Letts & Bhaxe— The Carbonic Anhydride of the Atmosphere. 155 
and BaO by the usual methods. The following quantities were 
obtained :— 
Silica, . 2 - 0°0575 grm. 
Barium oxide, - 0:0586 
9 
The ratio 5 SiO,:2 BaO requires the proportion 575: 586. Not 
being satisfied that the baryta had remained in contact with the 
silica sufficiently long for complete action, the following experiment 
was performed :—Iixcess of pure silica dried at 100° C., but not 
ignited, was placed in a paraffined bottle, and the latter filled com- 
pletely with the weak baryta solution (1 c.c.=0'l¢e.c. CO, at N.T.P.). 
The bottle and its contents were rotated with a turbine for three 
days. A portion of the liquid was then filtered off and titrated 
with dilute hydrochloric acid (of equivalent strength to the baryta 
water). As in previous experiments the point of final decoloriza- 
tion of the phenol-phthalein used as colour indicator was difficult 
to determine. 20 c.c. required 6:3 c.c. of theacid. On determining 
SiO, and BaO in some of the clear fluid we obtained :— 
Silica, . 6 - 0°0446 grm. 
Barium oxide, - 07055 ,, 
The ratio 2 8i0,: BaO requires 0°0446 : 0:0568. 
This experiment was unsatisfactory, as, for some reason which 
we cannot explain, the silica obtained was quite black after 
ignition, even in oxygen, and the colour did not change on boiling 
with aqua regia. A final experiment conducted like the preceding 
one gave the following results after seven days rotation of the 
vessel containing the baryta water and silica. 20 o.c. required 
2°7 c.c. of standard acid. A portion of the solution contained— 
Silica, . : - 0:0275 grm. 
Barium oxide, - 0-0150 
9 
The ratio 4 810, : BaO requires 0°0275 : 0:0175. 
Quite different and very -curious results were obtained by 
allowing the silica to remain in contact with a stronger baryta 
solution, viz. decinormal. 
On analyzing such a solution which had been in contact with 
silica for a year in a paraffined bottle, the following results were 
obtained :—25 c.c. when titrated with standard acid and phenol- 
phthalein required 18°1 c.c. decinormal acid. 
SCIEN. PROC. R D.S., VOL, IX., PART II. N 
