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The electric charge on the alpha-rays emitted in a second by a gram of radium
39 °
CURRENT TOPICS.
[J. F. I.
T h e Electric Charge on the Alpha-rays Emitted in a Second b y a G r a m of Radium. H. JEm~ZEJOWSKL (Comptes Rendus, June 20, I 9 2 7 . ) - - T h e number of ~-particles ejected from one gram of radium in a second is a quantity that appears in several calculations of radio-activity, such as those relating to the amount of energy produced in a second and the quantity of helium resulting from atomic disintegration. While numerous experimental measurements of this nmnber have been made, there still exists an uncertainty in its value amounting to several per cent. At the suggestion of Mine. Curie the author has undertaken to find the total electric charge on the ~-particles emitted in a second by I g. of radium. Since each particle carries a charge of two times the fundamental electrical quantity, 4.774 electrostatic milts, the number of ~-particles is obtained by dividing the total emitted charge by the charge on each particle. The ~-particles emitted by a radium source of clearly determined position pass through a diaphragm and fall on an electrode joined to an electrometer from which the total charge received can be found. To avoid the disturbance of ionization currents a high vacuum was maintained so that there would be almost no gas to be ionized. Both fl- and 8-rays were deviated from the electrode by a magnetic field. A device was applied for shutting off the ~-rays by a thin laver of aluminum, so that the residual effect of whatever fi-rays reached the electrode and of the photo-electric effect on the electrode due to -/-rays might be determined and eliminated. Provision was made to extinguish any effect of radio-active recoil. The average of thirteen experiments gave as the electric charge emitted by I g. of radium in ~ sec. 33-4 electrostatic units. From this is derived the number of particles ejected by the same source in ~ see., 3.50 x IO~°. This is in good agre4ment with what Geiger and \Verner found by methods of direct counting, but is less than the result of Hess and Lawson, 3.72 x lo ~°. G.F.S. V i t a m i n C in Pears.mVERRAL C. CRAVEN and ~IARTtIA ~,~.
KRAMFR, Of the Kansas Agricultural Experiment Station (Jour. Agric. Research, I927, 34, 385-392), have studied the occurrence of the anti-scorbutic vitamin, water-soluble C, in pears, using guineapigs as experimental animals. The animals were protected from scurvy by a daily dose of between IO and 15 grams of raw pear. The raw pear had approximately 25 per cent. of the anti-scorbutic potency of orange juice. The anti-scorbutic vitamin of pears was completely destroyed hy the open-kettle method of home can~ing, and was partially destroyed by the cold-pack method of home canning; it was not influenced by storage of the raw fruit at a temperature of 4 °° F. J . S . t-I.
CURRENT TOPICS.
[J. F. I.
T h e Electric Charge on the Alpha-rays Emitted in a Second b y a G r a m of Radium. H. JEm~ZEJOWSKL (Comptes Rendus, June 20, I 9 2 7 . ) - - T h e number of ~-particles ejected from one gram of radium in a second is a quantity that appears in several calculations of radio-activity, such as those relating to the amount of energy produced in a second and the quantity of helium resulting from atomic disintegration. While numerous experimental measurements of this nmnber have been made, there still exists an uncertainty in its value amounting to several per cent. At the suggestion of Mine. Curie the author has undertaken to find the total electric charge on the ~-particles emitted in a second by I g. of radium. Since each particle carries a charge of two times the fundamental electrical quantity, 4.774 electrostatic milts, the number of ~-particles is obtained by dividing the total emitted charge by the charge on each particle. The ~-particles emitted by a radium source of clearly determined position pass through a diaphragm and fall on an electrode joined to an electrometer from which the total charge received can be found. To avoid the disturbance of ionization currents a high vacuum was maintained so that there would be almost no gas to be ionized. Both fl- and 8-rays were deviated from the electrode by a magnetic field. A device was applied for shutting off the ~-rays by a thin laver of aluminum, so that the residual effect of whatever fi-rays reached the electrode and of the photo-electric effect on the electrode due to -/-rays might be determined and eliminated. Provision was made to extinguish any effect of radio-active recoil. The average of thirteen experiments gave as the electric charge emitted by I g. of radium in ~ sec. 33-4 electrostatic units. From this is derived the number of particles ejected by the same source in ~ see., 3.50 x IO~°. This is in good agre4ment with what Geiger and \Verner found by methods of direct counting, but is less than the result of Hess and Lawson, 3.72 x lo ~°. G.F.S. V i t a m i n C in Pears.mVERRAL C. CRAVEN and ~IARTtIA ~,~.
KRAMFR, Of the Kansas Agricultural Experiment Station (Jour. Agric. Research, I927, 34, 385-392), have studied the occurrence of the anti-scorbutic vitamin, water-soluble C, in pears, using guineapigs as experimental animals. The animals were protected from scurvy by a daily dose of between IO and 15 grams of raw pear. The raw pear had approximately 25 per cent. of the anti-scorbutic potency of orange juice. The anti-scorbutic vitamin of pears was completely destroyed hy the open-kettle method of home can~ing, and was partially destroyed by the cold-pack method of home canning; it was not influenced by storage of the raw fruit at a temperature of 4 °° F. J . S . t-I.