50 l^he Philippine Journal of Science isis 



to the above unit gives a value of 2.3. This method, however, 

 is open to objection, and the result obtained is rather uncertain, 

 although valuable as showing the order of magnitude of the 

 quantity to be determined. 



Eve," in 1907, made a determination of the radium content 

 of Ignau sea salt and also of a sample of sea water from the 

 middle Atlantic and obtained values of 0.3 and 0.6, respectively. 



The first extensive series of determinations on sea water was 

 made by Joly * in 1908. His method is described as similar 

 to that used by Strutt with the exception that he boiled his 

 sample under a partial vacuum and finally filled with distilled 

 water in order to drive over all the gas containing emanation 

 into his collecting chamber. In the course of his determinations 

 he found that in order to liberate all the emanation generated 

 in the sample within a given time it was necessary to acidify 

 with hydrochloric acid. Especially was this the case with cer- 

 tain samples. This is probably due to the fact that during con- 

 centration any precipitates of barium or of sulphates that 

 may form will tend to carry down with them some of the radium 

 and that the emanation is liberated therefrom with difficulty. 

 He also found that his first determination on a given sample 

 generally gave a value considerably lower than subsequent tests. 

 Consequently in making up his mean for any given sample his 

 first determination was omitted. In a later paper = Joly gives 

 the results for twenty-five samples from the north Atlantic 

 and Indian Oceans. His highest values were obtained for sam- 

 ples collected off the coast of Ireland, the mean value for five 

 different samples being 34. His lowest value was 2.2 for a 

 sample from the Mediterranean. His mean value for the twenty- 

 five samples is given as 16. 



Eve," in 1909, published the results for determinations on six 

 samples of sea water collected at different points in the north 

 Atlantic between Liverpool and Montreal and obtained a value 

 of 0.9 as the mean radium content, the maximum range being 

 from 0.5 to 1.5. 



Satterly ' made several determinations on sea water from 



' The ionization of the atmosphere over the ocean, Phil. Mag. (1907), 13, 

 248-258. 



'The radioactivity of sea-water, ibid. (1908), 15, 385-393. 



•On the radium content of sea-water, ibid. (1909), 18, 396-407. 



'On the amount of radium present in sea-water, ibid. (1909), 18, 

 102-107. 



' On the radium content of various fresh and sea-waters and some other 

 substances, Proc. Cam. Phil. Soc. (1912), 16, 360-364. 



