270 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



probably keep bark certain forms, and the steady ri 

 throughout April may influence these organisms. 



SC 



Oxygen Determinations. 

 In these first oxygen observations for the Irish Sea, the 

 method employed was that of von Winkler, which was 

 used by batterer in his work on the " Pola " expedition. 

 A number of bottles with well fitting glass stoppers, 

 and holding about 275 c.c., had the volume accurately 

 determined by weighing bottle and stopper, at first dry 

 and then filled with distilled water, the stopper being 

 placed in so that no air bubbles were by any chance 

 included. The glass stoppers must have no hollows under- 

 neath where air bubbles might possibly collect. The water 

 was collected as for salinity samples by the Ekman 

 Reversing Water-bottle, but a piece of indiarubber tubing 

 was fixed to the tap on the bottle and the end let down to 

 the bottom of the glass bottle, so that the water ran in 

 when the tap was opened without splashing or enclosing 

 air bubbles. The procedure on the yacht was as follows : 

 A bottle was completely filled with the sea- water to be 

 examined. By means of pipettes with long narrow stems, 

 first 2 c.c. of concentrated solution of NaHO (36 gr. pure 

 caustic soda in 100 c.c. of distilled H 2 0, to which 10 gr. 

 of potassium iodide are added) and then 1 c.c. of 

 manganous chloride solution (40 gr. MnCl 2 4H„0 in 

 100 c.c. dist. water) were introduced carefully, so that 

 they remained at the bottom of the bottle. The stopper 

 was then inserted, causing some sea-water to overflow, 

 and the bottle well shaken and brought back to shore for 

 further treatment in the laboratory. The precipitate was 

 allowed to settle and then 2 c.c. or more fuming hydro- 

 chloric acid were added, which dissolved it, the reaction 

 setting free a quantity of iodine, equivalent to the oxygen 



