Chemical Science. ^)5 



with antimony anil realgar lose in the intensity of the colour when 

 lonjr exposed to light, so that they should be preserved in black- 

 ened bottles. 



Cold favours the absorption of light ; heat favours the dispersion ; 

 boiUng water destroys the phosphorescence. Exposed to solar 

 liglit for a minute, and then taken into a dark place, some Bo- 

 lognian phosphorus shone for 4 minutes ; the third of those above, 

 for 34 minutes; the first (with antimony) for 149 minutes; and at 

 this period that prepared with realgar shone as brightly as it did 

 one hour before. A red heat applied for several hours destroyed 

 the power of the realgar preparation, very much weakened that 

 with antimony, but did not affect that of the arsenic compound. 



The light of an electric spark passed one inch above these phos- 

 phori makes them luminous. These phosphori shone even in the 

 daylight, but their light then appears white. — Kastner's Arch. 

 Bull. Univ. A. x. 50. 



11. Preparation of Iodine by M. Souberan.>— The following is 

 the process recommended by M. Souberan, by which he has 

 obtained as much as -^^th part of iodine from mother liquors, that 

 would yield none by the ordinary process. The mother liquors 

 from the soda works, are to be diluted with 4 or 5 times their weight 

 of water, and solution of sulphate of copper added, until precipita- 

 tion ceases. The deposit will consist of iodide of copper and sul- 

 phate of lime, and is to be separated. Large iron fihngs, or turn- 

 ings, are then to be put into the liquid and agitated, until all smell 

 of iodine has disappeared, by which process, the remaining portion 

 of iodine will separate as an iodide of copper, mixed with metallic 

 copper and the iron turnings, but easily separated by washing over. 

 These two precipitates are then to be acted upon separately, in one 

 of the following ways : 1. The iodide is to be mixed with two or 

 three times its weight of peroxide of manganese, and a sufficient 

 quantity of concentrated sulphuric acid, and then distilled, when all the 

 iodine will rise with some aqueous vapour ; or 2. The mixture of 

 iodide and oxide of manganese is to be heated in a retort to a high 

 temperature, when pure iodine will come over ; the residue is pul- 

 verulent, and can easily be extracted without breaking the vessel. — 

 Ann. des MineSy N. S. iii. 102. 



12. Action of Ammonia on heated Metals. — We gave an account 

 in our last volume of M. Savart's experiments on this subject. M. 

 Despretz claims the honour belonging to a prior discoverer on the 

 following points. The diminution in density of copper, iron, and 

 platina, after these metals have been employed in decomposing 

 hydrogen gas. This fact he had published in his lectures, and in 

 printed leaves, as early as December, 1827 ; and also the following, 

 that during the decomposition of bi-carburetted hydrogen by heat, 

 fusible white crystals were obt«ine<l, volatile at a low temperature 



