CHAPTER V. FIGURE 1. Condensation chamber, R; exhaustion reservoir, B, and appurtenances. Scale 1/9. FIGURES 3, 3'. Diameter of cloud particles (cm/103) and supersaturation for HCl.. PAGE 95 95 113 113 113 113 113 113 113 113 113 113 113 FIGURE 11. Number of particles lost in the lapse of minutes for CaCl,. Bulks, 500 and 1000 cub. cm., respectively..... 113 ....120, 122 FIGURES 12-15. Number of particles, n, and their absorption velocity, k, generated by shaking solutions of different solutes and of different logarithmic concentrations (log c)....... FIGURE 16. Nucleation produced under like conditions of shaking in different solutions of the same concentration ..... 122 124, 125, 126 FIGURES 17-19. Loss of nuclei in the lapse of minutes for different solutions.. FIGURE 20. Diagram showing the relation of vapor pressure to the radius of the nucleus for different strengths of solution..... 135 CHAPTER VI. FIGURE 3. Tubulated partition for diffusion of water nuclei... FIGURE 1. Diffusion tower, AB; exhaustion chamber, C'; desiccator, D, and appurtenances.. 143 144 144 FIGURE 4. Rise of nucleation in the lapse of minutes (diffusion upward) in benzol.. FIGURE 9'. Rise of nuclei in the lapse of 50 min..... FIGURE 1. Electrometer showing capsule, needle, and quadrants in place. Sectional elevation... 164 164 THE STRUCTURE OF THE NUCLEUS, A CONTINUATION OF EXPERIMENTS BY CARL BARUS, HAZARD PROFESSOR OF PHYSICS AT BROWN UNIVERSITY. CHAPTER I. ON THE EFFECT OF TEMPERATURE AND OF MOISTURE ON THE EMANATION OF PHOSPHORUS, AND ON A DISTINCTION IN THE BEHAVIOR OF NUCLEI AND OF IONS. INTRODUCTION. 1. Object, etc.-Endeavoring to differentiate the properties of the nucleus and the ion, it occurred to me that the effects of temperature, when worked out simultaneously by the volumetric and by the electrical methods, would probably present a contrast. If the two functions relating to condensation and to electrical conduction are different, then their thermal variations are not likely to be the same. The temperature which insures the maximum production does not also necessarily insure maximum instability. The results of the following paper bear out this surmise. Again, if phosphorus is to be used as an ionizer, some definite knowledge as to the cause of its variable intensity is essential from a practical point of view. The substance is so remarkably adapted for the purpose in many ways, that the endeavor to put it in control quantitatively is well worth while. This too, I think, has been accomplished. Finally, I have shown that the low number of ions (n=8x101 per cubic centim.) in the saturated phosphorus emanation, found from the experiments with the tubular condenser, is due to non-saturation. I have been able to nearly double this number, putting these results in accord with the data of plate and spherical condensers. Incidentally, certain curious conditions under which the emanation produces permanent conduction in the condenser are identified with the occurrence of traces of moisture. This behavior so closely resembles the effects of radio-activity that the extreme caution needed before such a property can be predicated becomes apparent. VOLUMETRIC COMPARISONS. 2. Apparatus.-The apparatus to investigate the relation of the emanating activity of phosphorus to temperature is shown in figure 1, the thermal part consisting of a coil of thin lead pipe (1/8 inch bore), L, submerged in a large water bath of copper, AB, 13 centims. high, 15 centims. broad, and 20 centims. long. There were 21 turns of lead pipe, each turn 6 centims. in diameter. The air coming from the gasometer train by way of a desiccator beyond D, and a stop-cock, F (fine screw valve), traversed this considerable length of slender tubing, fully taking the temperature of the water bath, thereafter to be discharged into the central straight pipe of brass, ab, 1.2 centims. in diameter, containing the ionizers (not shown). The charged air is finally conveyed into the influx pipe of the color tube, C, by the removable short neck, G. A ther dmometer, t, is placed in the water bath; another may be inserted into the end, b, through a perforated cork, so as to be in contact with the ionizers. FIG. 1. APPARATUS FOR HEATING NUCLEATED AIR. FIG. 2.- - SECTION OF THE TUBULAR CONDENSER SHOWING Care was taken that all changes of temperature should be slow. Thus it took 3 hours for the temperature to rise from 5° to 13° in the following experiments, for instance. The ionizers, as usual, were strips of wire gauze, holding thin pellets of phosphorus between them. They were inserted into, or removed from the tube, ab, through b. If saturation is aimed at, an excess of freshly cut phosphorus surface should be used. This was only done when specially called for in the present work, where the form of the temperature function is the chief consideration. 3. Method and data.-The method of experiment usual in my work was adopted, the liters per minute (d V/dt) of saturated phosphorous air necessary to produce the fiducial blue of the color tube being observed at different temperatures. The data are given in table 1, in the first part of which observations for falling temperature, and in the second for rising temperature, are recorded. The pressure of the steam jet was about p= 4 to 6 centims. The inflowing air showed a temperature of 27° to 28°. The table contains some other colors (including orientation. opaque) for TABLE 1. 3 -EFFECT OF THE TEMPERATURE OF PHOSPHORUS ON ITS EMANATION. 4-5 cm. ; AIR TEMPERATURE, 27-28°. WATER BATH METHOD WITH STEAM JET. = The chief data of the table are reproduced in the chart figure 3, and show the sudden cessation of reaction at 12°-13°. 4. Discussion. For the sake of preliminary comparisons with the corresponding electrical charts given below, it is well to lay off 1/(d V/dt) in its variation with temperature: for this reciprocal runs parallel to the concentration of the emanation producing the color. The construction is given in figure 4, in which the sudden rise of activity in producing nuclei is apparent at 13°, and the subsequent gradual decline thereafter as far as examined is again manifest. Anticipating data of subsequent paragraphs I may add that the maximum ionizing activity is at 20°, showing the two thermal relations to be non-coincident. The charts show in the first place, that as temperature falls from the highest admissible values, say 35°, the emanation of phosphorus actually increases,' at a rate This increase may be due to the gradual thorough desiccation of the phosphorus by the dry current of air. The grids were not dried preliminarily over calcium chloride. 2 of about 2 per cent, per fall of 1° C. The maximum activity occurs at about 13°, and is upwards of 25 per cent. greater than at 30°. Between 12° and 13°, however, the emanation is quenched at an enormously rapid rate, falling just short of suddenness. Practically, therefore, the reaction begins at about 13°, with full if not greatest intensity. Below 12°, the emanation is insignificant and the maximum permanent colors obtainable are faint blue grays, even when the gasometer flow is forced to, say, 400 FIG. 3.--DEPENDENCE OF THE RECIPROCAL NUCLEATION RATE (dVdt) ON TEMPERATURE. FIG. 4.-DEPENDENCE OF THE NUCLEATION RATE (dt/dV) ON TEMPERATURE. FIG. 5.-COMPARISON OF THE RATES OF ELECTRICAL DISCHARGE AND OF VOLUME EFFLUX. liters/minute. There are no opaques. discernible. Below 10° there are no permanent colors 5. Here, however, and slightly above and below this temperature, definite puffs of color or of darkness are obtained immediately after opening the faucet suddenly. The phenomenon may be repeated indefinitely by closing the faucet for a period of 2-5 seconds (longer at the lower temperature), and then suddenly opening it again. The puffs are at first vaguely recognized at about 8°, or even below. They become more marked as temperature rises. They are still marked at even 12°, when the fainter colors are beginning to be permanent. They show a maximum degree of darkness depending on temperature, beyond which they do not increase even if the cock is closed indefinitely. From a theoretical point of view this result is noteworthy. Below the reaction temperature (say 12.5°), what may be called the vapor pressure of the reaction is a definite quantity, but decreases with temperature at an enormously rapid rate; |