REPORT ON THE COMPOSITION OF OCEAN -WATER. 
17 
present in it, by repeated digestion in hot neutral carbonate of ammonia and re-ignition. 
From these materials and pure carbonate of lime a kind of sea- water free from potash was 
prepared, and 100 c.c. of it taken for each trial. Two blank experiments gave 0'8 and 
l'O mgrm. of platinum. In the analyses of mixtures of artificial sea-water with weighed 
chloride of potassium the following results were obtained : — 
I. 
II. 
III. 
IV. 
V. 
Mgrms. of platinum due, 
12-2 
26-3 
49-6 
97-6 
103-0 
Mgrms. of platinum found, 
14-0 
28-4 
51 T 
96-7 
102-1 
One hundred mgrms. is about the weight of platinum due from 100 c.c. of natural 
sea-w r ater. Hence the platinum obtained, according to IV. and V., should be liable to a 
positive correction of about 0’9 mgrm. = to about 0'5 mgrm. of potash. But considering 
the general evidence of these (and preceding) trials, I thought I had better simply accept 
the results of the analyses as probably correct to within ±1 per cent, of their value. 
For the reduction of platinum to potash the same atomic weights Pt=198, K = 39, 
were used as in all the previous analyses, although, according to a research lately pub- 
lished by Seubert, the atomic weight of platinum is more nearly equal to 195’0, whence 
K 0 
-=J— = 0'48353. Recalculating trials IV. and Y. with this new factor we have — 
IV. 
V. 
Platinum due, 
96-1 
101-4 
Platinum found, . 
96-7 
102-1 
Error, 
+ 0-6 
+ 0-7 
Instead of, 
-0-9 
-0-9 
I thought I had better adhere to the old factor, and did so. 
Determination of the Soda. 
To this item in my analysis I paid special attention, because I hoped by the exact 
determination of all the salt radicals in my sea- waters to be able to settle finally the 
important question whether carbonate of lime really exists as such in sea-water. This 
question has, I believe, been looked at from an erroneous standpoint by some of the 
chemists interested in it. There have been attempts, for instance, to separate out car- 
bonate of lime directly from sea- water by boiling or by evaporation to dryness and re-solu- 
tion. Neither method could give an absolutely decisive result, because the carbonate of 
lime, supposing it to be obtained, especially in the latter process, might have been formed 
in consequence of the decomposition of the chloride of magnesium, and elimination of the 
(PHYS. CHEV. CHALL. EXP. — PART I. — 1884.) A 3 
