immersed in water was —0.006°/oo, whereas in all cases for those samples 

 out of water the observed increase of salinity was considerably less 

 than calculated, averaging 0.038°/oo less. Cox similarly computed 

 the salinity that a sea water sample might have if it lost weight at the 

 rate that his distilled water did and concluded that a sample of sea 

 water at 35.000%o could easily increase 0.100°/oo in a month. To 

 the contrp.ry, we found an almost negligible change in salinity at the 

 end of 1 month and a maximum increase of only 0.038°/oo at the end 

 of 8 months. 



Summary and Conclusions. Six polyethylene bottles filled with sea 

 water were stored under field conditions for periods up to 8 months. 

 There was an overall increase of salinity after the first 2 months of 

 storage. All bottles lost weight; the last two of these bottles, one at 

 6 months and one at 8 months, lost 1.23% and 2.07%, respectively, 

 of their weights, in close agreement with the 1.5% weight loss at the 

 end of 8 months found by Romanovsky. 



Three more bottles were placed in a relatively airtight container; 

 prior to each salinity determination the bottle exterior was washed and 

 this wash water was analyzed to determine if salt solution or only water 

 was passing through the polyethylene walls. A flame photometer 

 showed that there was no appreciable change in salt content over the 

 entire period, although the photometer may have been operating at its 

 lower level of sensitivity. The third and final bottle exhibited an 

 anonialous behavior by a large increase of weight with its salinity 

 increase. 



Six bottles with sea water inside were immersed in tap water inside 

 a covered container. There was generally a gain of weight and a 

 decrease of salinity, which indicates a transfer of water into the bottle. 

 This also stresses the effect of humidity upon the bottle contents, as 

 pointed out by Cox. 



It is apparent from the foregoing that there is some change of 

 salinity associated with a change of weight within a polyethylene 

 bottle, but its magnitude is only about 1/1 00th that of the change in 

 weight. This is much less a salinity change than was computed by Cox, 

 but is more than the negligible change observed by Romanovsky. 



It is concluded, therefore, that polyethylene bottles can be used to 

 store samples of sea water for periods up to several months without an 

 appreciable change in salinity. Furthermore, it is believed that the 

 salinity uncertainty of the samples from the Evergreen postseason 

 cruise stored for 2 months in late summer 1962 is less than the proposed 

 uncertainty of 0.04°/oo mentioned in Bulletin No. 48 of this series. 



REFERENCES 



Cox, ROLAXD A. 



1954. Water transmission of polyethylene bottles. J. Cons. 

 Int. Expl. Mer 19: 297-300. 



77 



