124 
THE VOYAGE OF H.M.S. CHALLENGER. 
V. — ON THE ALKALINITY OF OCEAN- WATER. 
Th< alkalinity of a sea-water being a measure of its potential carbonate of lime, it is 
important to have as complete statistics concerning it as possible; and I very much 
• _ iv t now, that 1 selected only some 130 samples for the determination of this item. 
The alkalinity of these samples was determined by Torn0e’s method, explained in 
t -• chapter on the Carbonic Acid (p. 10G). 250 c.c. of sea-water were measured off for 
!i analysis, mixed with an excess of standard hydrochloric acid and boiled for twenty 
minutes to expel the carbonic acid. The acid left unsaturated was then determined by 
titration. The standard acid used was a hydrochloric acid, containing ^ X 36 '5 mgrms. 
of pure acid = Ay x HC1 ] mgrms. per cubic centimetre. The standard caustic potash 
was by intention of equivalent strength; the exact volume of alkali equivalent to 1 
of arid was, of course, determined with great care and used in the calculations. 
In ra>-h case the point of neutrality was determined a number of times by zig-zag titra- 
tion, .ind the mean of the last four to six results taken as correct. From the deviations of 
t!i- o jarate results from the mean we conclude that each analysis is uncertain by about 
±005 c.c. of standard acid. Supposing the standard acid required for neutralising the 
ba • prornt to have been 58 c.c. per litre, the “ alkalinity ” was put down as 
ig= 58 mgrms. per litre, which, of course, means that 1 litre of water contains a 
quantity of base, not muriate or sulphate, which would require 58 mgrms. of carbonic 
arid for its conversion into normal carbonate, M0C0 2 . 
As all the waters had before been tested quantitatively for chlorine, we were in a 
on to refer the alkalinity to 55*43 mgrms. of chlorine, meaning 100 mgrms. of 
t"t i - It - ;* and we did so. The results are given in the following Table I. 
fob min I. uivrs the Challenger number assigned to the sample by Mr. Buchanan. 
Column II. names the Station where the sample was collected. 
< lumn III., under “ Depth,’’ gives the depth at which the sample was taken ; surface 
or l*ottom waters, however, are simply named as such. 
Odumn IV. gives the “ alkalinity ” in mgrms. per litre. 
' nun \ . _'iv< - the alkalinity in grins, per 55*43 grins, of chlorine, or per 100 grins. 
; or, in other words, the weight of carbonic acid which is present as normal 
< arbonates (R..CO,) referred to 100 parts by weight of total salts. 
Column VI. gives the laboratory number. 
^ '■ 1 J "l cntri‘ - is enelo-ed in brackets [ ], it means that there is some 
t!i> r« snlts. and that they are not taken notice of in the subsequent 
di«-u**ion. 
**» •*•* *3, W«I adopted nt tho t bg the rentlt of a calculation 1 upon purl of the 77 complete 
•etaraaaljm. I r a know that 56*410 ia a dowr approximation, lmt thi erroi is too small to be of consequence. 
