602 WILLIAM LAWTON GOODWIN ON THE 
question then arises, Is the solubility in the water decreased by the presence of 
the salt ? 
SETSCHENOW (Deut. Chem. Ges. Ber., vi. 1461) has examined the effect of 
magnesium, aluminium, and zine sulphates on the solubility of carbonic acid. 
He concludes from his results that in salts of similar structure and amount of 
water of crystallisation, the chemical equivalents are likewise the absorptio- 
metric equivalents. He has also experimented with sodium salts, and finds 
that they fall into two groups with regard to their action on the solubility of 
carbonic acid. (1.) Those which do not combine with carbonic acid, as sodium 
chloride. Solutions of these absorb the gas according to DAuron’s law. (2.) 
Salts which combine with carbonic acid—for example, phosphate of sodium. 
With these absorption increases with strength of solution, but is not propor- 
tional to pressure. 
SETSCHENOW’s examination of sulphuric acid (Peterb. Acad. Bull., xxii. 102) 
gives the following results :—-The coefficient of absorption of the pure acid 
for carbonic acid is almost identical with that of water. On dilution, the 
coefficient diminishes rapidly till an acid of a strength represented by the 
formula H,SO,+H,0 is obtained, after which further dilution slowly increases 
the coefficient. , 
The solubility of ammonia gas has been studied by Raovutt (Compt. Rend., 
Ixvii. 1078), who has obtained the following results :— 
The coefficient for solutions of caustic potash is less than that for water. 
Thus, at 16° C. and 760 mm. pressure— 
100 c.c. water absorbs 60 gms, ammonia. 
, 2425 per cent. potash solution 30 gms. ammonia. 
saturated potash solution 1 gm. ammonia. 
» 
»” red 
From which it appears that the solvent power of the water is decreased by the. 
presence of caustic potash, since 100 c.c. of the 24°25 per cent. solution 
contains more than 50 c.c. of pure water. 
Soda solutions have the same coefficient as potash solutions of the same 
strength (equivalent ?). 
Solutions of sodium nitrate and of ammonium nitrate absorb the same 
volume as equal volumes of pure water. On the other hand, dry sodium nitrate 
absorbs none, while dry ammonium nitrate absorbs a considerable volume. 
Solution of potassium nitrate absorbs more ammonia than pure water, but 
there is no ammonia in the evaporated residue. He formulates his results in 
the general statement: The difference between the coefficient of absorption of - 
ammonia in water and in solutions of a salt is proportional to the weight of the 
salt in a constant volume measured before the absorption of the gas. 
The solubility of chlorine gas in saline solutions does not appear to have 
