Quantity of Radium in Rocks and Minerals, Sfc. 135 



The causes which retain emanation in certain solutions 

 ^appear to be obscure. Rock solutions may occasionally yield 

 diminished, occasionally increased, amounts of emanation on 

 successive experiments. These cases seem to be exceptional. 

 There is some reason to believe that, additional to that part 

 of the emanation which is soluble in the boiling solution, 

 emanation may be retained from some other cause or causes. 

 This has been referred to as explained by adsorption. This 

 explanation may apply to the case of perfectly limpid solu- 

 tions containing radium, and from which only a fractional 

 part of the emanation is removable by ebullition. An inter- 

 esting case of this kind, which occurred in my laboratory, is 

 referred to by Fletcher (Phil. Mag. June 1911, p. 770). A 

 well-known similar case is recorded by Rutherford and 

 Boltwood. It is probable that the deficient return of emana- 

 tion observed when known amounts of radium are added to 

 rock solutions, is due to other causes, for in this case there 

 is no want of acidification. I here refer to the fact that a cali- 

 bration constant obtained by boiling off the emanation from 

 •an acid solution of a rock to which a known quantity of 

 radium has been added, is higher than if a like quantity 

 of radium is treated in an acid, but otherwise pure aqueous 

 solution. The quantities boiled off in the two cases may be 

 about in the ratio of 6 to 8. 



In addition to the foregoing objection the risk of contami- 

 nation during the lengthy manipulation required in the pre- 

 paration of the solutions is considerable. The very great 

 labour involved in effecting the preliminary solution, and the 

 final delay attending the regeneration of the emanation in 

 the solutions are, perhaps, minor objections ; but still they 

 are serious in so far that where very many results are desirable 

 the observer is often forced to bo contented with an insufficient 

 number. 



For these reasons I have from time to time sought for some 

 means of collecting from the rock the emanation originally 

 prevailing in it, and with a minimum of manipulation and loss 

 of time. Some years ago I found that the emanation con Id 

 be collected from a rock while this was undero-oino- fusion 

 and decomposition along with alkaline carbonates. Very 

 encouraging results were obtained. In these experiments 

 the powdered rock was mixed with 3 or 4 times its weight 

 of the mixed carbonates of sodium and potassium, and 

 enclosed in a platinum retort. The nozzle of the retort 

 being kept cool by a water jacket, a rubber connexion could 

 be attached to it, serving to convey the issuing gases to 

 absorption-tubes containing soda-lime, and finally to a gas- 



