USE OF RADIOACTIVE SUBSTANCES AS FERTILIZERS. 3 



PROPERTIES OF THE RADIO-ELEMENTS. 



The properties of the radio-elements have been investigated by 

 many of the leading scientists of the present day and have conse- 

 quently been determined with a degree of exactness and completeness 

 which perhaps has never before been equaled in any other branch 

 of science in the same length of time. 



The following points with regard to these properties may be 

 enumerated as having bearing on the fertilizing value of radioactive 

 material : 



1. An element is said to be radioactive when it has the property 

 of disintegrating or changing into another element. This property 

 of radioactivity as exhibited by radium, which is the best known 

 popularly of the radio-elements, is one which is inherent in the atom. 

 No substance can be radioactive which does not contain an element 

 which would be radioactive if separated from the substance, and, 

 conversely, if a substance contains such an element, it must be radio- 

 active. Some of the radio-elements, like the ordinary elements, do not 

 give off any rays; others give off one kind of rays only; while still 

 others give off two different rays, each of which may differ from the 

 single radiation, thus making altogether three different kinds of rays. 

 No inactive substance can be made radioactive by exposure to any of 

 these rays. The activity of a given quantity of a radioactive element, 

 like uranium or radium, remains unchanged in whatever chemical or 

 physical state it may exist, whether combined in a soluble or insolu- 

 ble compound, and whether or not it may be mixed with any sub- 

 stance or substances whatsoever. It therefore follows that its activity 

 can not be intensified by mixing with barnyard manure, as is some- 

 times claimed. 



2. Radium is a product of uranium and can not occur in* nature in 

 quantity exceeding the amount with which it is in equilibrium with 

 uranium. For this reason the highest concentration of radium which 

 can ever be found in any ore will amount to only one part of radium 

 in 3,460,000 parts of ore. This quantity of radium is so small that 

 if chemical tests alone had been applied neither radium nor any of 

 its products could ever have been identified. There are physical 

 tests, however, which are much more delicate than any chemical tests. 

 Thus, when the spectroscopic test is applied to lithium, an element 

 which according to chemical tests is of very limited distribution, it 

 is found to be almost universally distributed, and in no spring water, 

 for example, dees the test fail to reveal its presence. The electro- 

 scopic test for radium is even much more delicate than the spectro- 

 scopic test just cited, and it thus happens that radium which occurs 

 in soils, for example, in such minute quantities can nevertheless be 

 identified in all soils. If the same delicate test could be applied to 

 all the ordinary elements, it is universally admitted that they, too, 



