the reaction between silver chloride and sodium hydroxide is largely complete. Actually, the apparently large value of the ratio has little meaning in terms of the final equilibrium conditions, since the concentration of the silver ion is reduced more than 5000 times as soon as the reaction has progressed t o a slight extent. One may calculate a t least roughly the extent of the metathesis of silver chloride by a solution of sodium hydroxide. At equilibrium both solubility product equations are simultaneously true: [Ag+][cl-] = 1 X lo-'o
To the Editor:
and Recently my attention was called t o the method of k + I [OH-] = 1 X 10-0 reclaiming silver from silver chloride residues as described by Mr. Otto L. Willbanks in TRIS JOURNAL, 30, By simple division one obtains the ratio between the 347 (1953). One of the members of our department had concentration of the chloride and of the hydroxyl ions. tried the method and was disappointed with the rela[CI-1 = [OH-]/100 tively small yields of silver oxide that he was able t o obtain in relationship to the amounts of sodium hy- This result indicates that for every mole of sodium hydroxide used only one hundredth of a mole of silver droxide used. There is nothing in Mr. Willbanks' article that sug- would be obtained as silver oxide. I n terms of grams e&s that the "vield of silver oxide is Door. I n fact. it the yield, one gram of silver for each 37 grams of would appear that the author's statement that silver sodium hydroxide, sounds somewhat better. However, chloride, under the given conditions, "furnishes 5000 in spite of the difference in the cost of sodium hydroxide times the silver ion concentration required for the pre- and that of silver, this yield is hardly one that would cipitation of silver oxide," was meant to suggest that delight the heart of a manufacturer of chemicals.
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Mr. Willbanks indicates that the method may be used for the reclamation of other silver salts, such as the thiocyanate. The solubility product of silver thiocyanate is approximately one hundred times less than that of the chloride. Accordingly, t o obtain one gram of silver from silver thiocyauate by this method, approximately 3700 grams of sodium hydroxide would be required.
T o the Editor: I have read with great interest the article titled "Industrial advertising as a source of information," by W. G. Kessel (THISJOURNAL, 31, 255 (1954)). From the point of view of instruction in the classroom this source of knowledge has no workable substitute. Teachers, by and large, are both book-bound and classroom-bound. They follow the book and they spend most of their days in the classroom. Textbooks, however up-tc-date or modern, generally do little with industrial applications and developments. They spend their pages developing theory, and perhaps justifiably so. Reference might be made to an industry or t o a product by way of fine print or a black-and-white photograph, but these are not worth much pedagogically. As for the teachers, they are constrained to the classroom. The so-called field trip with a class to a plant or factory is pitifully infrequent, but pretty nearly inescapably so. Since the student cannot easily be brought to the plant or to the product it appears both necessary and worth while t o bring these to him. Industrial advertising
JOURNAL OF CHEMICAL EDUCATION
does it in good measure. By this device new products, new processes, new words are discovered. There is no better source of the latest. And it is most certainly not in the textbooks. A few years ago a colleague and I pursued a program which paid high in stimulation and enthusiasm personally, and which added immeasurably to our usefulness in the classroom. We reserved one afternoon a week to visit plants and industries-alone, not with classes. (This last is too difficult to "machine.") Our program was scheduled in advance. Our p u r p o s e curiosity, knowledge, improvement in our teachingwas made clear t o the plant administration. And they made our visits very fruitful. We took a great deal back t o the classroom and our departure from the textbook was reflected in our teaching. I recommend this scheme t o teachers generally and to physics and chemistry teachers particularly. So much of the technological world is bidden from our sight when we are bound t o classroom and text.
T o the Editor: Doody and Gibbem (THISJOURNAL, 31, 11 (1954)) state, "The first report or two are liable t o be awkward and stilted." Ain't it the truth!
