| Show RADIUM AND OTHER radioactive substances by louis A pearsons Pea sons ph P D instructor int in physics university of 0 y eteh the new element radium has attracted worldwide world wide attention not only among scientific people but among the general reading public the newspapers we have seen have told us this and that about radium always something wonderful we have been told that it Is an enormously valuable metal and also that there are large quantities of it in our own state the prodigious amount of energy that it gives off spontaneously is always emphasized and we have been told that here we have a continuous creation of energy a distinct violation of the principle of the conservation of energy and that as a consequence a large part of the foundation of modern physics will have to be reconstructed such a statement is decidedly wrong there is no violation of the conservation of energy and rather than disproving our modern theories the new facts brought out by a study of radium have strengthened and advanced them in view of what we have already learned the claims we hear in the newspapers of some inventor not before heard of in the field of science perfecting a means of using the energy in a little vest pocket tube of radium to run a threshing machine or something of the kind is simply absurd yet there is enough that is true about radium that is very wonderful indeed light as we all know travels trave is in straight lines and most of us have been told that it consists of a series of waves in the ether when we sit in front of a red hot stove and put something in front of our faces to keep the heat away we show that we know that heat travels out from the stove in straight lines which carries energy along with it a radiation both light radiation and heat beat radiation consist of waves in the ether wireless telegraphy makes use of another radiation another set of either waves the electric waves the X rays ate are another type of radiation and consist according to J J thompson and stokes of disconnected sharp pulses in the ether they pass through substances opaque to ordinary light and cannot be either regularly reflected refracted or polarized the cathode rays which are given off from the cathode in a highly exhausted vacuum tube as an xray X ray tube form another type of radiation fadia tion they travel in straight lines and carry rry energy they have been shown by J J thomson to consist of streams of negatively electrified particles corpuscles corpus cles or electrons moving with a velocity of miles iles a second or more under the bombardment bar bar dment of these particles substances giving off different colored light orld and also 0 o at each sudden stoppage of a corpuscle an xray X ray pulse is sent off through the ether the cathode rays are deflected by magnets the cathode rays or the X rays or electric waves require a continuous supply of electric energy and cease as soon as the supply stops in fact all radiation requires a continuous supply of energy there have been found however certain F substances which spontaneously give off radiations analogous to the cathode rays and to the X rays without any obvious supply of energy these radiating substances are called radioactive substances and radium is one of these the first body found to be radioactive was the metal uranium H Becque rel who made this discovery in france says that it followed as a consequence from the ideas arising from the discovery of the X rays he was trying to find if there was any connection between florescence such as is produced by the X rays on certain substances and the action on a photographic plate and placed various fluorescing or phosphorescing bodies over photographic plates wrapped in black paper he placed a coin on one and over the coin some double sulphate of uranium and potassium after exposing it a day or more he obtained on development a clear image of the coin with a distinct outline of the head on it 1 and some of the details as the ear this was in february 1896 rapports Rap ports congles international de physique paris 1900 vol III he soon found that this action was independent of the fluorescence and resulted whenever metallic uranium or any of its compounds were used the radiation which Becque rel thus discovered was called Becque rel rays he found that these rays discharge electrified bodies and that they ionize gases through which they pass i e render them electrically conducting rutherford of mcgill university montreal soon showed that these rays or part of them can be deflected by a magnet or by an electrostatic tro static field just as the cathode rays soon after the discovery of these uranium rays investigators began in the examination of other metals and minerals for radioactivity in 1898 schmidt found that thorium and its compounds possess a r radioactivity of the same order as that of uranium about the same time M and mine curie in paris made a systematic examination of all the ordinary metals and non metals of the rare elements gallium germanium praseodymium niobium scandium gadolinium gadolini tim erbium samar juanf ium rubidium detri yttrium um yeter ytterbium ye terbium blum and hol and a great number of rocks and minerals rapports Rap ports congles international de physique paris 1900 vol ill III they discovered early in 1898 independently of schmidt that thorium and its compounds are radioactive they found a large number of minerals containing uranium and thorium to be radioactive such as pitchblende char colite the rite org anite monazite mon ozite xeno tyme aes chynita chy nite and they found what was most remarkable that the containing oride of uranium in the crude mineral state possessed an activity four times that of pure metallic uranium and phosphate pros phate of copper and uranium an activity twi twice ce that of pure uranium the only possible explanation was that these minerals contained some other material many times as radioactive as uranium in the chemical separation the radioactive material remained closely associated with barium As barium had previously been found not radioactive they believed it was ivas some substance associated with the barium they succeeded in separating two distinct radioactive substances or at least to effect a separation complete enough to enable them to be studied and identified as new elements one they succeeded in completely isolating and c found its radioactivity to be times that of uranium or thorium they gave to it the name of radium the other one they called polonium in the chemical separations it remained associated with bismuth tn in the following year 1899 a third element actinium was discovered by Deb De bierne lerne it ic tc companies metals of the iron group and is found in thorium minerals radium polonium it and acter actinium ilum have about the same order of radioactivity the conclusions of the curies auries that radium is a new element was substantiated soon after by the discovery of its spectrum by demarcay in 1902 mme ame curie by a fractional crystallization of a large quantity af f barium chloride obtained 1 10 grain I 1 rain of radium chloride quite pure and arom rom this determined as a mean of three determinations the atomic weight of radium to be by its chemical properties radium belongs to the alkaline earth series and in the periodic system lies between barium and thorium and uranium all bodies if heated will radiate heat ind some substances if exposed to the light will in the dark radiate light but the radiation in all these cases gradually dies down and then ceases light heat electric waves cathode rays and X rays all require a continuous supply of energy to be kept constant but radium or any of these other elements continuously and spontaneously radiates adi ates energy at a constant rate radiations of light and h heat eat depend upon tem grature lera era ture and vary greatly with varying tem bra brasure era ture but the radiation of radium remains mains con constant stant through the enormous ange of temperature f from rom a red heat to that of liquid air all heated bodies i 0 if left to themselves and free to radiate energy soon come to the same temperature as that of the surrounding air but curie and labarde found that the temperature of radium is always 5 degrees to 6 degrees fahrenheit above that of surrounding bodies these remarkable facts can be explained only on the assumption that radium possesses within itself a continuous supply of energy this however does not mean a creation of energy it has been shown that chemical changes are continually going on in the substance and this change is the source of the energy the change being into a form possessing less energy radiation from these radioactive elements readily passes through black paper thin metals and other substances opaque to ordinary light but some of the rays are much more penetrating than others they cause certain minerals and chemical compounds to fluoresce all of the radium compounds are spontaneously luminous but the dry hallid salts emit a particularly intense light which may be seen in a partially dar darkened keneI room the raye ionize gases and prepuce chemical changes they produce an intense violet or brown coloration in glass paper and hallid salts of metals are discolored ozone is produced in the air near the radiation radium bromide dissolved in water produces electrolysis of the water and helium is also obtained as a product giesel confirmed earlier observations in regard to skin wounds due to these rays by applying gram of radium barium bromide in a capsule to the arm in two or three weeks after much inflammation the skin peeled off the physiological effects are analogous to those of the X rays and it seems fair to assume that they may be used in all medicinal work in which X rays are used as in the treatment of cancer tubercular growths and lupus and other skin diseases if radium could be obtained in quantities it would furnish a continuous source of energy for these purposes with out the use of expensive tubes coils and electric current As has been pointed out the radioactivity of these substances is independent of external sources of energy and hence originates in the substances themselves since the radioactivity of any substance is found to be the same no matter what the condition of the surface or whether the substance is in large masses or is powdered or in what physical condition it is it cannot be a property of the mass as a whole but must be a property of the molecular or atomic structure since the radioactivity of each of the elements is of a type peculiar to itself but occurs the same in all substances whose molecules contain atoms of this element and since moreover the radioactivity is independent of all changes of temperature which have such marked influence on all chemical reactions molecular changes the phenomenon must b bg atomic or subatomic sub atomic in nature As we pursue the subject further in the light of ruth fords edfords er researches we are led to the conclusion that the atoms themselves are complex and that radioactivity arises from the energy of the system within the atom rutherford has carried on the most extensive study of the radiations from these substances substance s par particularly ticul arly thorium he found that the radiation is complex consisting of three distinct types 1 the alpha rays 2 the beta rays and 3 the gamma rays the gamma rays are extremely penetrating passing through iron a foot thick and not being affected in the least by magnetic or electric fields they are analogous to the X rays they are not easily observed the beta rays are the ones which have been most generally studied the ones which produce most of the photographic action they are very penetrating though not nearly so much as the gamma rays and are easily deflected by magnets and electrified plates and hence are called the rays they have been shown to consist of streams of negatively electrified particles moving with a velocity of about miles a second nearly as great as the velocity of light and having masses about 1000 1 the mass of an hydrogen atom they are in all respects analogous to the cathode rays excepting that they move faster the alpha rays have very low penetrating power being entirely absorbed by a thin sheet of paper or a thin layer of air and hence are ordinarily observed only near the surface of the radioactive body they seem however to be the most important of all as regards the radioactivity of the substance they are not affected to any appreciable extent by magnetic and electric fields of ordinary strength it was thought that they were not affected at all and hence received the name of the non rays rutherford however found that they are deflected by strong fields and showed that they consist of streams of positively electrified particles having a velocity of perhaps 1 10 that of the beta rays and having masses about twice that of the hydrogen atoms rutherford showed that in the radioactive substances there is a chemical change going on all the time producing another chemical substance having evidently less energy than the original substance and hence energy is liberated during the change and this is doubtless the source of the energy of the radiations in the case of thorium he succeeded in chemically separating this new substance formed from the thorium itself and called it thorium X just after sepe ration the thorium was only slightly radioactive while the th X was many times more intensely radioactive than the original thorium the radiation from the th X consisted only of the beta rays while the alpha rays were associated with the ti th the th X kept by itself gradually lost its radioactivity while the thorium at the sam aag rate regained its original ginal due to the production of freseth fresh th X these two processes if the th X were not separated from the thorium would maintain the radioactivity constant as it had been observed to be Becque rel had observed a similar substance produced by the disintegration te of uranium which he called uranium X no similar substance has been found for radium rutherford discovered another product of the disintegration of thorium which is spontaneously thrown off from the th thorium orlum but is not a radiation for it does not travel in straight lines is entirely cut off by the thinnest layer of mica but passes through plugs of cotton wool can be blown aside by a current of air and conducted through glass tubes in short it acts in all respects like a gas to it he gave the name of thorium emanation radium also has an emanation but none has been found for uranium these emanations have been separated and stored in vessels and have been found to be gases about times as heavy as hydrogen the thorium emanation according to rutherford can be condensed to a liquid at degrees C and the radium emanation at degrees C the amount of energy stored in the emanation is enormous if a cubic centimeter could be collected the bombardment due to the powerful radiations would heat to a red heat if it would not melt down the walls of the glass tube containing it the emanation is itself radioactive sending off radiations it also has the property of rendering all bodies upon which it falls temporarily radioactive or of pro producing on their surfaces an induced radioactivity which is itself according to rutherford another distinct chemical substance a disintegration product the emanation itself spontaneously disintegrates into another substance the final form of which is not radioactive an experiment of ramsey suggests that the gas helium is a disintegration product of the emanation of radium all these changes and the attendant radiations diat ions are due rutherford believes to disintegrations of the atoms themselves all the radioactive elements have very great atomic weights and we would expect very complex atoms we must think of each atom as having within itself a large number of electrons |
