116 
TIIE VOYAGE OF H.M.S. CHALLENGER. 
Influence of Sulphates on the affinity of Water for Carbonic Acid. 
P> t'. »r< tabulating the results of the few analyses that were made, I will report shortly 
• >n a few attempts to inquire, quite directly, into the alleged influence of sulphate of 
magnesia on the affinity of water for carbonic acid. 
E t L 28 grms. of specially purified Epsom salts were dissolved in water to 
1 litre. 
23.V2 mgrms. of recently ignited pure carbonate of soda were dissolved in water and 
dilut' d to 100 c.o., in order to obtain a solution of which 1 c.c. should be equivalent to 
O’OGS mgrm. of carbonic acid. 
250c.c. of the magnesia-salt solution were mixed with 25 x L_ o 9 ~ mgrms. of hydro- 
chloric add and boiled under an inverted condenser in a current of air, until the latter, as 
it came out above, failed to cause the slightest turbidity in baryta-water. The liquid was 
then allowed to cool in the ensured absence of carbonic acid, 10 c.c. of the carbonate of 
-•"ft solution run in, the boiling in a current of air resumed, and the carbonic acid thus 
lib' rated collected in the vacuum flask charged with baryta-water. Three such experi- 
ments were made ; the carbonic acid found was 
10‘S2 1 0*37 10'18 mgrms. 
Accordingto calculation, this should be 9*68. Thus it appears that under the circum- 
st met ' a solution of sulphate of magnesia, containing about as much magnesia as sea-water 
1 eon-a-qucntlv twi» ' a- much Bulphuri<- acid), does not retain any carbonic acid. 
This time the liquid operated upon, in addition to the sulphate of magnesia and 
chloride of sodium, contained about 15 x mgrms. of free hydrochloric acid, that is, 
•at 25 mgrm of hydroehloric acid. Hut this minute quantity of acid is not likely to 
d v influenced the 7000 mgrms. of Epsom salt and the 250,000 mgrms. 
of water in their action on the carbonic acid. 
1 : i 't < .a ider it nccc- iry to specially prove this, or to extend the inquiry to the 
- e of u!j Late of lime solutions under similar conditions, but preferred to ascertain 
■her eithei olution, or perhaps even pure water, at ordinary temperatures, contains 
mdl fi net ion of it - absorbed carbonic acid in a state of combination more 
‘ ■ ■ iii that of mere absorption. 1 took 300 c.c. each, of pure water, solution of 
!■: lution of gypsum r q»ertiv< ly, and, in each case, after having saturated 
5 ; ‘ v. b , ! d v. til carbonic acid, shook it repeatedly with several times its volume 
