RADIUM IN WAR
When we remember how all forms of scientific knowledge were called upon
to help in the great struggle, it is not surprising to hear that,
although in a comparatively humble way, Radium has had to do its share.
Now radium is one of the most, if not actually the most, remarkable
substance known. About a generation ago scientific men, or some of them
at all events, were getting rather cocksure. Of course they were quite
right when they realized how much was known about things and what great
strides had been made during the years through which they had lived.
They were proud of the achievements of their scientific friends, for I
am not imputing personal vanity to anyone, and they had reason to be
proud. They made the mistake, however, of thinking that in one direction
at least they had learnt all that there was to be known. The present
generation of scientific men seem to be almost too prone to go to the
other extreme and to dwell rather much on how little we know now and the
wonderful things which are going to be discovered in time.
But that is by the way. A generation ago men seem to have pretty well
made up their minds that they knew all about atoms. They said that
everything was made up of atoms, that the atoms could not be subdivided
nor changed into anything else except temporarily by combination with
other atoms, and that when these combinations were broken up the atoms
remained just as before, quite unchanged. They believed that the atoms
were unchangeable and everlasting. Professor Tyndall, in a famous
address, referred to this in somewhat flowery language, telling his
hearers that the atoms would be still the same when they and he had
"melted into the infinite azure of the past," which a wag translated
into the slang expression of the time, "till all is blue."
Now not very long after Professor Tyndall made this historic speech
Professor Henri Becquerel, of Paris, was trying some experiments with
phosphorescent materials, that is, materials which glow in the darkness.
In the course of these experiments he used some photographic plates upon
which, to his surprise, he found marks which he thought ought not to
have been there. Thinking at first that he had accidentally "fogged" his
plates, as every photographer has done at some time or other, he tried
his experiments again with special care but still he got the mysterious
marks.
Those marks were caused by some of those "unchangeable and everlasting"
atoms deliberately and of their own accord blowing themselves to bits.
For the celebrated Frenchman was not content to let the matter of those
mysterious marks rest: he wanted to know what caused them and he did not
desist until he was on the track of the secret. It appeared after
careful investigation that they were made by the action of something in
some of the ore of the metal "uranium" which he had been using.
Moreover, this something evidently had the power of penetrating through
the walls of the dark-slide to the plate within. Finally, it was tracked
down to the uranium itself which was unquestionably proved to be giving
off something in the nature of invisible light, or at all events
invisible rays, of strange penetrative power. A little later it was
observed that certain ores of uranium seemed to give off these rays more
freely than would be accounted for by the amount of uranium present,
from which fact it was inferred that there must be something else
present in the ore capable of giving off the rays much more powerfully
than uranium can. Madame Curie ultimately found out two such substances,
one of which she called, after her native land, Polonium (for she is a
Pole), and the other Radium. It is the latter which is responsible for
by far the greater part of the rays formed.
The rays are invisible, but they affect a photographic plate in the same
way that light does. They also make air into a conductor of electricity
and if allowed to impinge upon a surface coated with a suitable
substance they cause it to glow.
This spontaneous giving off of rays is now spoken of by the general term
of "radio-activity," and it has grown into an important branch of
science. A number of other substances have been found to exhibit the
same peculiar ray-forming powers, notably Thorium, one of the components
of the incandescent gas mantle by the prolonged application of a
fragment of which to a photographic plate an impression can be obtained
due to the rays.
What, then, are these rays? It is found that they are of three kinds,
not that they vary from time to time, but that they can be sorted out
into three different sorts of rays which are given off simultaneously
all the time.
The first sort are stopped by a sheet of paper, the second passing
easily through a thick metal plate, while the third appear to be
identical with X-rays.
For convenience the three sorts are termed Alpha, Beta and Gamma rays,
respectively, after the first three letters of the Greek alphabet.
Further, the Alpha rays prove to be a torrent of tiny particles about
the size of atoms, indeed if they be collected the gas Helium is
obtained, so that evidently they are helium atoms, and since that is one
of those substances whose molecules consist of a single atom each they
are also molecules of helium. No doubt the reason why they are so easily
stopped by a piece of paper is because being complete atoms they are
large, huge indeed, compared with the particles which form the Beta
rays, for they are apparently those same electrons which are found in
the X-ray tube, and which are at least 2000 times smaller than the
smallest atom.
When the electrons in the vacuum tube are suddenly brought to a
standstill X-rays are given off and in like manner X-rays no doubt would
be given off when they start on their journey, providing that they
started suddenly enough. Hence it is the starting or sudden
explosion-like ejection of the Beta particles which is believed to give
rise to the Gamma rays.
The strength or intensity of the rays can be measured very conveniently
by their action in making air conductive to electricity, for which
purpose a very beautiful but simple instrument called an Electroscope is
employed. It consists generally of a glass-sided box or else a bottle
with a large stopper, consisting of sulphur or some other particularly
good insulator. Through this a wire passes down into the inside of the
vessel terminating in a vertical flat strip to the upper end of which is
attached a similar strip of gold leaf or aluminium foil. Normally the
leaf hangs down close to the strip, but if the wire above the stopper be
electrified by touching it with a piece of sealing-wax rubbed lightly
against the coat sleeve the charge of electricity passes down into the
inside and causes both strip and leaf to become so electrified that they
repel each other.
Owing to the non-conductivity of the air in its normal condition the
leaf will, if the insulation of the stopper be good, remain projecting
almost horizontally for some time until, as it loses its charge by a
slow leakage, it gradually settles down close to the strip.
If, however, a piece of radium be brought near while it is sticking out,
the leaf will fall almost instantly. X-rays have a similar effect even
from several feet or yards away.
The intensity of the radio-activity of different substances can be
compared by noting the difference in the rate at which the leaf falls
under the influence of each.
What is happening, then, to the atoms of radium, which causes them to
show these curious effects and to give off these strange rays? To give
any intelligent answer to that question we are bound to assume that
which the older generation of scientists thought impossible, namely,
that atoms can be broken up. Then we are forced to believe that the
atoms of this particular substance radium are of a peculiarly flimsy
unstable sort, so that they cannot permanently hold their parts together
but are liable to break up, as far as we can see through their own
inherent weakness and under the influence of disruptive forces at work
within themselves.
We must remember, however, that the tiniest speck of matter which we can
see contains a number of atoms of such a size as to be quite beyond the
grasp of our minds. To give a rough idea of it in figures is useless as
no one can comprehend the real value of a figure or two followed by
probably from a dozen to twenty "noughts." It is best to content
ourselves with the general statement that a speck of matter only just
visible to the eye contains an exceedingly vast number of atoms. Of
course a speck of radium is no exception to this and we must remember,
too, that all of them do not break up at once. Indeed, the number
breaking up at any time are actually countable by means of a very simple
contrivance and a sensitive electrometer. Consequently, in view of the
enormous number present and the comparatively small number breaking up
at any moment, it is not surprising to hear that, so it is estimated,
the process can go on for an almost indefinite number of years,
certainly for hundreds. There are, moreover, certain facts which we need
not go into here from which the above fact can be clearly inferred,
quite apart from what has been said about the vast numbers of the atoms.
It seems as if the uranium atoms break up first, giving off helium atoms
and electrons and leaving an intermediate substance called Ionium which
in its turn breaks up giving off the same things again and leaving
radium. That in its turn goes through a complicated series of changes
still giving off the same alpha particles or atoms of helium and
electrons until, it is suggested, it finally settles down into the
simple commonplace metal lead of which we make bullets and water pipes
and such-like ordinary things.
We see then that all through its history--its radio-active history at
any rate--this stuff is throwing off atoms of helium at a very high
velocity (about 50,000 miles a second), and if it be enclosed in
anything this enclosing vessel or substance will be subjected to a
continual bombardment by the alpha particles. Now just as a piece of
iron gets hot if we hammer it, so the enclosing matter is heated by the
continual blows which it is receiving night and day, year in and year
out, from the alpha particles.
Consequently the immediate surroundings of a speck of radium are always
slightly raised in temperature.
Moreover, if a speck of radium be placed against a screen covered with
suitable materials each particle which strikes it will make a little
splash of light. At least that is what it looks like when seen through a
magnifying glass, but to the naked eye there only appears a beautiful
steady glow.
Suppose, then, that instead of putting the speck of radiant matter in
front of a screen we mix it up intimately with a fluorescent substance
such as sulphide of zinc, we then get the same conditions in a slightly
different form. Each particle of the substance serves as a tiny screen
which glows every time a particle hits it. Thus is produced a luminous
paint which glows by night, suitable for painting the dials of
instruments which have to be used in the dark.
No doubt some of my readers will have experienced the strangely mingled
delight and horror of seeing a Zeppelin in the night sky intent on
dropping murder and death on the sleeping civilians of a peaceful town
or city. Some too may have witnessed the later acts in that wonderful
drama, when, beside the silvery monster illuminated by the beams of the
searchlight there must have been, though quite invisible, a little
aeroplane manned by one man or at most two. That aeroplane was, no
doubt, fitted with instruments at which the pilot glanced now and then
and which he was able to see and read because of the tiny speck of
radium mixed into the paint. The little alpha particles gave him the
light by which to see, but they gave no help to the Germans on the
Zeppelin. Hence, in due time he did his work and the gigantic balloon,
the pride of the Kaiser and his hordes, fell to the ground, a blazing
wreck. How he did it I cannot tell, but of this I am sure, that most
probably radium helped him by making luminous and visible the
instruments which guided him.
But probably it has rendered and will still render us even greater
services in the way of helping to repair the damages to our injured
manhood. How many men came back from the war crippled with rheumatism
because of the hardships through which they went. That disease is
believed to be due to a substance which mingles with the blood and
which, although usually liquid and harmless sometimes changes into a
solid and settles in the joints. Now it is believed that radium properly
administered will act upon that solid and cause it to change back into
its liquid form again, thereby curing the disease. Certainly many of the
mineral springs at such places as Bath and Buxton give forth a water
which shows a certain amount of radio-activity and it may be that which
gives those waters their healing properties. If so, we may look forward
with confidence to the time when radio-activity will be induced to play
a still more successful part in meeting this painful and widespread
illness.
Then, of the other ills which will inevitably arise in our men through
the hardships which they have endured are sure to be some of the
cancerous type, many of which appear to succumb to treatment by radium.
If a very small quantity indeed be carried for a few days in a pocket it
will imprint itself upon the skin beneath as if it burnt the tissues. It
is never advisable, therefore, to carry radium in the pocket without
special precautions. One cannot help feeling, however, that in that
little fact is a hint of usefulness when the best modes of application
have been discovered, for as a means of safely and painlessly burning
away some undesirable growth it would seem to be without a rival. It is
said, too, that it has the strange power of discriminating between the
normal and the abnormal, attacking the latter but leaving the former, so
that when applied, say, to some abnormal growth like cancer it may be
able to remove it without harmful effect upon the surrounding tissues.
Of this, however, it is too soon to write with confidence. It has not
been known long enough for our doctors to find out the best modes of
use, but that will come with time: meanwhile there are indications that
in all probability it will render good service to mankind.