Lerrs & Bhake—The Carbonic Anhydride of the Atmosphere. 149 
(2.) A duplicate experiment conducted in the same manner as 
(1), but the baryta water was 24 times asstrong. The following 
quantities were obtained :— 
Silica,  . : : : : : - 0.0106 grm. 
Alumina and ferric oxide, . : ‘ > = O@Ol7  ., 
Alkaline sulphates, . ‘ : 5 - 0:0025 ,, 
(3.) Seven of the Winchester quart bottles previously used for 
experiments (1) and (2) were each rinsed with 60 c.c. of the dilute 
hydrochloric acid (1 ¢.c. = 0-1 ¢.c. CO,) in several portions: these 
washings were united, evaporated to dryness in a platinum dish, 
and further treated as (1) and (2), when the following quantities were 
obtained :— 
Silica. : : , : : .  0:0020 grm. 
Alumina and ferric oxide, . i >  OOO0OO8 5, 
Lime (CaO), . 5 ; , ‘ 5 OOO2O 5. 
Alkaline sulphates, . ‘ é 5 O00 30, 
Thus baryta water exercises a second action on glass, whereby 
substances are formed which are insoluble in water but soluble in 
dilute hydrochloric acid. 
(4.) A control experiment, in which 200 c.c. of the weak baryta 
water and 240 c.c. of the dilute hydrochloric acid were evaporated 
together to dryness in a platinum dish, and the residue treated as 
in the preceding experiments, using as far as possible the same 
quantities of wash-water in the different filtrations, when the 
following results were obtained :— 
Silica, e : : ‘ ; : . 0:0012 grm. 
Alumina and ferric oxide, . : : SO 000 oie 
Lime (CaO), . ; 6 : g 5  OWOOS 5, 
Alkaline sulphates, . ; i i 5 “MOON 45 
Iu the following table we have collected the results of the 
preceding experiments, after deducting the quantities obtained in 
the blank determinations. It also contains the mean results of 
analyses made of the glass itself—for which we are indebted to 
Messrs. Caldwell & Hawthorne, the honorary demonstrators of the 
chemical department, Queen’s College, Belfast. 
