Action of Iodine upon Sulphides. 153 



XV. — Behavior of Natural Sulphides with Iodine and 

 other Reagents. 



BY H. CAERINGTON BOLTON, PH.D. 

 Bead March 18, 1878. 



In a paper on the " Application of Organic Acids to the 

 Examination of Minerals," presented to the Academy about 

 a year ago,* we endeavored to show that citric (or tartaric) 

 acid and potassium nitrite can be advantageously added to 

 the usual list of dry reagents employed in the determination 

 of minerals. Owing to the facility with which the latter re- 

 agent is decomposed by the former, nitric acid can be carried 

 practically in the solid form ; hydro-potassium sulphate, al- 

 ready in usef, furnishes sulphuric acid in a solid state ; and it 

 remains therefore to provide for hydrochloric acid, or chlorine. 

 The alkaline chlorides, however, resist the action of organic 

 acids ; and a few experiments with easily decomposing sul- 

 phides yielded only negative results. Iodine, on the other 

 hand, while less powerful than chlorine, possesses similar 

 properties, and in aqueous solution it attacks many minerals, 

 giving rise to characteristic phenomena. 



The employment of bromine in analytical operations ^ has 

 already demonstrated its power in decomposing natural sul- 

 phides ; and it is precisely with these minerals that the most 

 satisfactory results are obtained by the action of iodine. 



The specimens named below are the same as those whose 

 source and condition have been described in the paper referred 

 to. The method of examination is exceedingly simple ; the 

 minerals in fine powder are placed in test tubes, a small 

 quantity of pulverized iodine is added, and then water poured 

 on ; after standing in the- cold for some hours (usually over 



* Annals N. Y. Acad. Sci., Vol. I, p. 1. 



t Distinction of Natural Sulphides by Risulphate of Potassa ; E, Jannettaz (Trap si , from. 

 Compte Rendu 1 . Am. Chem., IV, 450. 

 JP, Waage; Zeitschr. anal. Chem., 1871, 



