Intelligence and Miscellaneous Articles. 513 



Professor Airy gave an account of experiments on the polariza- 

 of light by the sky. It appeared that the light was polarized in a 

 plane passing through the sun, and that the plane of polarization 

 was not reversed in approaching the sun as had been formerly sug- 

 gested by M. Arago. Professor Airy found that he could ob- 

 serve the polarization within nine degrees of the sun in a horizontal 

 direction ; but that above and below the sun the traces disappeared 

 at a distance considerably greater. It was found in the course of 

 these experiments that very rough surfaces, as a stone wall, a gravel 

 walk, a carpet, produced some polarization by reflection ; and that 

 the plane of polarization in all cases passed through the point of 

 reflection and the source from which the light came. This commu- 

 nication gave rise to observations from other members. 



LIU. Intelligence and Miscellaneous Articles. 



ACTION OF IODINE ON STARCH. 



MLEROY, of Brussels, has found that water is requisite to 

 • the production of the blue colour which is produced by the 

 action of iodine on starch : in alcohol the iodine becomes merely 

 of a dark brown colour, and water causes the blue colour to appear. 

 M. Chevallier has also remarked that farinaceous substances 

 mixed with starch, which are always moist, when subjected to the 

 vapour of iodine, acquired a brown colour, while potato starch be- 

 came of a golden yellow merely. He concluded, from this circum- 

 stance, that iodide of starch is of a yellow colour, and that this, by 

 absorbing water, became blue hydrate, and he found that when this 

 yellow compound was touched with a moistened tube, it became in- 

 stantly blue. — Ann. de Chim. Medicale, May 1833. 



ANALYSIS OF OIL OF CLOVES, INDIGO, &C. 



M. Dumas found that oil of cloves, even when perfectly transpa- 

 rent, may still contain much water, which may be separated by 

 merely digesting it at a temperature of 140° to 175° with chloride 

 of calcium : the solution of chloride subsides to the bottom of the 

 vessel, and the pure oil floats upon it. 



The atomic weight of the oil was attempted to be determined 

 by combining it with soda ; but definite compounds could not be 

 obtained ; for when the oil is heated with the alkali, a pearly mass 

 forms on cooling, which contains an enormous quantity of free alkali, 

 that cannot be separated. 



Excess of ammoniacal gas was passed into the oil, and a com- 

 pound was obtained which, estimating 21 25 as the atomic weight 

 of the ammonia, would give 22 as that of the oil of cloves ( or taking 

 Bmmonia at 17, that of the oil would be nearly 18). The compound 

 formed is in small very brilliant crystals ; but they decompose imme- 

 diately on coming into the air, and therefore their analysis was not 

 attempted. 



The following are the experimental and calculated compositions 

 of oil of cloves. 



Third Strict. Vol.4. No. 22. Aprd 1834. t S 



