Intelligence and Miscellaneous Articles. 239 



ocean. In order to examine the nature of these rocks, some frag- 

 ments were detached from the surface, to which several of the ma- 

 rine plants remained attached. 



The substance which constitutes these rocks possesses consider- 

 able cohesion ; externally it is yellowish- white, and internally chalk- 

 white. When dried in the air, it has the appearance of moderately 

 hard chalk, and is friable. Its porosity having occasioned the ab- 

 sorption of a small quantity of sea-water, it retained a portion of its 

 salts ; superficially this rock has a saline taste, which does not exist 

 at the depth of about one inch and a half to two inches. 



The unquestionable existence of iodine, in the state of iodide of 

 sodium in the greater part of marine plants, and its absence from 

 sea-water, as proved by the experiments made by M. Gualtier de 

 Claubry in 1813, and those since published by Davy, induced the 

 author to search for this element in the rock on which the plants 

 grow. 



About 462 grains reduced to fine powder were treated with cold 

 alcohol of 90 per cent, and afterwards with water. These two 

 liquids, submitted separately to evaporation, left a slight dirty 

 white residue, weighing only a small fraction of a grain ; this was 

 redissolved in water and found to be chloride of sodium, with traces 

 of sulphate of soda and of lime. The presence of an iodide in this 

 residue could not be detected either by solution of nitrate of silver 

 or solution of starch, either in contact with concentrated sulphuric 

 acid, or with a small quantity of a very weak solution of chlorine. 

 The first of these reagents produced a curdy- white precipitate which 

 was entirely soluble in ammonia, and was consequently entirely pure 

 chloride of silver ; the second reagent was not at all coloured under 

 the circumstances described ; and lastly, the solution of bichloride of 

 palladium, which discovers the smallest quantity of iodine, produced 

 no effect. 



The portion of rock which had been subjected to the successive 

 action of alcohol and water, was mixed with water and treated with 

 weak nitric acid, which gradually dissolved it with brisk efferves- 

 cence, except a small white residue, which was collected on a 

 weighed filter. A part of this dried residue adhered to the filtering 

 paper, and had the soapy and soft feel of alumina; it adhered 

 slightly to the tongue, and was in fact a combination of silica and 

 alumina ; it weighed a small fraction of a grain ; the nitric solution 

 was slightly acid and colourless ; solution of starch gave no indica- 

 tion of iodine ; when saturated with ammonia it yielded slight traces 

 of alumina ; the solution exposed to the contact of the air became 

 gradually turbid and brown, and deposited brown flocculi, which, 

 after some days, were collected and found to be peroxide of manga- 

 nese ; it probably existed as protocarbonate in the rock. The solu- 

 tion was then treated with oxalate of ammonia, which precipitated 

 the lime, and potash afterwards threw down a little magnesia. 



From the facts above stated, M. Lassaigne concludes, — 

 1st. That the calcareous rock obtained west of the city of Dieppe, 

 on which the fuci or varech grow, contains no compound of iodine. 



