On the Absorption of Carbonic Acid. 483 



" On the Absorption of Carbonic Acid by Saline Solutions." 

 By J. Y. BUCHANAN, Chemist on board H.M.S. ' Challenger.' 

 Communicated by Professor A.W.WILLIAMSON, For. Sec. B/.S. 

 Received December 11, 1873*. 



In the examination of sea-water, whether it be regarded from a chemical 

 or from a zoological point of view, the determination of and the varia- 

 tions in the amount of carbonic acid in different parts of ocean must 

 always be an object of importance. This is more especially so when a 

 parallel series of observations on the quantity of oxygen present is 

 carried out. At the surface we should expect to find the quantities of 

 these gases following the law of partial pressures ; at greater depths, 

 however, where the water for long periods only comes in contact with 

 water, we should expect to find the quantity of oxygen decreasing and 

 that of carbonic acid increasing with the amount of animal life. The in- 

 vestigation from this point of view of the bottom-water, at greater and 

 smaller depths, presents perhaps a more interesting field of observation 

 than that of intermediate depths. Down to nearly 2000 fathoms life is 

 still abundant ; below this depth, however, the amount rapidly decreases 

 till, at about 2800 fathoms, it is, for carbonic-acid producing purposes, 

 practically extinct. "We have, then, to settle the variation of the car- 

 bonic acid with latitude and longitude, with depth, with nature of bottom, 

 and with nature of atmosphere. 



In order to solve these problems, it is before all necessary to have a 

 reliable method for the determination of the carbonic acid. For the 

 discovery of a cause of error in the old method, and for the invention 

 of a new one, we are indebted to Dr. Jacobsen, of Kiel. Dr. Jacobsen 

 found that sea-water could not, as had been till then assumed, be 

 thoroughly freed from its dissolved carbonic acid by merely boiling in 

 vacuo't. He found that it was necessary to boil clown almost to dryness 

 before the last traces of carbonic acid could be expelled. Being parti- 

 cularly interested in the matter, I immediately commenced a series of 

 experiments to determine, if possible, the salt or salts to which sea-water 

 owes this peculiar property. A short resume of the results of these ex- 

 periments have been published as an appendix to Professor Wyville 

 Thomson's ' Depths of the Sea.' 



I purpose here to give a detailed account of the experiments performed. 

 They consisted of two series the one analytical, the other synthetical. 

 In the former I was ably assisted by Mr. George Macdougald, in the latter 

 by Mr. E-obert Romanes, junior assistant in Professor Cruni Brown's 



* Eead February 19, 1874. See ante, p. 192. 



t Dr. Andrews informs me that he had observed a similar phenomenon when at- 

 tempting to determine the amount of atmospheric gases in sea-water, by boiling it in 

 the Torricellian vacuum after the manner of vapour-density determinations. 



YOL. XXII. 2 P 



