BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 31, pp. 419-424 November 30, 1920 



CHEMICAL EESEARCHES ON SEDIMENTS ^ 



BY iiKHBHrn: 1:. mkrwin 



{Read before ike SocicliJ Decemher 31, Wli)) 



CONTENTS 



CJeiieral considerations 419 



Some illustrative problems 421 



Dolomite 421 



Oceanic red claj-^ 422 



The primary rock phosphates 422 



OeNERAL COXSIDEIJATIONS 



The clieniical i)r()l)lem8 growing out of studies of sedimentary rocks 

 must, even more than other problems, be viewed from many angles. 

 Each such problem is likely to lead to several highly specialized studies 

 in restricted chemical fields. The mere statement of any one of these 

 special problems will often require an extended study of its general chem- 

 ical, geological, and biological setting. Because of the special nature of 

 these chemical problems, no general outline for their study needs presen- 

 tation here, but it may be worth while to present some viewpoints from 

 which the problems may be seen. 



From the standpoint of physical chemistry many of the problems of 

 sedimentar}^ rocks are especially dii^cult, because the solutions concerned 

 may be very dilute and very complex; the solid phases are often ill-de- 

 fined physically, or are stable at temperatures so little above the ordinary 

 that heat to speed up reactions can not be effectively applied ; or unstable 

 fomis may appear and persist indefinitely. 



An important chemical consideration respecting the consolidation or 

 recTvstallization of sedimentary rocks is the effect of differential stress. 

 Adjacent grains arc partially separated by films of liquid. These films 

 are so thin in places tliat tlioy arc able to transmit stresses from grain to 



' Manuscript received by the Secretary of the Society March 3, 1920. 

 This paper is one of a series composing a symposium on sedimentation. 



(419) 



