JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. io MAY 4, 1920 No. 9 



GEOCHEMISTRY. — -An unusual deposit of aragoniie from sea- 

 water. Roger C. WeIvLS,^ U. S. Geological Survey. 



A few months ago the writer had occasion to examine for the 

 United States Bureau of Fisheries some samples of standard 

 sea-water contained in sealed glass tubes as originally furnished 

 by the Copenhagen Laboratory of the Conseil Permanent Inter- 

 national de la Mer. The tubes bore the date April 15, 1913, and 

 had remained at rest, awaiting use, for most of the intervening 

 interval. A slight deposit had formed on the inside of several 

 of the tubes, apparently around air bubbles, but nevertheless 

 insoluble in the water after long agitation. As it was feared that 

 the chloride content of the water had changed, very careful deter- 

 minations were carried out by the gravimetric method, which 

 showed that the chloride content marked on the tubes was sub- 

 stantially correct, the value 19.386 being found, whereas the 

 value on the labels was 19379 parts of chlorine per 1,000 parts of 

 sea-water. 



Attention was next directed to the crystals. A few simple 

 tests showed them to be calcium carbonate. They had a pris- 

 matic or needle-like appearance and were arranged in stellate 

 groups. Some of them were a few tenths of a millimeter in length. 

 Dr. E. S. Larsen of the Geological Survey very kindly determined 

 their indices of refraction as follows : 



a = 1.525 =fc 0.003 

 /3 and 7 = 1.675 =*= 0.003 



The crystals are therefore aragonite, and represent a deposit 

 under apparently very definite conditions. Some of the crystals 



* Published by permission of the Director, United States Geological Survey, 

 Received March 26, 1920. 



