchsin sulphurous acid reagent was prepared in three ways, according to: ( I ) The ninth decennial revision of the U. S. Pharmacopoeia (I9IO), (2) the tenth decennial or current revision of that treatise (I92O), and (3) the method of Fineke (Zeitschrift fiir Untersuchun 9 der Nahrungs- und Genussmittel, 1914, 27, 246). All three solutions contain fuchsin in the same concentration (o.I per cent.) ; but they differ with respect to the amount and the source of sulphurous acid, hydrochloric acid plus either sodium bisulphite or sodium sulphite. The solution prepared according to the ninth decennial revision of the U. S. Pharmacopoeia was more satisfactory than that made according to the tenth decennial revision. The solution of Fincke gave either no color or only a transient color with acetaldehyde, and a permanent color with formaldehyde. When Fincke's solution was applied in the test for methanol, ethanol never interfered with the reaction, while glycerol gave a very blue color in the absence of both methanol and ethanol. This color would be mistaken for a positive test for methanol. Therefore, while Fincke's solution has some advantages, it, like the other solutions, cannot be used in testing alcoholic liquors, other than plain spirits, for the presence of methanol, unless a preliminary distillation is made. J.S.H. N e w Method for Expression of Hydrogen-ion Concentration.--The hydrogen-ion concentration of a given solution is usually expressed as the logarithm of the reciprocal of its normality in that solution, and is designated by the symbol pH. EDGAR T. WHERRY (Bull. l/Vagner Free Inst. Science, 1927, II, 59-64) has devised a simpler, arithmetical scale for the expression of hydrogen-ion concentration. The p H values 3.0, 4.0, 5.0, and 6.0 are designated active acidities of IO,OOO, moo, IOO, and IO, respectively. A neutral solution with a p H of 7.0 has both an active acidity and an active alkalinity of o.o. The p H values 8.0, 9.0, IO.O, and II.O are designated active alkalinities of IO, ioo, IOOO, and IO,OOO, respectively. Descriptive terms are also used to further simplify the designation of reaction. When the active acidity is expressible in thousands, it is termed superacid, in hundreds mediacid, in tens subacid, and in units minimacid. Corresponding terms are used for active alkalinity. The regions of minimacidity and minimalkalinity are termed the zone of circumneutrality. Each descriptive term may be further qualified; thus, a superacid solution may have a high superacidity or a low superacidity, depending upon whether its pH is less than or greater than 0. 5. J . S . I-I.