luly,
ANALYTICAL EDITION
1946
41s LITERATURE CITED
with such factors as pH and coiicentrittioti. the conditions of the iletermination must be rigidly standardized, and any departurr ‘rcim these conditions should be noted in expressing results. The (.alcium value obtained may have little connection Jvith u-ater-oftenirig power under conditions of uce other than those of the riiethod Where performance under conditions of actual use is (ecluired, the method may be modified, but only with the under-tanding that the resulting data vannot be compared directly with data ohtained by using thr rnvthod :iq writtpn.
(1) .Indress, K. K.,
wiist,
K., Z. anorg. allgem. C hem., 237, 113
(1938). ( 2 ) Chw-ala, S.. aiid Martina, A , . Mllellicind Trrtilher.. 21. 285. 464 (1940) (3) Huber, H A ~ L Q CC‘hem., Z L . 50, 323 (19371. (4) Moran. H. F., ISD E N G CHEM.,ANAL.E D . , 15, 361 (19431. (5) Rudy, H . , Srhloesaer, H . , and j%-atzel, R . A n g e l , . C‘hem 53 525 ( 1 9 4 0 ) . (61 Watzel. R.. 7)7e (’hemie, 55, 356 (1942)
.
.
Radioactive Studies A n a l y t i c a l Procedure for Measurement of Radioactive A r s e n i c
of
90-Day
F. C. HENRIQUES,
JR.2,
Half-Life’
AND
CHARLES MARGNETTI3
Harvard University Chemical Laboratories and Medical School, Cambridge and Boston, Mass.
A procedure for the quantitative radioactive analysis of arsenic of 90-day half-life depends upon the isolation of arsenic metal by reduction with hypophosphite, collection on a Solar filter plate, and measurement of the activity inside the chamber of a Lauritzen elec4roscope. The utilization of 90-day arsenic rather than the 16-day ‘isotope extends considerably the duration of experimentation following cyclotron bombardment.
DI
RIKG the course of inveatigationb utilizing 1G-day a* a tracer, it was found that an appreciable amount of radioactivity due to 90-day arsenic is also present. This long-hved waenic ( 2 ) is known to be either -W2or As73. I t disintegrates into Ge’2 7 3 by the capture of a I
