Measurements of total nuclei, of uncharged nuclei, and of large ions in the free atmosphere at Washington, D.C

In July and August, 1931, observations were made on the total and uncharged condensation‐nuclei in the free atmosphere on the grounds of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, in northwest Washington. The nuclei were measured before and after passing through a large‐ion counter between the tubes of which sufficient potential was applied (about 900 volts) to remove all charged nuclei with mobility of 1/3000 cm per second per volt per cm. From 21 sets of measurements, the ratio of uncharged to total nuclei (N0/NA) is found (after applying corrections for loss of nuclei while passing through the apparatus) to be 0.66, the mean value of N0 being 6,300 and the computed value of NA being 9,500. With potentials of 535, 890, and 1890 volts interchanged on the large‐ion tubes, practically no change occurred in No/NA, showing the mobility of the large ion to be not less than 1/1700 cm per second per volt per cm. In October and November, 1931, 77 measurements were made with the large‐ion counter on the number of electronic charges of one sign (positive and negative alternately) per cc in the atmosphere, simultaneously with measurements of total and uncharged nuclei. Small ions were removed from the air entering the large‐ion counter by a small‐ion counter attached to the intake. From these data N0/NA is 0.72, N±/NA is 0.14, N0/N± is 5.8 and the charge per large ion 1.10, the last figure being in good support of the generally accepted view that each large ion carries only one electronic charge. It is seen that NA = N0 + 2N±. The values of N0 and NA are more than double those found in July and August, being 15,000 and 21,000 nuclei per cc, respectively. These results are compared with the work of J. J. and P. J. Nolan, Scholz, Hess, and Israël, and evidence is found for believing that the ratio N0/NA increases in magnitude with increasing nuclei‐content of the air. A quite different analysis of the data obtained in October and November than was made for the above results is undertaken on the basis that N±/NA is not 0.14 but has instead two values, since 23 individual values fall closely around 0.20 and the remaining 54 around 0.10. The immediate conclusion is that the nuclei are at times doubly charged. From this point of view, the data are retabulated and re‐examined and it is found that the results do not show any inconsistencies which would preclude the possibility that doubly‐charged large ions were present almost exclusively on certain occasions and singly‐charged ones almost exclusive on other occasions during the observations here discussed.