604 Mr. J. Y. Buchanan on Chemical Work 



carbonic acid as an equal bulk o£ fresh water would have done. Further, 

 as might have been expected from the above observations, the amount of 

 carbonic acid contained by surface-waters of the same temperatures 

 increases with the density, and consequently is greater in the surface- 

 water of the Atlantic than in that of the Pacific, the Wo oceans being 

 very markedly distinguished from one another by the different densities 

 of their surface-waters. Thus we have a mean of 0*0466 gramme C0 2 

 per litre in Atlantic surface-water of temperature between 20° and 25° 0. 

 and mean density 1*02727; whilstin the Pacific the mean is 0*0268 gramme 

 in water of 1*02594 mean density • and the mean amount of carbonic 

 acid in Atlantic water of temperature above 25° C. and mean density 

 1*02659 is 0*0409, whilst in the Pacific the corresponding water is of 

 mean density 1*02593, and contains 0*0332 gramme C0 2 per litre. As a 

 rule, other things being equal, the amount of carbonic acid diminishes 

 as the temperature increases ; thus the mean amount of carbonic acid in 

 waters whose temperature was between 15° and 20° was found to be 

 0*0446 gramme per litre, the mean density being 1*02642, whilst we 

 have seen that in the Atlantic the surface-water of temperature above 

 25° O. and of mean density 1*02659 contains 0*0409 gramme per litre. 

 Also there is usually more carbonic acid in waters taken from the bottom 

 and intermediate depths than in surface-water • but if regard be had to 

 the temperature of the water, it will be seen that there is but little 

 difference in the amount in waters of the same temperature from what- 

 ever depth they may have been derived. This seems to indicate that the 

 animal life at the bottom and at great depths cannot be very abundant, 

 otherwise there could hardly fail to be a decided excess of carbonic acid 

 in the deep water, owing to constant production and want of the means 

 of elimination of the gas. On this subject, however, it would be prema- 

 ture to speculate before the determination of the oxygen, from which we 

 may hope for much information. 



I have made a number of experiments to detect the presence of car- 

 bonates in sea-water. If any were present, they should be found in the 

 residues from the determination of the carbonic acid • and I had been in 

 the habit of testing by adding a little acid to them, and invariably with 

 the same result — that carbonates were not present ; at the same time it 

 appeared to me to be very unlikely that such should be the case, when 

 there is plenty of carbonate of lime in the shells of the animals living 

 and dying in it, and also plenty of carbonic acid in the water to dissolve it. 

 It was also not improbable that the very considerable amount of sulphate of 

 baryta in the residues might disguise the effervescence. I therefore evapo- 

 rated a separate portion (about 150 cub. centims.)of the water in aplatinum 

 dish to dryness, removed the soluble salts with a little water, and added a 

 few drops of strong hydrochloric acid, which was allowed to flow slowly 

 over the inner surface of the dish, when even the smallest trace of car- 

 bonates could be detected by the appearance of minute bubbles on the 



