STABILIZATION OF PHOSPHATE IN SEA WATER 



73 



on the following day, the last on the forty-fifth 

 day. The results are shown in table 2. 



While only small differences developed between 

 the means of the initial and the final sets, five 

 means were different, according to the t test. 

 These variations between time intervals, while 

 slight, are reflected in an F value of 3.78, which 

 is significant at the 1 -percent level. 



From the results of these first two experiments 

 it became suspect that the 2-hour interval re- 

 quired to draw and freeze the 10 sets introduced 

 a variable, in that changes in inorganic-phospho- 

 rus content were taking place even in that short 

 interval. Subsequent experiments were designed 

 to control this variable. 



Table 2. — Changes in inorganic-phosphorus concentration 

 of sea water occurring at subzero temperatures 



A. VALUES IN (1-ORAM ATOMS Or POl-P PER LITER 



B. COMPARISON O? MEAN OF INITIAL SET WITH MEANS Or 

 SUBSEQUENT SETS 



Time interval 



1 day.. 



2 days. 



3 days. 

 6 days. 

 8 days. 

 21 days 

 29 days 

 37 days 

 46 days 



Difference 



between 



means 



-0.33 

 -.10 

 -.13 

 -.21 

 -.17 

 -.15 

 -.16 

 -.03 

 -.06 



Value of ( 



•5. 072 

 2.301 

 1.677 

 •3. 179 

 •2. 847 

 •2.667 

 •3.868 

 .509 

 1.046 



Degrees of 

 freedom 



Experiment 3 



Experiment 3 was designed, as were experiments 

 1 and 2, to measure the differences between rates 

 of change in inorganic phosphorus stored at room 



temperature and at subzero temperatures. It was 

 modified from these by the addition of inorganic 

 and organic phosphorus, the former as potassium 

 phosphate (dihydrogen) C P., the latter as sodium 

 glycerophosphate (Eastman). These were added 

 to ensure a sufficient substrate of phosphorus to 

 permit greater changes in concentration than 

 could occur in phosphorus-deficient natural sea 

 water. 



The sea water for this experiment was taken 

 from Galveston Beach. After adding the phos- 

 phorus, the mixture was filtered before drawing 

 the samples. Altogether, 13 sets of samples were 

 drawn, 5 to be kept at room temperature, 8 to 

 be frozen. The results of these experiments are 

 shown in tables 3 and 4. 



In the 25 days during which the samples were 

 held at room temperature, the concentration of 

 inorganic phosphorus nearly doubled (table 3). 

 As shown by the I test, each set of samples was 

 significantly different from the initial set. The 

 high values for the mean squares in the analysis 

 of variance indicate the great differences which 

 resulted between sets as compared with the differ- 

 ences within sets. 



Table 3. — Changes in inorganic- phosphorus concentration 

 of sea water with added phosphorus, occurring at room 

 temperature 



A. VALUES IN fl-OBAM ATOMS Or PO.-P FEB UTEB 



Time interval 



Initial. 

 1 day.. 

 3 days . 

 17 days 

 25 days 



Number 

 inset 



Mean 



5.83 

 6.38 

 8.01 

 8.90 

 10.24 



Standard 



deviation 



0. 1202 

 .148 

 .357 

 .226 

 .232 



Fiducial 

 limits (f..i> 



0.134 

 .152 

 .367 

 .232 



.238 



