T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
May, 1922
gravitation, capillarity, expansion, etc., and by means of these foreign forces new matter is brought into contact, that the phenomenon is repeated.” Debusas has considered the question of effective collisions and has anticipated some of Langmuir’s views on oriented adsorption. Whenever two mols of peroxide of hydrogen meet in the
position of reaction, then decomposition into water and oxygen will take place, but if they collide in other positions, then they will not decompose. * * * * The decomposition of peroxide of hydrogen into water and oxygen is retarded by some and accelerated by other substances. Platinum, silver oxide, and manganic dioxide, respectively, promote, whilst acids prevent the decomposition. Platinum possesses a great attraction for oxygen, its powder absorbs more than two hundred times its volume of the gas. This attraction is also exerted towards oxygen which is in chemical combination. If now a piece of platinum is placed in peroxide of hydrogen, the molecules of the latter will place themselves in such a position of the surface of the platinum, that one oxygen atom of the peroxide is turned towards the platinum and as near to it as possible. The peroxide is polarized. But this has the effect also of bringing the oxygen atoms of different molecules of peroxide in such close proximity on the surface of the metal that they can combine to form common oxygen, the decomposition of the peroxide into water and oxygen and development of energy being the consequence. The action of the platinum places the molecules of the peroxide in the position of reaction towards each other. The actionsof silver oxide and of black oxide of manganese are similar. There are a couple of interesting cases of what appears to be poisoning of the catalytic agent; but the data are not sufficient t o warrant very definite conclusions.8e Phosgene reacts with water to give carbon dioxide and hydrochloric acid, COC12
+ HzO = COL+ 2HC1.
So far as is known, this reaction is not reversible and it actually runs to an end in presence of an excess of water. In presence of concentrated hydrochloric acid, however, the rate of hydrolysis is practically negligible. Thq most plausible way of accounting for this is by assuming that water and phosgene do not react by themselves and that the reaction takes place solely in contact with the walls of the containing vessel. When these are coated with a film of hydrochloric acid of sufficient concentration, practically no phosgene is adsorbed and no reaction takes place. The, hydrolysis should be studied with different concentrations of hydrochloric acid and with a varying ratio of wall surface to mass of solution. If this explanation is correct, it may account for the rather surprising stability of a phosgene cloud in the damp atmosphere of Flanders, there being no catalytic agent in the cloud t o cause the decomposition of the phosgene. On this basis, a cloud consisting of a mixture of hydrochloric acid and phosgene would be even more stable; but of course this would introduce serious complications in regard to loading. Trimethylchloroformate, ClC02CC13, or superpalite as it is called, decomposes to carbon tetrachloride and carbon dioxide in presence of alumina, c l c o z c c l l = coz
+ cc14,
,
and to phosgene in presence of ferric oxide, ClCO2CC13=2COClz. The reverse reaction has never been made to take place to any measurable extent. During the war some superpalite and ferric oxide were placed in a glass tube connected with a closed manometer. There was rapid decomposition a t first, as shown by the increase in pressure; but, before long, the reaction apparently came to an end. On raising the temperature, the reaction went a little farther and did not reverse when the tempers J . Chem. Soc., 53 (1888),327; Cf. Hufner, J . 9uakt. Chem., [2] 10 (1874), 385; Raschig, 2. angczo. Chem., 1906, 1078; Gillet, Bull. SOC. chim. B e k , SO (1921), 138. 89 Bincroft, Trans. A m . Electrochem. Soc., 36 (1919), 140.
447
ature was brought back to its original value. Since this experiment was not repeated there may be some error in i t and the facts may not be as stated; but i t looks as though the ferric oxide was poisoned and as though the change of temperature modified the adsorption so that more superpalite came in contact with the catalytic agent and was decomposed. If this is the true explanation, it suggests one interesting set of experiments. When ethyl butyrate and water are treated with a small amount of lipase,g0the decomposition proceeds only a little way, owing t o the poisoning of the enzyme by the reaction p r o d ~ c t s . ~ ’It seems probable that with an oscillating temperature it might be possible to carry the reaction much farther with the same amount of enzyme. 81
Kastle and Loevenhart, A m . Chem. J . , 24 (1900),491. Bancroft, J . Phys. Chem., 22 (1918), 40.
(To be continued)
Isotopes By G. M. j.Mackay GERERALELECTRIC C o . , SCHENECTADY, N. Y.
The attention of chemists is called to the remarkable developments which are being made in our knowledge of the fundamental structure of matter and energy. The work of the Cavendish Laboratory in the last few years leaves but little doubt that our complicated system of elements is in reality built up from two simple units, the electron and the proton, the latter being the real unit of mass, the atom of positive electricity, and identical with the nucleus of the hydrogen atom. The work of Rutherford and his associates has shown that artificial radioactivity may be stimulated in the ordinary elements. Hydrogen has been expelled by alpha particles, which are but positively charged helium atoms traveling a t a velocity imparted by 6,000,000 volts, from the atoms of nitrogen, boron, fluorine, sodium, aluminium, and phosphorus. I n many cases this expulsion is accompanied by an evolution of energy, in the case of aluminium of 40 per cent more than that possessed by the helium projectile. Lately, Dr. F. W. Aston, who has been delivering a course of lectures a t the Franklin Institute, has found that most of the elements of fractional atomic weights are really composed of isotopes whose atomic weights are integers to an accuracy of one part in a thousand. At the same time he has found another possible source of interatomic energy. His work is a masterpiece of ingenuity and skilled technic, and is an illustration of the value of tireless perseverance in searching for the meaning of apparently trivial deviations of numerical results from one another. A synopsis of a lecture by Dr. Aston before the local branches of the American Institute of Electrical Engineers and the American Chemical Society a t Schenectady on April 7, 1922, follows: In 1803 John Dalton gave to chemistry what is probably one of the greatest generalizations in its history, the atomic theory. All of his five postulates have since stood the test of over a century of active and unremitting investigation except the one which states that “atoms of the same element are similar to one another and equal in weight.” No direct method was available for testing this hypothesis until 1910, when Sir J. J. Thomson showed that sharply defined parabolic streaks were obtained on a photographic plate when beams of positively charged ions were deflected by means of magnetic and electrostatic fields. This proved that the ratio of the charge of electricity t o the mass of the particle was constant for all the ions forming the parabola, and since the charge was known t o be a definite unit, that the masses of the individual atoms were approximately the same. But the apparatus was not sufficiently accurate to detect small variations in weight.
