167 
other known acid of sulphur is decomposed in the cold by a 
mineral acid into sulphur and sulphurous acid. Another 
portion of the fluid was then taken, diluted with water, 
acidulated with hydrochloric acid and chloride of barium 
added. No precipitate whatever formed, proving the absence 
of sulphuric acid. This test has to be done quite rapidly, as 
after a few seconds sulphur begins to be separated, recogniz- 
able when in small quantity by the peculiar opalescent 
appearance it presents. A third portion of the fluid was 
acidulated with hydrochloric acid, boiled so as to decompose 
all polysulphur acids, which in the case of hyposulphurous 
acid cannot be accomplished in less time than two or three 
weeks. As the precipitated sulphur does not settle very 
quickly, the fluid was shaken with a small piece of bright 
metallic copper which rendered it clear almost immediately, 
so that it could be filtered and tested for sulphuric acid. A 
heavy precipitate was obtained with chloride of barium, 
proving the presence of this acid in large quantity and 
beyond doubt. This sulphuric acid, though not present in 
the original fluid, was produced therefore by the decomposi- 
tion of a sulphur acid, and judging from the syathesis of 
these acids, this must have been trithionic acid. 
28,0, + 380, = 28,0, +S (Preparation.) 
8,0, =SO,+S0,+8 (Decomposition.) 
.We have therefore present in the fluid, after acting with 
sulphurous acid on metallic zine, SOz, S202, S3Os, §, 
ZnO, ZnS, a trace. I may mention here that a solution of 
hyposulphite of soda treated with sulphurous acid turns, 
especially upon heating, first yellow, then brown, sulphur 
separates, and trithionic acid is formed. The change of 
color in the original experiments therefore indicates the 
point when trithionic acid is beginning to be formed. The 
reaction may be represented in the following way:— ° 
1, 2Zn + 380, = ZnO,SO, + Zn0,8,0, 
2. 28,0, + 380, = 28,0,+S8S 
3. (SO, + S=8,0,) 
4, (580, +S = 28,0,) 
The result being ZnO,SO%; ZnO,S20. ; ZnO,8;0s; ; be- 
