se i" ez 
mi. Iodine a Reagent Sor Hydrosulphuric Acid. 
Taal 
+e 
v 
tincture of iodine, (it not being among those ordinarily used ;) I 
found that the decomposition of the hydrosulphuric acid by this 
metalloid, was complete and instantaneous, and that one could 
determine, in a.very easy manner, the precise point at which the 
decomposition of the hydrosulphuric acid is achieved, or when 
the iodine no longer enters into combination. I conclude, from 
this fact, that, with a tincture of which I know before hand the 
proportions, I shall be able to ascertain; by the quantity of iodine 
employed to saturate a litre of the sulphurous water, the precise 
amount of hydrosulphuric acid which it contains. i 
“Moreover, I am able to ascertain the quantity of iodine em- 
ployed, without the use of a balance, by the means of an instru- 
ment which I call a sulphohydrometer. This instrument is a 
graduated tube, which allows the tincture of iodine to flow from 
an elongated extremity with a capillary opening, the other ex- 
tremity being closed bya stopper. - 
“'T’o employ the sulphohydrometer, we take a certain quantity 
of the sulphurous water which we may wish to analyze, and 
placing it in a porcelain capsule, add a few drops of a very clear 
solution of starch, and then allow the tincture of iodine to fall 
upon it, drop by drop, from the instrument, previously filled to 
the point marked 0°, and continue the addition so long as no 
change takes place in the color of the water, favoring the reac- 
tion by agitation with a glass rod. So long as there remains t 
smallest trace of hydrosulphurie acid, the iodine disappears a8 » 
fast as it is introduced, and the starch, upon which iodine in @ 
state of combination does not act, gives rise to no coloration of . 
the liquid until the hydrodalghorit acid is completely saturated, 
when the minutest addition of iodine at once strikes a blue color 
with it. We then examine how many degrees of tincture have 
been employed, and knowing the strength of it, we are enabl 
to calculate the quantity of hydrosulphuric acid decomposed pyit. 
‘This method of analysis, independent of its affording results 
of the most accurate character, has the additional advantage of 
being executed in so short a space of time, that one may make 
from fifteen to twenty experiments in less ee one hour, and at 
the same time be perfectly sure of committing no error. It is 
also so easily put into practice, that any physician or intelligent 
person may apply it, and assure themselves daily of the variation 
in the strength of the sulphurous waters caused either by — 
pherie changes or an admixture with rain water. 
