ACTION OF SULPHURIC ACID UPON THE AMIDES AND NITRILES. 
465 
experiments are necessary in order to fix the quantity of acid required for the con- 
version of the propionainide, since commercial Nordhausen acid varies considerably 
in composition. If too much acid be employed, the mixture is often perfectly carbon- 
ized, whilst too little acid gives rise to the formation of either sulphopropionic or 
propionic acid. 
If care be taken to regulate the heat so as just to keep up the liberation of carbonic 
acid, the amount of disulphetholic acid may be considerably increased. 
The solid residue in the retort, when cold, is dissolved in water, and treated, as in 
the case of disulphometholic acid, first with carbonate of barium and subsequently 
with carbonate of ammonium. On evaporation the liquid thus obtained furnishes 
two salts, one of which is quite uncrystallizable, and must be separated from the 
other by washing with weak spirit. A crystalline substance remains on the filter, 
which, after two or three crystallizations from hot water, is the pure 
Disulphetholate of Ammonium. 
When deposited from an aqueous solution, this salt forms regular cubic crystals or 
square prisms, perfectly colourless. It is insoluble in alcohol and in ether. In its 
general behaviour this substance differs but little from the corresponding salt of the 
methyl-series, the principal feature of difference being a greater solubility and its 
leaving a carbonaceous residue when strongly heated. 
Disulphetholate of Barium 
crystallizes with regularity in six-sided plates, which generally arrange themselves 
from centres. It is easily formed by heating a solution of the ammonium-salt with 
hydrate of baryta until every trace of ammonia is expelled, and then passing a current 
of carbonic acid through the solution to remove the excess of baryta. It is very 
soluble in water, and stable at a temperature of 180°, but blackens when strongly 
heated in close vessels, ernpyreumatic vapours being at the same time given off. The 
black residue burns with a sulphur-flame. 
Disulphetholate of barium is insoluble in concentrated nitric acid, which does not 
decompose it. It crystallizes from the dilute acid without apparent change. 
After fusion with chlorate of potassium and carbonate of sodium, the filtrate con- 
tains sulphates in solution, proving that there is more sulphur present than is required 
for saturating the barium of the compound. By this method the disulphetholates can 
be distinguished from the sulphopropionates presently to be described. 
0'4490grm., at 170°C., gave 0*3266 grm. of sulphate of barium ; 
0*5045 grm., fused with chlorate of potassium, gave 0*7229 grm. of sulphate of 
barium ; 
which numbers accord with the formula 
C,(H, Ba,) S, O.,. 
