Iodine a Reagent for Hydrosulphuric Acid. 123 



Art. XIII. — The employment of Iodine as a reagent for Hydro- 

 sulphuric Acid ; by M. Alphonse du Pas^uier. 



TO THE EDITORS OF THE AMERICAN JOURNAL OF SCIENCE. 



Gentlemen, — The original of this article was published in the 

 March number of the Annales de Chimie et de Physique, and 

 the importance of its being generally known to those who devote 

 any of their time or attention to the investigation of our mineral 

 waters, many of which are more or less impregnated with hydro- 

 sulphuric acid and the alkaline hydrosulphates, has induced me 

 to transmit to you, for publication, a translation of such parts as 

 explain the method of employing the reagent in question, and 

 the conclusions that M. Al|)honse has arrived at by his varied ex- 

 periments. 



The sulphohydrometer that is described, is of easy applica- 

 tion, and enables one to obtain very accurate results in a short 

 space of time, particularly when use is made of a table that I 

 have calculated and annexed. 



As regards the strength of the tincture of iodine, that is alto- 

 gether optional with the individual who employs it ; it being only 

 requisite to have a knowledge of the amount of iodine contained 

 in a measured portion of the liquid. I should propose, as most 

 convenient, that each division on the sulphohydrometer should 

 answer to y'^ of a grain of iodine, and a subdivision to jl-^. 



Yours respectfull)^, J. Lawrence Smith, M. D. 



Paris, Sept. 20, 1840. 



" To determine the -proportion of hydrosulphuric acid, either 

 free or in combination in sulphureous waters, is an operation at- 

 tended with considerable difficulty, and of which the results are 

 far from being certain. All the methods employed to arrive at 

 this end, comprising even the process of M. Grotthuz, (the em- 

 ployment of ammoniacal nitrate of silver,) adopted by M. An- 

 glada, and the ge-nerality of the chemists of the present day, pre- 

 sent great difficulties of detail, and are, as has been demonstrated 

 in my first memoir, subject, to gross errors, particularly when we 

 obtain a sulphuret more or less impure ; and moreover when the 

 quantity of hydrosulphuric acid is very minute they cease to act. 



"In my researches upon the waters of Allevard, the uncer- 

 tainty of these methods, made me desire to discover some process 

 more satisfactory, when, employing as a reagent the alcoholic 



