REPORT ON THE COMPOSITION OF OCEAN-WATER. 
231 
NOTE ON TABLE XIII. 
BY J. Y. BUCHANAN. 
I am indebted to Mr. Murray for the opportunity of perusing Prof. Dittmar’s Memoir, 
and I have read it with the greatest interest. 
In connection with Table XIII., which gives the results of the determinations of 
carbonic acid in sea-water, made at sea, and is an extract from my journal, it is right 
that I should state that the method employed was adopted on my responsibility, as the 
best available at the time. 
From the experiments of Himly and Jacobsen, it was known that sea-water, on being 
boiled, continued to give off carbonic acid until it was reduced almost to dryness. 
It was evident that this was due to some one or more of the saline ingredients, but 
much uncertainty prevailed as to the particular salt or salts to which it should be 
ascribed. In order to be sure of eliminating all the carbonic acid, I proposed to 
acidify the water, boil it, and collect the carbonic acid evolved by absorption in baryta- 
water. In whatever way the carbonic acid might be combined in the water, I believed 
that the compound would certainly be decomposed by boiling with an excess of a mineral 
acid, and I proposed to use sulphuric acid. This method was objected to on the ground 
that the carbonic acid so determined would include all that might be present as bicarbonate 
of lime. The principal object which we had in view in boiling out the gases and in esti- 
mating the carbonic acid, was to determine the nature of the atmosphere afforded to 
the animals living in the water. It was thought that only one half of the carbonic 
acid in the bicarbonate could be looked upon as forming part of the aqueous atmosphere, 
the other half certainly forming part of the mineral constituents of the water. 
In the course of some investigations which I carried out before the Expedition 
sailed, I observed that solutions of sulphate of magnesia and sulphate of lime when 
saturated with carbonic acid did not give it up completely on boiling, but continued to 
give it off till evaporated nearly to dryness. I therefore determined at any rate to 
eliminate the sulphates, which was done by adding a sufficiency of saturated chloride of 
barium solution. The effect of this was to make the water boil quietly and without 
bumping, and to make the carbonic acid come off more quickly, though there was still a 
slight evolution of carbonic acid during the passage of the last half of the distillate. I 
also expected that increasing the quantity of the other chlorides in the water would 
make the chloride of magnesium less likely to decompose on concentration, and I believe 
that it had this effect. 
After the work of the Norwegian chemists and Prof. Dittmar in this field, future 
carbonic acid determinations will doubtless be made by one of their simple and elegant 
