1 GO 
THE VOYAGE OF H.M.S. CHALLENGER. 
III. — On the Coefficients of Absorption of Nitrogen and Oxygen. 
In interpreting the results of the gasometric work summarised in the above tables, it 
is expedient to begin with the carbonic acid, because it can be dismissed in a few 
words, It i' proved by the analyses of the Norwegian chemists, and confirmed by my 
own work (as reported in the chapter on carbonic acid), that the quantity of carbonic 
acid present in a litre of sea-water rarely exceeds, and often falls short of, what is 
required to convert the “free” base into bicarbonate. This explains what Jacobsen and 
Buchanan found so difficult to understand, namely, the fact that in the expulsion of 
sea-water gases by boiling the proportion of carbonic acid which goes into the bulb 
d' pends very largely on the circumstances under which the process is conducted. It is 
of course the greater the longer the boiling is continued, and perhaps, we may add, the 
less the pressure in the gas bulbs, although a diminution of this pressure necessarily 
involves a lowering of the temperature of the boiling liquid, and consequently so far a 
diminution in the dissociation tension of the dissolved bicarbonate. But one thing is 
clear : the carbonic acid enclosed in Mr. Buchanan’s gas-tubes must include the whole 
of the carbonic acid which was present in the respective waters in the free state ; and, 
roii.-wqucntly, it is worth while to take up some of those cases in which the carbonic acid is 
• xceptionally high, in order to form an idea of the proportion of free carbonic acid that a 
M-a-water may actually contain. The following is a selection of cases where both the total 
volume of absorbed gas and the carbonic acid per unit-volume of gas assume high values: — 
No. of Water. 
1009 
1024 
771 
974 
1096 
We need not go further in order to sec that even in these deep-sea waters the absorbed 
< arl)onic acid falls far short of what would correspond to, say, 2 per cent, of the greatest 
qu i ut it y which would Is- absorbed under 760 mm. of pressure from an atmosphere of pure 
carbonic acid. 
In onlcr to understand the values obtained for the oxygen and nitrogen, we must 
know tie value of the coefficients of absorption of these gases for sea-water at the 
i q • v> t' mperatures. At the time when I made my preliminary investigations these 
: ’"iiits w* ■ p unknown. We had at our disposal only the corresponding values for pure 
r. a.- d' t rtninod by Bunsen. I accordingly decided upon investigating this matter, 
I n.it i rally began with a series of experiments with pure water, so as to have Bunsen’s 
r ’’heck upon my work. What was meant to form a mere preliminary to the 
II. 8. Carbonic acid per litre in c.c. at 0° and 760 mm. 
2875 I 2850 11 "6 
2225 
2325 
3125 
2900 
11-5 \ 
13 "5 ( Bottom 
14- 3 
15- 8 
Waters. 
