4-98 Intelligence and Miscellaneous Articles. 



vented by forming round the body a sufficient pressure of an elastic 

 fluid of the same nature as that which is to be disengaged. It is 

 thus in the curious experiment of Hall ; carbonate of lime was fused 

 at a very high temperature, without being decomposed, under the 

 influence of a sufficient pressure of carbonic acid. 



Jnn.de Ch. et de Ph. Ixiii. 219. 



PREPARATION OF IODINE. BY M. BUSSY. 



The process of extracting iodine generally followed, and which 

 consists in decomposing the mother- waters of kelp by means of con- 

 centrated sulphuric acid, is well known to be liable to variable re- 

 sults, on account of a portion of the iodine coming over in the state 

 of hydriodic acid and chloride of iodine, so that in either case there 

 is always a considerable loss. 



To avoid this inconvenience, M. Soubeiran proposed to preci- 

 pitate the iodine from the mother-waters by means of sulphate of 

 copper, and afterwards to decompose the iodide of copper by per- 

 oxide of manganese at a high temperature*. But this process re- 

 quires minute attention and much precaution to separate the whole 

 of the iodine existing in the mother-waters, and we do not believe 

 that it has ever been employed in any manufactory. 



These circumstances induce me to publish a far more simple me- 

 thod, which has been lately employed by some manufacturers of 

 iodine ; it was discovered (if we are rightly informed) by M, Bar- 

 ruel, director of the chemical works at the Faculty of Medicine ; it 

 consists in precipitating the iodine of the mother-waters of kelp by 

 a current of chlorine. 



In this process the mother-waters are first to be evaporated to dry- 

 ness, and to the residue there is to be added a tenth of its weight of 

 powdered peroxide of manganese; the two substances are to be per- 

 fectly mixed, and subjected to a dull red heat in an iron vessel, 

 frequently stirring them ; the object of this calcination is to convert 

 the sulphurets and hyposulphates, of which the mother-waters con- 

 tain a large quantity, into sulphates. It is extremely easy to deter- 

 mine when these compounds are converted into sulphates by taking a 

 small quantity of the calcined matter and pouring upon it an excess 

 of sulphuric acid. It ought not to yield, when the conversion is per- 

 fect, either sulphuretted hydrogen or a deposit of sulphur. If violet 

 vapours are disengaged during the calcination, the heat must be 

 lowered to avoid loss. When the sulphurets are decomposed, the 

 residue is to be dissolved in a sufficient quantity of water to give a 

 solution of sp. gr. 1-333 j through this solution there is then to be 

 passed a current of chlorine gas, taking care to stir it constantly 

 with a glass rod : the liquor becomes of a deep brown colour, after- 

 wards turbid, and deposits iodine in the form of a black powder; it 

 is to be collected and distilled in a glass retort, in order to procure 

 it in crystals. The only difficulty in this process is to determine 

 the point at which the action of the chlorine should cease, that no 



* Journ. de Pharmacie, torn. ii. p. 411. 



