29 
6-— ALKALINITY. 
The determination of this character gave me a great 
deal of difficulty. 
Two methods were adopted :—One, by titrating in the 
cold with standard acid in the presence of an indicator 
unaffected by carbonic acid: the other, by adding a known 
volume of acid, boiling off the carbonic acid, and estimating 
the excess of acid by titration with standard alkali. 
By neither method could really accurate results be 
obtained, owing to the difficulty of finding an indicator 
which would give a sharp end point in such a dilute 
solution as sea water. 
Various indicators were employed — methyl orange 
phenolphthalein, and aurine—but constant end points could 
not be obtained. 
Each method will now be considered separately. 
(a.)—Drrecr TrrRation. 
100 cc. of the water was mixed with just enough 1 
per cent. solution of methyl orange to have a percep- 
tible colour, and standard sulphuric acid (about ;4;) was 
run in till a distinct pink colour was produced. This 
was then titrated back with standard alkali (KOH), 
and so by a series of zigzag titrations a number of 
end points were obtained. Unfortunately these were 
by no means uniform, as each was a trifle higher than 
the last, so that at the end of about ten end point 
determinations by this method the amount of sulphuric 
acid required was found to have increased about 1:0 ce. 
Idid not continue after this point as the value was be- 
coming absurdly high; imdeed, I think the first end 
point must be more nearly correct than any sub- 
sequent one. 
