REPORT ON THE COMPOSITION OE OCEAN-WATER. 
113 
firmation of wliat has been previously found by others. A mixed precipitate of carbonate 
and sulphate of baryta does not yield the whole — and may not yield any — of its carbonic 
acid on treatment with hydrochloric acid ; the cause being no doubt that such a precipi- 
tate contains a double compound of sulphate and carbonate undecomposable by acids. 
In the following experiment (No. 4) the carbonic acid was eliminated by chloride of 
barium as far as possible ; the residue, after cooling, was taken out of the flask and dis- 
tilled in vacuo to as near dryness as practicable, no air from without being admitted. 
The distillate ran into measured standard baryta, so that the carbonic acid in it was 
amenable to titrimetric determination. 
Obtained, mgrms. per litre, of carbonic acid by barium chloride under inverted condenser, 
current of air as usual, ......... 44-4 
By distillation of residue in vacuo, ........ 200 
Total, . 64 - 4 
All the loose carbonic acid, and, besides, 12 ‘6 mgrms. of the 57 ’2 mgrms. of the carbonic 
acid of the normal carbonates were recovered. 
In the following two experiments the water was distilled with chloride of barium “ in 
vacuo ” without preliminaries : — 
Experiments, ...... 
• ( 5 ) 
( 6 ) 
Water taken, ....... 
200 c.c. 
200 c.c. 
Hydrated barium chloride added, . . . . 
3 - 5 grms. 
3 - 5 grms. 
Carbonic acid obtained, reduced to mgrms. per litre, 
44-4 
38-3 
Loose carbonic acid (mgrms. per litre) calculated, 
51-8 
51-8 
The results substantially confirm those of experiments (1) and (2) above. But none 
of these experiments do full justice to the method of Buchanan, who distils his mixture 
under ordinary pressure, and consequently at higher temperatures than can have 
prevailed in either No. 5 or No. 6. I therefore decided upon carrying out a few distilla- 
tions in the following manner : — A measured volume of the water, after addition of an 
excess of solid chloride of barium, is distilled in a current of air under ordinary pressure, 
and the distillate received in a flask connected by air-tight joints, on the one hand with 
the exit-end of the Liebig’s condenser, on the other with a large flask previously charged 
with a sufficiency of baryta-water, and evacuated. A glass stop-cock at the entrance of 
the vacuum flask serves to regulate the flow of gas into the latter. The distillation is 
carried on to as near dryness as possible. A part of the carbonic acid liberated goes 
straight into the vacuum flask, and is there absorbed by the baryta ; the rest remains 
absorbed in the distillate. To recover it, the flask containing it is joined on to the 
bottom end of the inverted condenser in Classen’s apparatus, the carbonic acid expelled 
(PHYS. CHEM. CHALL. EXP. PART I. 1884.) A 15 
