REPORT ON THE COMPOSITION OF OCEAN-WATER. 
19 
the reaction to be accomplished. During the first dozen or so of determinations, the 
perfect neutrality of the residue was ascertained by solution in water and application of 
litmus paper ; but we soon became convinced that the balance alone afforded a sufficient 
test. Special experiments with pure substances having shown that sulphate of magnesia, 
when diffused throughout a large mass of sulphate of soda, remains unaltered at tempera- 
tures at which the salt by itself would lose acid, we began to allow a somewhat higher 
temperature in the ignitions, and thus saved a good deal of time. 
Before the process was applied to the Challenger specimens, it was tested by means 
of synthetically prepared artificial “ sea-water.” In this water (which was far more con- 
centrated than any natural sea- water) the “ total sulphates,” as calculated from the 
synthesis, happened to come to exactly 10 per cent, of the weight of the water. 
(1) (2) (3) * 
Water taken, in grms, . . 3 - 276 10'614 3-259 
“ Total Sulphates ” found, in grins, . 03271 1 ’0633 0-3256 
In the sulphates from (1) and (2) the sulphuric acid was determined by precipitation 
with chloride of barium. 
(1) 
(2) 
Barium sulphate obtained, 
0-5476 
1-8058 
Sulphur trioxide found, 
0-1880 
0-6199 
Sulphur trioxide demanded by synthesis, 
0-1914 
0-6200 
Supposing the corresponding determination to have been made for an otherwise 
analysed sea- water, the quantity of sulphur trioxide found divided by 80 should give the 
number of equivalents of base present, and its excess over the sum of the numbers of 
molecules of sulphur trioxide and chlorine should furnish in a very direct way a value 
for the “alkalinity” of the water. Unfortunately the baryta process is accompanied by 
too many sources of error and uncertainty to be safely available for this purpose. For a 
time I hoped to be able to give it a higher degree of precision, by precipitating a large 
weight of specially prepared total sulphates with a small excess of standard chloride of 
barium, and determining the small weight of baryta in the filtrate gravimetrically ; but a 
number of test experiments, made with mixtures synthetically prepared from known 
weights of pure sulphate of soda and pure magnesia, did not exhibit the extra high 
degree of precision for which I had hoped. I therefore returned to the original idea of 
basing the calculation of the soda on the weight of the total sulphates themselves. To 
give an example, I extract from my preliminary investigations the calculation of 
“Water 924. ”t The quantity of lime was left uncorrected. 
* Chlorine was sought for in the sulphates but not found. 
t Laboratory number 45. 
