mycLn-rieh lilt rate i> admixed with art 1-vated carbon on a continuous basis. T h e carbon is introduced by a measuring mecha-

,sm which integrates the amount of carbon added with the flow of broth fill ra te and the streptomycin concentration in t he filtrate. The introduction of carbon must be very closely controlled, as insufficient carbon results in incomplete adsorption and excess carbon reduces the elation yields. The strcptoinycin-rich carbon is separated from the spent broth by filtra­tion. The spent broth has a very high biological oxygen demand, and it is d is ­posed of by quadruple effect evaporation followed by inciner.-it ion of the resulting concent rate.

Following separation from the spent broth, the rich charcoal adsorbate is washed first with alcohol and then eluted with acid-alcohol so hit ion. The acid eluate is neutralized and the streptomycin con­centration in soluti'-n has now been in­creased to 0. lO to O.LV, and con. iderable preliminary purification has taken place.

Evapora tion of Neutral El note

The neutral eluate is now concentrated to a solution from which the streptomycin

Scaborg Announces Fissionable Neptunium Tlav discovery of a fissionable isotope

of neptunium was announced by Glenn T. Seaborg, professor of chemistry at the University of California, at a meet­ing of the California Section of the AMKRICAX CMJVMICAL SO<II;TY on Octo­

ber 14. The new isotope, Xp'-:57, under­goes fission upon bombardment with slow neutrons, but the number of atoms which split in any given quantity is so low that it could not be used in atomic bomb>, according to Dr. Scaborg.

Xp237 was first produced in MM2 by Dr. Seaborg and Arthur- 0. W'ahl in the (>0-ineh cyclotron at Berkeley, but its fissionable tendency and low fission cross section (2 X 10 2G sq. cm.) were discovered by A. (Jhiorso, D. "W. Osborne, and L. H. Magnusson, work­

ing; with Dr. Seaborg at the iikotallur-gical laboratory, University olChicngo. \"p-'17 is among the by-products of p lu -'oniuni production a< the Clinton a n d ITanford plants.

Dr. Senborg also reported the d is ­covery of a new isotope of plutoniuni-, Pu241, and announced the mass n u m ­bers of the elements, ainericium a n d curium. Pu- '1 i- produced by a lpha particle bombardment ofl~- : i\ It h a s a relatively long half-life and l'< >rms an isotope of ameiMciuni by beta-csiiission.

Am211 (element 95) is an a lpha-emitter and has a half-life of ,")(K) years . Curium (element 00) has two alphit-emitt ing isotopes, with mass intunbers 240 and 242. Their half-lives are one month and five months, respectively.

can be precipitated by solvents as the crude hvdrochloride and be recovered

Above. Fermutilation unit in the plant at Flklon. \a. Slreptoniyces griseus. J'roni ivliich the drug is produced, is grown.from lust-tube tpuin lilies through increasingly larger tanks. When it has multiplied itself billions of times, the living material is transferred to the huge tanks shown above for final ferrnen tation. Beloiv. Filtration units used to remove the insoluble mycelium from

fermented solutions of tJie crude drug

with high yield. The c.onci'mtration is made by a series of stops employing single pass, long tube evaporators, The tem­perature of evaporation is critical and must be carefully controlled as strepto­mycin becomes increasingly more unstable with rising temperature and concentration. These low operating temperatures require vacuum evaporation, which in tu rn makes the problem of solvent recovery increas­ingly difficult.

Purification arid FinaI Concentra tion

The crude streptomycin is finally pre­cipitated from t h e resulting 'concentrate b y addition of a suitable solvent. After filtration and drying, the crude material is ready for final purification. At this point in the process, t h e streptomycin is 25 to 30 f 7 pure.

The crude streptomycin is now carried through a long series of purification steps in which pyrogens and other toxi<; or undesirable constituents in the crude product are eliminated. Finally, the clinical streptomycin is recovered a s a dry, sterile, hygroscopic, white powder.

Literature Cited

(1) Brink, N. GM Kuehl, F. A., Jr., and Folkers, K., Science, 102, 506 (1&45).

(2) Kuehl, F . A., Jr., Flynn, IS. H., Brink, N. G., and Folkers, K., ./\ Am. Chem. Soc.t 68 (in press) (19405.

(3) Kuehl, F . A., Jr., Flynn, E. H. t Holly, F. W., Mozingo, R., and Folkers, K., Ibid., 68, 536 (1946).

(4) Peck, R. L., Graber, R. P., Walti, A., Peel, E. W., Hoffhine, C E., Jr . , and Folkers, K., Ibid., 68, 20 (1946).

(5) Scliatz, A., Bugie, E., and Waksmau, S. A., Proc. Soc. Expt. Biol. Med., 55, 66 (1944).

(6) Waksman, S. A., and Schutz, A., ./'. Am. Pharm. Assoc. (So. EcH.), 34. 273 (1945).

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