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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Vol. 9, No.
II
NOTES AND CORRESPONDENCE A SOCIETY OF CHEMICAL INDUSTRY IN FRANCE The following extract from a circular now being sent out is self-explanatory : To the Chemists &f Manufacturers of America: There has been formed in France a French Society of Chemical Industry, the Societe de Chimie Industrielle, whose objects are fully set forth in the attached letter (not given here) of Mr. Paul Kestner, President of the Society. After consultation with Mr. R e d Engel, Secretary of the Society and a member of the French Scientific Mission in the United States, the undersigned committee believes that it would be most opportune to establish an American section of the Societe de Chimie Industrielle and thus extend to our French fellow chemists and manufacturers, our moral and financial support and the right hand of good fellowship. Furthermore, members of the American section will benefit by the closer relations which will naturally develop between American and French Chemical Industry. Jerome Alexander Charles A. Doremus Charles I,. Parsons
Leo H. Baekeland Raymond F. Bacon Wilder D. Bancroft Charles Baskerville Albert Blum Henri Blum Marston T.Bogert M. Ceresole Arthur M. Comey
John V. N. Dorr W. M. Grosvenor Frank Hemingway Ellwood Hendrick Chas. H. Herty J. B. F. Herreshoff George F. Runz Parker C. McIlbiney William H. Nichols R. E. Orfila
Charles I,. Reese Allen Rogers Samuel P. Sadtler Maximilian Tocb G. W. Thompson G. E. Vdabrigue E. P. V. Verge Henri Viteaux C. B. Zabriskie
After the above introduction the circular contains the translation of a letter addressed by Mr. Paul Kestner, President of the Society, to the chemists of France, an extract of the ByLaws of the French Society, the list of officers of the Society, and a blank to be used as an application for membership in the American Section of the Society. Copies of this circular may be obtained by addressing the “Organization Committee of the American Section of the Societe de Chimie Industrielle, c/o Chemists’ Club, 50 East 41st St., Ne‘w York City.”
TWO LETTERS ON THE AVIDITY OF SOIL ACIDS Editor of the Journal of Industrial and Engineering Chemistry: In an article appearing in THIS JOURNAL, 8 (1916), 344, Truog describes a method which he has developed for the measurement of the avidity of the active soil acids. Briefly, his method is as follows: To a weighed sample of soil is added an amount of potassium acetate solution which contains an amount of the salt equivalent to the active soil acids in the sample. The active soil acids are previously found by determining the amount of standard barium hydrbxide it takes t o neutralize the soil acids in a given length of time. Potassium acetate solution and soil are shaken together for two minutes when the mixture is filtered and an aliquot of the filtrate titrated with sodium hydroxide solution, using phenolphthalein indicator. The avidity is calculated from the followihg formula, the chemical symbols standing for equivalents: NaOH KCtHaOz - NaOH This factor times the avidity of acetic acid, taken arbitrarily as 1000,gives the avidity of the soil acids. Truog points out that since the soil acids are relatively insoluble, the avidity as found does not represent the strength of the soil acids, compared t o acetic, but that the avidity figures for different soils are comparable with each other because the acids are all quite insoluble. The purpose of this note is to point out that Truog does not in any sense of the word measure the avidity of the soil acids. In none of the text books of physical chemistry is any mention made of a titrimetric method for the measuring of the strength of acids. It is not the place here to go into a discussion of these methods. I n the 4th English edition of Nernst’s “Theoretical Chemistry” on pages 557 to 563 an outline of the theory of the
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various methods is given, and, obviously, it is theoretically wrong when determining the strength of acids to titrate. Truog’s method measures nothing more nor less than the amount of acids soluble in potassium acetate. Whether or not such a knowledge is of value we do not wish to discuss here. R. S. POTTER IOWA STATECOLLEGE EXPERIMENT STATION AMES. IOWA,September 12, 1917
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Editor of the Journal of Industrial and Engineering Chemistry: . I n reply to the criticisms of R. S. Potter regarding the method proposed for the determination of the avidity of the active soil acids, I wish t o state as follows: The avidity of an acid has reference t o its relative strength, affinity or competing power for a base. Various methods have been proposed for the determination of the avidities of the common water-soluble acids. Thomsen’s thermochemical method and Ostwald’s volume method have been most widely used. Physical properties such as refractive indices, rotary powers, catalytic effects, electrical conductivities and biological effects have also been used to determine the relative strengths of acids. AS the writer has indicated in the Journal of Physical Chemistry, 20 (1916), 473, soil acids are usually Comparatively insoluble and hence the methods proposed for use with the common soluble acids cannot be used in the case of soil acids. I n the method proposed by the writer for the determination of avidity, the active soil acids are first determined quantitatively. By active soil acids is meant those acids which react with a soluble base almost instantly. Although these active soil acids are for the most part not in true solution, yet their physical condition is such (colloidal) that they react with surprising rapidity and some exhibit considerable avidity. After the amount of active soil acids has been determined, a known weight of soil is treated with a solution containing an amount of neutral potassium acetate which is chemically equivalent t o the active soil acids present. The single addition of the potassium acetate is equivalent t o adding separately, chemically equivalent amounts of acetic acid and potassium hydroxide. There results thus virtually the condition that chemically equivalent amounts of active soil acids, acetic acid and base in the form of potassium hydroxide are present in the mixture. The active soil acids are thus given an opportunity t o compete with an equivalent amount of acetic acid for a definite and equivalent amount of base, as is done in Thomsen’s thermochemical method and Ostwald’s volume method. Obviously thermal effects or volume effects cannot be used t o determine the distribution of the base between the active soil acids and acetic acid. However, since the base that combines with the active soil acids forms salts which are comparatively insoluble in water and leaves in solution an amount of free acetic acid which is chemically equivalent to the base that the active soil acids have removed from solution, it is only necessary t o filter the mixture and determine in the filtrate by titration the amount of acid present, in order to determine the amount of base which the active soil acids removed while in competition with an equivalent amount of acetic acid. By substitution in the formula comparative figures for different soils are obtained. The figures represent the collective, or better, average avidity of all the active acids in any particular soil sample. As far as the writer is aware the method described in THIS JOURNAL, 8 (1916), 344, is the only method that has ever been proposed for use in case the acids are not in solution, and it is not at all surprising that Potter finds no mention of a titrimetric method in the text books of physical chemistry. Such methods as are mentioned, are for use under conditions in which the acids and salts formed are in true solution, and obviously
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