THE COMPOSITION OF WOODS HOLE SEA WATER. 



IRVINE H. PAGE. 1 



There are no more fundamental quantitative data than those 

 regarding the composition of the medium nurturing the organisms 

 on which much of the study of biological laboratories is based. 

 Analyses of the tank water in the Marine Biological Laboratory 

 were therefore made using the methods briefly outlined below. 



Calcium and Magnesium. 50 cc. samples of sea water were 

 boiled with a little HC1 to expel CO 2 , cooled and the calcium 

 precipitated as oxalate, the oxalate subsequently ignited and 

 weighed as CaO. Magnesium was precipitated in the nitrate 

 with Na 2 HPO 4 in the presence of an excess NH 4 OH, ignited and 

 weighed as the pyrophosphate. 



Potassium was determined in i cc. samples of water by the 

 method of Kramer and Tisdall (i). This method essentially 

 consists in the precipitation of potassium with cobalti-nitrite 

 reagent, and titration of the precipitate after special washing with 

 KMnO4. The method has been found to be exceedingly accurate 

 and therefore has many advantages over the old, classical and 

 tedious, precipitation as the chloroplatinate or the perchlorate. 



Sodium was estimated by a modified Kramer and Gittleman 

 technique (2). W T e have found that modification of the original 

 technique which was designed for blood serum only and for this 

 most useful is necessary because both calcium and magnesium 

 are precipitated practically quantitatively by the sodium reagent, 

 and are titrated along with the sodium. 



The modified method consists in preliminary precipitation of 

 the calcium and magnesium with alkaline phosphate, centrifuging 

 off the precipitate, concentrating the supernatant liquor to about 

 3 cc. on the water bath, cooling and adding 10 cc. of the alkaline 

 potassium pyroantimonate reagent, then 3 cc. of redistilled (over 

 KOH) ethyl alcohol drop by drop with vigorous shaking. This 

 precipitation is carried out in 50 cc. conical bottom Pyrex 

 centrifuge tubes; it is important that these be used. After one 

 half hour standing the tubes are centrifuged and the procedure 

 carried out as Kramer and Gittleman recommend. 



1 Contribution from the Research Division of Eli Li'ly and Company, Marine 

 Biological Laboratory, Woods Hole, Mass. 



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