100 
TIIE VOYAGE OF H.M.S. CHALLENGER. 
u hi].*. Before I resumed it, T had, through the kindness of the Editor of the Challenger 
lb ports, wme into possession of a copy of TornOe’s excellent memoir on his and his 
. ..!l;iln>r;iti>rs’ chemical work in connection with the Norwegian expedition.* In it I found 
a \ i v simple method for the determination of tin* alkalinity, which so far had always 
. hal' d my grasp, and also a method for the total carbonic acid, which certainly seemed 
. a ' i .• r <>f application than the one I had marked out for myself. I at once decided upon 
t. 'iing these two methods before doing anything else. Neither of the two methods is 
new. hut this, far from detracting from, rather adds to, TornOe’s merit. 
Account of tlic Norwegian Methods. 
The Alkalinity is determined simply by titration with dilute standard acid and 
alkali in the heat, using an vine as an indicator, which marks an alkaline reaction by a 
violet, an acid by a yellow, colour. TornOe’s numbers show, and a few experiments of 
my own confirmed his result, that it is possible by means of this method, even when 
applied to solutions containing magnesia salts ( e.g ., sea-water), to obtain sufficiently 
e. m-t nt results. I found, however, that on prolonged boiling of sea-water in glass, 
. 1 1 " 1 1 g 1 1 of tlm alkali of the glass is dissolved to render the point of saturation somewhat 
indistinct, and I was thus led to operate in Berlin basins, which proved sufficiently 
resistant 
But constant results arc not necessarily correct results. I considered it quite 
i l.h- that in tin- case of magnesia-salts, at least, the point of aurine- neutrality might 
1 »- oie thing, and the point of true chemical neutrality another. To settle this doubt 
I prepared perfectly neutral sulphate of magnesia by dissolving the ordinary pure salt 
in v iter, adding a little sulphuric acid, and precipitating part of the dissolved salt by 
> i • ! it i • m <>f -'long alcohol. The precipitate was washed with strong alcohol until the last 
; - were ah-olut' 1 \ free from acid, and the salt then dried between blotting paper. 
250 c.c of an aqueous solution of such -alt . fully equivalent in regard to its percentage 
of magnesia to the same volume of Bea-water, when tested in the heat (in a porcelain 
basin) by alternate nt ition (in the presence of aurine) with decinormal hydro- 
■ id and d'-einorinal potadi, proved absolutely neutral, showing that the method 
for tin determination of even small quantities of free magnesia or acid in 
magnesia salt. 
To make rare of everything I made similar trials with solutions (equivalent to 
.1 w .it. r) of pup common salt, and incidentally made a singular observation which I 
:• i u. rtli |. -cording. Ordinary pure chloride of sodium was further purified by 
tie- !• -t proportion of water and reprocipitation with hydrochloric acid. 
* ' K 1 1 - ■ 1 1 1 1 n, 187 H, ri,< mi, Chrinliania. Text in Norwegian and in English. 
