r 



21. Notes from the Chemical 



College. Note No. i.— A new method of preparing 



Merc 



xn 



By Panchanan Neogt, M.A., Premchand Roychand Scholar, 



mid Govervment of Bengal Research Scholar. 



Yvon (Comptes rendus, 76, 1607) obtained mercurous iodide 

 by heating mercury and iodine in a retort on a sand-bath to 250®. 

 Stroman (Berichte, 20, 2818) also got it on a large scale by heat- 

 ing a strong solution of HgNO^ containing a little nitric acid 

 with excess of iodine. Rny (Journ. Asiatic Soc. Bengal, Ixix. pt, 

 ii., 1900, p. 477) has prepared it by the interaction of ethyl iodide 

 on mercurous nitrite. In all these cases the mercurous ioide 

 obtained was of a distinct yellow colour. 



Experimental. 



A sample of isopropyl iodide prepared from glycei'in, iodine 

 and phosphorus was left with a globule of mercury in order to 

 keep it colourless. The iodide remained with the globule of mer- 

 cury for nearly eight months in a dark room unobserved, at the 

 end of which time it was taken out. I was surprised to find 

 beautiful, yellow, shining crystals at the neck of the flask instead of 

 isopropyl iodide in it. Another layer of red crystals of mercuric 

 iodide was found above the layer of the yellow crystals. The 

 isopropyl iodide being very unstable even in the dark evidently 

 liberated iodine, which in the nascent state combined with the 

 mercuiy present forming mercurous iodide, which sublimed gradu- 

 ally during the long interval on the neck of the flask forming large, 

 beautiful, yellow crystals, while a portion of the mercurous iodide 

 was oxidised to mercuric iodide forming the layer of red crystals. 

 The experiment was repeated with metliyl, ethyl and iso- 

 propyl iodides in presence of sunlight, in order to expedite the 

 liberation of iodine by the actinic action of sunlight. In this 

 manner a larger yield of mercurous iodide was secured. The 

 experiment was conducted in the following manner. The iodide 

 was taken along with mercury in a round-bottomed flask, which 

 was corked wit^ a rubber-cork and exposed io strong diffused 

 sunlight. The cork was occasionally removed in order to 

 allow the gaseous products of decomposition to pass away and 

 the contents of the flask were occasionally shaken. As the 

 reaction went on, a yellow deposit was continuously formed, and 

 when the whole of the iodide was used up. fresh iodide was poured 

 in until the whole of the mercury was converted into the yellow 

 compound. The yellow deposit was then transferred into a small 



