1 1^ Dr. Apjohn oji a new Compound of Iodide of Potassium, 



To a gallon of cinnamon water *, first reduced nearly to 

 32°, add four ounces of iodide of potassium and forty grains of 

 iodine previously dissolved in a minimum of cold water. Upon 

 the instant of admixture the solution becomes quite turbid, 

 owing to the production of a yellowish sediment, and this in 

 less than a minute becomes crystalline, and then gradually 

 subsides. The supernatant solution, which appears almost 

 entirely deprived of iodine and oil of cinnamon, is now drawn 

 off with a siphon, and the crystals and residual fluid thrown 

 upon a single filter, which, when sufficiently drained, is en- 

 veloped in several folds of blotting-paper, and transferred to a 

 chalkstone, where, by the absorbent powers of the latter and 

 the occurrence of spontaneous evaporation, the product is 

 rendered perfectly dry and pure. With the quantities stated 

 above 60 grains of the compound are obtained. A tempera- 

 ture at or very close to 32° is necessary to the success of 

 this process. At 40° the brown powder already noticed is 

 alone produced, and in much diminished quantity. This 

 brown sediment, however, is identical with the crystalline 

 product, for it may be converted into crystals simply by re- 

 duction of temperature, and I have even found it to undergo 

 the same change when collected on a single filter, and set to 

 dry on a bibulous stone at the temperature of 45°. 



The crystals are capillary quadrilateral prisms, without 

 pyramidal terminations. They are of a beautiful brown or 

 bronze colour, and have a strong metallic lustre. Their taste 

 is extremely hot and pungent, resembling closely that of oil of 

 cassia, but partaking also of that of iodine. In alcohol and 

 asther they are readily dissolved, and from these solvents they 

 are again deposited with their original appearance upon the 

 occurrence of spontaneous evaporation. They are decom- 

 posed by water, which extracts from them iodide of potassium, 

 and causes the separation of oily drops of a dark colour, which 

 are either a mechanical mixture or a peculiar compound of 

 iodine and the oil of cinnamon. This action of water, how- 

 ever, is greatly diminished when it is close to the freezing 

 point, and appears altogether prevented when a certain amount 

 of iodide of potassium is present. 



When heated to 82° the crystals melt into a dark liquid, 

 from which upon cooling the original substance is reproduced. 

 When heated beyond its melting point iodine and a vapour 

 smelling strongly of oil of cinnamon sublime, and iodide of 

 potassium is left behind, mixed usually with a little carbon 

 resulting from the decomposition of a portion of the oil. 



• This water should be prepared by introducii)g into a still one pound 

 of cassia bark and two gallons of water, and drawing off one gallon. 



