CONTAINED IN THE AIR ABOVE THE IRISH SEA. 157 



about twenty-eight of oxalic acid ; but of course the exact 

 strength of the baryta- water was ascertained previously to 

 each experiment. 



The bottles were generally fiUed with the air by means 

 of bellows ; but sometimes, when the wind was strong, it 

 sufficed to hold them up. for a minute or two in such a 

 manner that the air could circulate freely within. The 

 baryta- water remained in contact with the enclosed air for 

 three-quarters of an hour to one hour, during which time 

 the bottles were frequently agitated. Although even this 

 is longer perhaps than is actually required for the complete 

 absorption of the carbonic acid, still, for the sake of con- 

 clusiveness, in experiment 4 the bottles were allowed to 

 stand for three hours, and in experiment 13 for six hours, 

 before the solutions were tested. The capacities of the 

 two bottles which served for all the experiments were 4815 

 c.cm. and 4960 c.cm. The burette was Mohr's modification, 

 for which a table of calibration had been constructed by 

 weighing and interpolating in the ordinary way. 



As an example of the process and mode of calculation, 

 take the experiment where the baryta^ water remained in 

 contact with the air for six hours : — 



Aug. 17th; time, sunrise; bar. 753* i millims. Tempera- 

 ture : dry bulb I3°.9 C, wet bulb I2°.8 C. ; wind W.S.W., 

 fresh. Cloudy, amount of cloud (overcast =10) 9 ; nature 

 of cloud, cirrostratus. Temperature of sea-water, i5°.o C. 



50 c.cm. of baryta- water before experiment were equal to 

 55* 18 c.cm. oxalic acid. After the expiration of the six 

 hours, 25 c.cm. of the baryta-water required 26'29 of oxalic 

 acid solution for neutralization ; therefore the 50 c.cm. ori- 

 ginally taken would require double this quantity, namely 

 52*58 c.cm.; and 55*i8— 52'58 = 2-6o. But as one cubic 

 centimetre of oxalic acid solution is made equal to one milli- 

 gramme of carbonic acid, this number corresponds to 2'6 

 milligrammes of carbonic acid in the amount of air taken 



