The choice of chlorine as a part of this system was brought about by the fact that ethylene and chlorine combine readily and form ethylene chloride. It will be noticed that the initial electromotive force in all three experiments is approximately nine-tenths of a volt. The system remained fairly constant under uniform conditions. In order to find out if this observed E. M. F. was due to the presence of oxygen or hydrogen in the C2H4, oxygen was allowed to flow into the system in a volume equal to that of the ethylene and we noticed a dropping off of the potential, as we should expect. This 1 The ethylene gas was entirely shut off and only oxygen allowed to flow in. 2 Oxygen stopped entirely and only ethylene entering. case is observed in Table I, Note I. The same table shows the rise and fall of the potential as the amounts of oxygen and ethylene are varied (Notes 2, 3, 4, 5). The same fact is more distinctly noted in the case of Table II, Note 1, where the E. M. F. becomes very small. It is noticed in this table that the E. M. F. increased as soon as the flow of oxygen was stopped and "pure" ethylene was allowed to bubble in, and that the system returned quite rapidly to its normal value. Table III shows an experiment in which ethylene is used against chlorine, and the E. M. F. remaining fairly constant at approximately 0.9625 volt. These experiments show apparently that ethylene gas when used in a gas electrode sets up an electromotive force of considerable amount and probably proceeds in a manner described below. As analysis of the ethylene showed that it is not absolutely pure, the next phase of our work will be to prepare the pure gas free from hydrogen, oxygen, ethane, etc., in order to prove beyond any question that pure ethylene gives the electrode described above. The object of these studies is to learn whether ethylene combines with chlorine, bromine, hydrogen, etc., through an electronic transfer which can be used to develop an E. M. F.; as the preliminary study is certainly in harmony with this idea we may interpret the reaction as follows for the present: + + CH2 = CH2+ Cl2 →→ CH2 CH, + 2C1 − Summary CH,C1−CH,CH The work which has already been carried out on the study of the ethylene electrode indicates that it is an entirely new system; that it is a system possessing a very high electromotive force; that it is easily reproducible and constant as illustrated by the three separate tables submitted. Furthermore, it is apparent that chemically pure ethylene is difficult to prepare. Finally, the theory of its action as a gas electrode involves the idea that the ethylene loses two electrons to the electrode and then combines with the chloride ions. Department of Chemistry of Forest Products, STUDIES IN OXIDATION AND REDUCTION1 BY W. F. CLARKE, C. N. MYERS AND S. F. ACREE The Electromotive Force of the Reaction HCHO HCOOH Qualitative. Many of the ordinary reactions which we observe each day serve as excellent examples for the study of electromotive force. The work of Acree and his co-workers leads the student of chemistry to regard the common reactions more carefully in accordance with the theory of ionic and molecular reactivity. The physical chemist should no longer believe that only ions participate in each reaction. The theory of Arrhenius and later workers taught us that the ions were the carriers of electrical charges and that it was their function to bring about chemical change. Accepting this view as a partial explanation and adding to this the newer conception of Acree in which the nonionized salts are regarded as an important factor in reactions, might we not suppose that the nonionized part carries a part of the electrical charge in an equilibrium phase such as: NaOC2H5 + IC2H5 + NaOC2H5 + IC2H5 →→ C2H2I.NaOC2H, or CH, + INaOC2H, →→ NaI + (C2Hs)2O Without doubt electromotive force work will aid in studying these rapidly changing systems and complexes, and the accuracy and rapidity of this kind of method will greatly help the investigator to measure these values. In making a study of this reaction, it is necessary to have a U tube of the type described under the subject of the ethylene electrode. The electrolyte used in this experiment was N/5 sodium hydroxide. The oxygen used in the oxidation experiment was obtained by the electrolysis of barium hydroxide. The electrodes consisted of two platinum electrodes of the same type as used in the hydrogen electrode work, one in each arm of the U tube. Oxygen was allowed to bubble against one of 1 Contribution from the Chemical Laboratory of Johns Hopkins University. the electrodes, and the electromotive force of this element was, therefore, that of a concentration element in which the oxygen on one side is about five times as concentrated as on the other. The concentration pole was positive. The above table shows that the E. M. F. for the system is practically constant. The study of the oxidation is now ready. One drop of a forty percent solution of formaldehyde is added to the sodium hydroxide solution on the side opposite to the one into which oxygen is bubbling. The value for the electromotive force immediately increased and reached a constant value. Three drops more of formaldehyde were added and an additional increase of the E. M. F. was observed. At this point air and carbon dioxide were blown through the solution, so that an idea of what effect blowing the formaldehyde out of the pipette had on the electromotive force. The reading dropped off to 0.505, showing that the result was not very large. Theory of the reaction: HCHO+ O- HCOOH It is well known that aldehydes are easily hydrated and possess acid properties. In the presence of an alkali, NaOH or KOH, we would have the sodium or potassium salt formed as: H H-C-OK OH When oxygen goes into solution at the anode, it reacts with HOH and takes up negative charges from the electrode for each atom of oxygen going over into the form O → 2(OH). For every two (OH) ions that go into solution, two (OH) ions are discharged at the other pole in the reaction. We do not attempt at this time to give any details of the reaction. The object of this investigation is to determine whether the anion or molecule, or both, of the salt A is oxidized, and to learn the real mechanism as completely as possible. Now that a constant E. M. F. can be obtained we shall begin these studies quantitatively. On the Oxidation of Phenolphthalin to Phenolphthalein C6H4OH C6H4OH + H2O. C-O CHOH |