An INTRODUCTION
to
the
SYMPOSIUM o n ORGANIC ANALYTICAL REAGENTS* WAYNE E. WHITE UniveHity of Kansas, Lawrence, Kansas
HE TITLE which has been used for our sym- the following classes of organic reagents for inorganic nosmm does not exadlv define the subieds analvsis. A which we are to consider. It seems desirable, Organic solvents therefore, that we first analyze the title; then we may 1. For one or both of the reacting substances. go on with the discussion with clearly defined limita2. To induce and increase precipitation of tions as to its expected scope. water soluble substances. One might conceivably take our title--Organic 3. To extract soluble substances for p+Analytical R e a g e n t s a s applying to reagents for cation of the remaining insoluble mateorganic analysis, in which case the question might rial, or for determination of the extracted arise as to whether the reagents themselves were insubstance. organic or organic in nature. Although a considerati& of special reagents for organic analysis would unB. Organic precipitating aids-where the action is doubtedly be of interest and value, we do not propose not one of displacement from solution as in A, 2, to devote any time to that topic today; our title, then, hut rather of adsorption on the precipitate, refers solely to organic reagents for use in inorganic e. g., the induced flocculation of zinc sulfide by analysis. minute amounts of gelatin as recently reHaving thus limited the field of discussion, it may ported.' be desirable to clarify and classify the contents of this C. Indicatorsacid-base, adsorption, oxidationfield. Wbat various topics might be presented under reduction. the heading "Organic Reagents for Inorganic Analysis?" The answer to this question is determined largely D. Organic primary volumetric standards for by the meaning we give to the word "reagent." A reacidimetry, alkalimetry, oxidimetry. agent is any substance used in the detection or determination of another substance. There is a common E. Organic compounds which serve directly as tendency, however, to restrict the term "any suhreactants in methods of analysis, i. e., reagents stance" in the previous sentence to only those subin the narrow sense of the word. stances which undergo a chemical transformation in the detection or the determination of the other subOf these five groups of reagents, only C, D, and E are stance. The difference between these two interpreta- to receive attention in our symposium and the most tions may be illustrated by the precipitation of cal- emphasis will be placed on Group E. The indicators cium sulfate in a solution containing some ethyl alco- were considered in a symposium held some time ago hol. If calcium were the ion being tested for, then by and therefore need not be reviewed in detail again at the narrower interpretation only the sulfate ion or the this time.% Reasons for, and justification for, particucompound yielding this ion would be considered the lar attention to these organic compounds which may reagent, whereas by the more broad-and correctbe listed under group E of the above classification are definition the alcohol would also be a reagent used in probably apparent to us all. The dream of every the detection of calcium. analyst of having one particular reagent for each eleAdhering to this latter definition we can distinguish ment and radicalreagent which will serve equally well whether that element be in the pure state or in a Introduction to the Symposium on Organic Analytical Remixture of the most complex nature-this dream apagen!s, Kansas City Program, conducted by the Division of Physical and Inorganic Chemistry at the Ninety-first Meeting pears not entirely irrational and unrealizable when we of the American Chemical Society, Kansas City, Missouri, think of the advance which has already been made April 16, 1936. The paper by John H. Yoe, immediately following,was a con- through the application of organic compounds to
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tribution to this symposium. Other of the symposium papers
problems of analysis. We have reagents now which are practically specific, under the proper conditions, for a good many of the metals. In many cases the organic reagents have the further advantage of giving reactions of high sensitivity, sensitivities much higher than any realizable through the use of only inorganic substances, and formerly attainable only by spectrographic means. Most of the very sensitive reactions are those in which distinctive colors are produced. Here, of course, we have the obviously great advantage on the side of the organic compounds, since there are relatively few colored inorganic compounds. Other advantages of the organic reagents will he cited in the papers to follow. I t is not our intention nor desire, however, to relegate to the s a a p heap inorganic chemicals which have
been found useful in analysis; many of the organic reagents are used only in connection with the inorganic, as in lake formation with the hydroxides of aluminum, magnesium, etc. Rather is it hoped that from this symposium there will come a better realization of the value of these special reagents (inorganic, as well as organic) and of the potentialities of research in this field. In this country we are depending chiefly on men like Feigl, Gutzeit, and Hellmnt Fischer of Austria, Switzerland, and Germany, respectively, to give us new reagents and to show us how to use old ones more effectively. American chemistry should contribute more to world progress in this phase of chemistry of such great practical importance to life and industry, as well as to other branches of the physical sciences.
