Evening star., 1921-04-10

| invisible except with q magnifyine
glass. and this enables the owner to
| identify the specimen.
"If a thief should crack the tube and
pour the powder into his hand. actua
contact with the gram of raduin
/, for, a few minutes only would from
| the resulting burn, reduce that mem
! Der to a SCARED and useless ap-
pendage in the course OF ie"
| weeks.
."Au this renders it very improbable
| that Nine. Curie will carry her S1OV:'
| coo treasure in her vanity bag. She
! will place IT as quickly as possible lr
a safe deposi: vault. and Will trans
! init it to her laboratory In Perls o9
express.
so much for the way in Whici i,
testing of it after purchase Will be
done by the bureau OF standards. IN
Washington, and is a very interest
ing process. Radiun as sold is never
pure, but is a mixture OF radiuH
salt-usually the sulphate-with pa
rum sulphate, and sometimes trace
OF mesothorium. The labor of sepa-
rating the barium from the radium
completely is so great that perhaps
only a few chemists in the world
have ever seen pure radium salts
Nine. Curie herself having been the
frst to prepare the pure product. II
/ is. therefore. impossible to weigh ou1
exact amounts of radium salts, but
| inasmuch as the contaminating SUD
stance does not in any way alter the
radium for experimental use. or in
| the treatment OF cancer, the presence
| of a small amount of impurity does
no harm
Tested by Light.
| Instead of being weighed, then
oh h r.
it gives off This may sound strange
Of New York is officially tested by
the amount Of light which it gives
| in comparison with standard can
| die. no attention being paid to tht
chemical composition of the gas Sc
radium is measured by the s, iisn, Ign
| being a known quantity Of radium
| The first Of these known quantitie:
was prepared by Nine. Curie, sealed
! in glass tube, and deposited ir
! the bureau Of weights and measure,
ments in Paris. Just as the stahdart
| standards at Washington and the
! standard meter at the bureau ir
Paris From this standard so-callee
! secondary standards are made b,
comparison with the original tube
prepared by Nine. Curie. Such a sec
y
| ington. sealed up and used only tt
measure radiun.
| "Now radium gives of three kind:
! Of rays. two Of which are high-sp
particles and the third Of which i:
light. This radium light is invisible
! because the human eye is not sensi'
tive to it. So. instead OF measuring
| the radium against a standard candle
! we measure 1t against the II ght giver
! off by a standard amount OF the sub
| stance. When the radium light passe:
| through air It causes a change il
/ the air PARTICLES. so that an elec
| ttical current can pass and thu
| amount Of this electrical current i!
in exact proportion to the quantit,
| OF radium. To remove the high -spe et
particles which interfere with tn,
| test the radium Is placed in leat
box. with walls about half an incl
| thick. in which they stick.
! Half an inch Of lead may seem {
| lot, but some Of the particles from
| radium are really high speed. For in
| stance. IL boy should throw bas'
ball directly west with the speed o
one Of these particles. IT would e.
\ Ground the world and hit in the bach
] Of the head in exactly one-eighth Of ;
| second. while the fastest r,iie bulie
| would take twenty hours to do thu
! same thing.
! Electricity Ia Measured.
| "The light rays from the radium
! however, pass through this lead ant
| strike the air in another little boz
! which is connected with a very sen
sitive machine for detecting electrica