REDISTRIBUTION OF SODIUM. 997 



Sodium is a constituent of many of the minerals of the original 

 igneous rocks. These minerals comprise the feldspars, the nephelites, 

 cancrinite, sodalite, haiiynite, noselite, and marialite. In the meteorites 

 sodium is reported only in the feldspars. Because of the dominating 

 importance of the feldspars" the larger part of the sodium occurs in them, 

 although the sodalite and nephelite groups of minerals are important 

 sources of the element. Sodium is so abundant in the acid plagioclases as 

 to give them the name of soda feldspars. 



In 78 shales soda composes 1.31 per cent; in 624 sandstones, 0.61 per 

 cent, and in 843 limestones, 0.34 per cent. It thus appears that in the 

 shales the amount of soda is reduced to only about one-third of that in 

 the original rocks, in the sandstones to about one-sixth, in 345 limestones 

 not used for building purposes'" to a minute fraction, but in 498 lime- 

 stones used for building purposes to about one-sixth. (See p. 938.) 



Multiplying the percentages of soda in each of the classes of sediments 

 by their masses and taking- their sums we have the average percentage of 

 soda in the sediments, thus: 



1.31X.65+.61X.30+.34X-05=1.0515. 



Since the soda in the original rocks is 3.55 per cent, the deficiency in the 

 sediments is 2.4985 per cent. It thus appears that the deficiency in the 

 sediments considered is about 70.38 per cent of the total amount of soda in 

 the original rocks. For the entire weight of the sediments this gives a 

 deficiency of 475,065,000,000,000,000 metric tons. 



It is possible that when more analyses have been made of sedi- 

 mentary rocks the estimates of soda in them may be somewhat increased, 

 but since the analyses show the amount of potassium to accord fairly well 

 with that of the original rocks (see p. 1000), it does not seem probable that 

 much of the deficiency in soda can be explained by insufficient analyses. 



The natural source to which one immediately turns to account for this 

 vast deficiency is the ocean. The actual amount of sodium in the ocean, as 

 determined from Dittmar's estimates, is 14,180,000,000,000,000 metric tons, 

 which, reckoned as an oxide, would be 19,101,000,000,000,000 metric tons. 

 While sodium is the most abundant element in the ocean with the exception 

 of chlorine, and is more than five times as abundant as the magnesium. 

 «Clarke, cit., Bull. 168, p. 16. ^Clarke, cit., Bull. 168, pp. 16-17. 



