313 Intelligence and Miscellaneous Articles, 



ON THE IODIDE OF AMIDIN. BY M. J. L. LASSAIGNE. 



In 1 833 the name of iodide of amidin was given by M. Lassaigne 

 to the compound of iodine and the internal and soluble portion of 

 fecula ; the properties of this singular compound were then stated, 

 and the decolorating power of heat was mentioned. 



The results obtained by M, Lassaigne induced him to believe that 

 this compound of iodine and amidin was soluble in water, contrary 

 to the opinion of some chemists, who, subsequently to his experi- 

 ments, endeavoured to show that this blue compound is merely sus- 

 pended in the liquid in a state of extreme division. The observa- 

 tions made by M. Lassaigne are confirmed by those which he has 

 since made : 



1st. A solution of iodide of amidin prepared in July 1833, by 

 pouring a solution of iodine into the soluble portion of fecula, ob- 

 tained by treating the bruised grains with cold water, was placed in 

 a dark closet. This solution, examined monthly to the present 

 time during four years, has not yielded any deposit ; it has always 

 had the appearance of an homogeneous solution, equally coloured 

 throughout of a fine indigo blue ; and it has always had the aj^pear- 

 ance of freshly prepared iodide of amidin. The long time which 

 this solution has been kept, without any sensible diminution of in- 

 tensity, proves that it exhibits all the properties of a true combina- 

 tion ; for a simple solution of amidin in water underwent a complete 

 decomposition in some weeks, or at any rate it lost the property 

 of colouring a solution of iodine blue. 



2nd. The action of cold upon the above-described solution of io- 

 dide of amidin corroborates the opinion which has been expressed 

 of its nature. It was exposed in the winter to a temperature of about 

 8° Fahr. ; it solidified and became of a black-blue. During one night 

 in January in which the temperature was about 10° Fahr., it was 

 exposed to the air, and became a solid mass, of a brownish yellow 

 colour, which it lost as the temperature became higher, and returned 

 to a deep blue ; placed in a warm room, it gradually liquefied, and 

 during this change the iodide of amidin was deposited in flocks at 

 the bottom of the bottle, the water remaining colourless. 



This coagulation of the iodide of amidin by the action of cold, and 

 its separation from the water which held it in solution before conge- 

 lation, is attributed by M. Lassaigne to the cohesion of its molecules, 

 which modified its affinity for water; by heating this fluid, in 

 which the iodine was suspended and not dissolved, to about 60° Fahr., 

 it re-dissolved and formed a fine blue coloured solution, and possess- 

 ed all the characters which it had before congelation. 



This observation, added to the former, leaves no doubt that iodide 

 of amidin is really soluble in water at common temj)eratures, and 

 that it evidently separates when a physical cause produces the ap- 

 proach of its molecules, or a chemical action determines its union 

 with other bodies, which then render it insoluble in water. 



It was found that a freshly prepared solution of iodine did not as- 

 sume the brownish yellow colour, which the long prepared solution 

 did when exposed to a low temperature. This difference is attri- 



