* Se 
-Todine a Reagent for Hydrosulphuric Acid. 125 
“The conclusions that I -_ arrived at by 36.8 experiments, 
are as follows :— 
“Ist. That the best known reagents for beydronohplantié acid are 
subject to great objections, since they do not indicate even-nota- 
ble quantities of this acid, free or combined ; a circumstance that 
explains why its presence has not been Secsonnteuted | in waters 
whose physical properties rank them as sulphureous. 
“2d. That an alcoholic solution of iodine, employed along 
with starch, is a very sensible reagent for hedrossiphtaie’ acid, 
"free or in a state of combination. It can detect, in an undoubted 
manner, (by a comparative examination with commion water,) a 
_ drop of concentrated solution of any of the alkaline hydrosul- 
phates, disseminated in one hectolitre* of- water, although the 
known reagents lose their action when the same quantity is dis- 
seminated in only ten litres.+ 
“3d. That with the tincture of iodine i starch we can re-~ 
cognize infallibly, in the weakest sulphureous waters, in those _ 
where ordinary reagents are useless, not only the presence, but 
also the quantity of hydrosulphuric acid, either free or in a state 
of combination. 
“Ath. That the need processes for determining the pied 
of hydrosul phuric acid, free or combined, are so long and difficult 
that their result is uncertain and incorrect, especially in ti So a 
Waters. possessing’ but little of the sulphureous principle.” 
. Table o the quantity of Hyd manip haere Acid decomposed by | 
quantities of Iodine from ;}, to 10 grains. 
lODiNR, HYDROSULPHURIC ACID. IODINE. HYDROSULPHURIC ACID. 
Weight in 4 Bulk in cubic | Weightin |” Weight in yr in cubic 
PE i Weight in grains. inches grains. - grains. nches 
Ol | 001351 | .003691 | .60 | .08106 99146 
02 | .002702 | .007382 70 09457 25837 
‘03° | .004053 | .011073 80 10808 29528 
‘04 | 005404 | 014764 | 90 | 112159 33219 
05 | 006755 | .018455 4 1.00 .13510 | .36910 
‘06 | 008106 | .022146 2.00 27020 3 
‘40 | 054040 | .147640 00 | 1. 3.32190 
| 50} 067550 | .184550 | 10.00 | 1.35100 | 3.69100 — 
" Hectolitre, about 264 gallons. t Ten litres, about 24 gallons. 
