PHYSICS ARTICLES DISCUSSION FORUM
A few months ago, K. Peters and I published an account of experiments we had made in an attempt to transmute hydrogen into helium ("Ber. d. Deutschen Chem. Ges.",(vol) 59, 2039, 1926). A more or less detailed account of this publication appeared in the columns of Nature (vol. 118, p. 526, 1926), and perhaps I may be permitted to refer to a more recent publication on the same topic by K. Peters, P. Gunther, and myself ("Ber. d. Deutschen Chem. Ges.", (vol) 60, 808, 1927). In this communication, as a result of further experiments, we feel that we are in a position to give an explanation of the occurrence of the observed very small quantities of helium in our experiments, without having recourse to the assumption of a synthesis of helium.
In the first-mentioned communication we considered the penetration of helium from the atmosphere through the glass walls of the apparatus to be the most likely source of trouble in such experiments, and we excluded this possibility by the use of vacuum jackets, immersion in water, and similar devices. In addition, we also discussed the possibility of regarding the helium dissolved in the glass as an explanation of the observed effects, but blank experiments led us to the conclusion that the quantity of helium capable of being liberated in this way was beyond the limits of sensitivity of our method of detection. In the interval we have carried out experiments both in the Baker Laboratory of Cornell and in the Chemical Laboratory of the University of Berlin, and these have shown that the liberation of helium from glass (and from asbestos) is dependent on the presence of hydrogen. Thus glass tubes which gave off no detectable quantities of helium when they were heated in a vacuum or in oxygen were found to yield helium in quantities of the order of 10-9 cc when they were heated in an atmosphere of hydrogen. Now in the earlier experiments the glass tubes containing palladium yielded helium, whereas the empty glass tubes used in control experiments did not; and since the former tubes would fill hydrogen on the application of heat, we see that the source of helium lay not in the palladium but in the glass, in spite of appearances to the contrary.
Our method of detecting helium is sufficiently sensitive to show that a glass tube which has been completely freed from its content of helium by heating in hydrogen takes up a detectable amount of neon-free helium from the atmosphere even after only one day's contact with the air.
Since asbestos behaves similarly to glass, we now see why one particular palladium preparation, bought as palladium-asbestos, yielded large quantities (10-7 cc) of helium after being charges with hydrogen. Here, obviously, in contrast to the preparations we made ourselves, the asbestos had not been ignited until it was free from helium, and a fraction of the residual helium was always liberated by heating when the palladium was charged with hydrogen, whereas in oxygen no development of helium could be observed.
As a result of our more recent experiments we have thus established that, in using an apparatus made of glass, one cannot make any trustworthy statement as to the origin of 10-9 cc of helium if air comes in contact with the apparatus, parts of which are later heated in hydrogen. By avoiding all heating of the apparatus, we shall endeavor to decide whether a transmutation of hydrogen into helium of the order of 10-9 cc or less takes place. In any case, the amount of helium formed in experiments on electric discharges, as tested by various workers and by ourselves, and in experiments on the action of palladium, does not reach the order of magnitude of 10-8 cc.
It is scarcely necessary to emphasize the fact that the sensitiveness of our method, though limited to 10-8 cc, is sufficient to decide with certainty the other questions dealt with in our first communication, such as the helium content of meteorites, the helium development of radioactive deposits, and so on.
Fritz Paneth, Berlin, Mar. 2
The transmutation of Hydrogen into Helium, epilogue
Epilogue to article by F. A. Paneth and K. Peters and published in Nature, Berlin March 2 1928.
A few months ago, K. Peters and I published an account of experiments we had made in an attempt to transmute hydrogen into helium ("Ber. d. Deutschen Chem. Ges.",(vol) 59, 2039, 1926). A more or less detailed account of this publication appeared in the columns of Nature (vol. 118, p. 526, 1926), and perhaps I may be permitted to refer to a more recent publication on the same topic by K. Peters, P. Gunther, and myself ("Ber. d. Deutschen Chem. Ges.", (vol) 60, 808, 1927). In this communication, as a result of further experiments, we feel that we are in a position to give an explanation of the occurrence of the observed very small quantities of helium in our experiments, without having recourse to the assumption of a synthesis of helium.
In the first-mentioned communication we considered the penetration of helium from the atmosphere through the glass walls of the apparatus to be the most likely source of trouble in such experiments, and we excluded this possibility by the use of vacuum jackets, immersion in water, and similar devices. In addition, we also discussed the possibility of regarding the helium dissolved in the glass as an explanation of the observed effects, but blank experiments led us to the conclusion that the quantity of helium capable of being liberated in this way was beyond the limits of sensitivity of our method of detection. In the interval we have carried out experiments both in the Baker Laboratory of Cornell and in the Chemical Laboratory of the University of Berlin, and these have shown that the liberation of helium from glass (and from asbestos) is dependent on the presence of hydrogen. Thus glass tubes which gave off no detectable quantities of helium when they were heated in a vacuum or in oxygen were found to yield helium in quantities of the order of 10-9 cc when they were heated in an atmosphere of hydrogen. Now in the earlier experiments the glass tubes containing palladium yielded helium, whereas the empty glass tubes used in control experiments did not; and since the former tubes would fill hydrogen on the application of heat, we see that the source of helium lay not in the palladium but in the glass, in spite of appearances to the contrary.
Our method of detecting helium is sufficiently sensitive to show that a glass tube which has been completely freed from its content of helium by heating in hydrogen takes up a detectable amount of neon-free helium from the atmosphere even after only one day's contact with the air.
Since asbestos behaves similarly to glass, we now see why one particular palladium preparation, bought as palladium-asbestos, yielded large quantities (10-7 cc) of helium after being charges with hydrogen. Here, obviously, in contrast to the preparations we made ourselves, the asbestos had not been ignited until it was free from helium, and a fraction of the residual helium was always liberated by heating when the palladium was charged with hydrogen, whereas in oxygen no development of helium could be observed.
As a result of our more recent experiments we have thus established that, in using an apparatus made of glass, one cannot make any trustworthy statement as to the origin of 10-9 cc of helium if air comes in contact with the apparatus, parts of which are later heated in hydrogen. By avoiding all heating of the apparatus, we shall endeavor to decide whether a transmutation of hydrogen into helium of the order of 10-9 cc or less takes place. In any case, the amount of helium formed in experiments on electric discharges, as tested by various workers and by ourselves, and in experiments on the action of palladium, does not reach the order of magnitude of 10-8 cc.
It is scarcely necessary to emphasize the fact that the sensitiveness of our method, though limited to 10-8 cc, is sufficient to decide with certainty the other questions dealt with in our first communication, such as the helium content of meteorites, the helium development of radioactive deposits, and so on.
Fritz Paneth, Berlin, Mar. 2