HYPOSULPHITE AND TRITHIONATE OF POTASH. 193 
to the filtered liquor ; it is again heated a little, and the so- 
lution furnishes on cooling perfectly pure, beautiful quadri- 
lateral prisms. Their taste is slightly saline and bitter. On 
exposure to heat, they afford sulphurous acid, sulphur, and 
leave a residue of 64.36 neutral sulphate of potash ; they 
are neutral, and dissolve readily in water. The aqueous 
solution is decomposed by sulphuric and nitric acids, with 
deposition of sulphur and disengagement of sulphurous acid. 
Hydrochloric acid does not decompose them ; they do not 
give precipitates with solutions of lime, barytes, iron, zinc, 
magnesia, nickel, &c. They decolorize the red sulphate of 
manganese, but do not act on a solution of sulphate of cop- 
per ; they precipitate the salts of protoxide of mercury 
black, those of the duetoxide blue, and give with the ni- 
trate of silver a yellowish-white precipitate, which soon 
becomes black. The salt in question consequently pos- 
sesses all the properties of the trithionate of potash. 
The mother-ley of the crystals just described becomes 
turbid, and deposits sulphur when exposed to a tempera- 
ture which would not decompose a solution of the trithion- 
ate of potash ; and on adding some concentrated alcohol, 
deposits a salt in which crystals are perceptible, the form 
of which differs from that of the trithionate. 
M. Gelis informs me that these crystals must be the te- 
trathionate, since this salt is likewise produced by the reac- 
tion of sulphurous acid on the hyposulphite. 
When I became aware that M. Gelis was also investi- 
gating this reaction, I had only been able to determine ap- 
proximately the quantity of sulphurous acid absorbed by a 
given weight of hyposulphite. I had observed, without, 
however, being certain of my results, that the absorption 
took place in the proportion of 
2 (S* 02 K0) + 3 (SO*). 
A deposit of sulphur is always formed when concentrated 
liquors are acted upon. It became important to ascertain 
whether this deposit took place when dilute solutions were 
