THE VOYAGE OF H.M.S. CHALLENGED. 
ooq 
st muling in a bottle of clear hard glass and provided with a good glass stopper, to see 
whether any deposit of carbonate of lime is formed, and in order to identify the places 
whi le the water has already come up to the state of saturation in regard to this com- 
ponent. (3) Alkalinity determinations by the method of Tornoe, as described on pages 
100 and 124. The standard solution of hydrochloric acid could easily be provided in 
large quantities and at a low price, and even when used by itself, i.e., without an 
auxiliary solution of caustic alkali (which probably only a chemist could manipulate 
corrci tly on board a ship), would give valuable approximations in the hands of any 
intelligent man who had been taught to use it in a laboratory. (4) Rough determinations 
of the carbonic acid by means of aurine as an indicator, and the normal hydrochloric acid 
for the alkalinities. I found by experiments made a short time ago that a sea-water 
becomes neutral to aurine, when, by addition of hydrochloric acid, the ratio of surplus 
base to carbonic acid has come down to the value 1 [NaOH] to l - 36 or l - 46 times [C0 2 ]. 
Hence, supposing 1 litre of a sample of sea-water to contain surplus base equal to 
50 mgrms. of carbonic acid as normal carbonate, and 1 litre of the same water, after 
adding aurine and then hydrochloric acid in the cold, required hydrochloric acid equal to 
1 0 mgrms. of carbonic acid before the violet aurine colour gives way to the yellow tint, 
then the total carbonic acid present would amount to (50 — 10) x 14x2 mgrms. And 
a sea-water which does not become violet on addition of aurine, but yellow, is sure to 
contain at least 0'41 x 44 mgrms. of free carbonic acid for every 1 mgrm. equivalent 
of base (meaning £ Xa,0 or,£ CaO, etc.) present as bicarbonate, i.e., for every one mole- 
cule of bicarbonate CO ; , R'H. Hence, if Tornde and Buchanan assure us that all sea- water 
becomes violet on addition of aurine, this in itself is quite compatible with the assump- 
tion that all the samples which they thus examined contained free carbonic acid gas in 
addition to fully saturated bicarbonate. The free carbonic acid must rise to 0'8 mgrms. 
f»r every one mgrm. of C0 2 in the R 2 C0 3 part of the bicarbonate (i.e., for every one 
mgrm. of •‘alkalinity per litre”) before the aurine reaction ceases. Of all the 195 
samples of sea-water which Mr. Buchanan analysed for carbonic acid, only two (Nos. 532 
and 383) came even approximately up to this limit. 
Let seafaring men search for waters which assume a yellow colour on addition of aurine. 
Wherever such water is found a volcanic carbonic acid spring must be close at hand. 
Under my second heading fall such kinds of work as demand a skilled chemist for 
their performance, and it will be convenient to take them up in the order in which they 
appear in my memoir. 
1. Further researches on the Composition of Ocean Salt. — By Forchhammer’s and my 
""'n analv ■ h it is proved that the percentages of the several components are subject to 
..i.'v •di'.dit variations. Apart from the one success with the lime, 1 was not able to trace 
b.vk th- fluctuations to natural causes. Hence new analyses are absolutely useless 
