1815.] in the Physical Sciences. 13 



greater. It has a peculiar smell, is very volatile, and very poisonous 

 in its nature when taken internally. Its specific gravity is rather 

 less than four, that of water being one. 



Iodine, as far as experiment has hitherto gone, must be consi- 

 dered as a simple substance ; and it belongs to the class of sup- 

 porters, though it is by far the worst supporter known. Its vapour 

 supports the combustion of potassium, and it combines rapidly with 

 phosphorus, evolving much heat, though no light. When iodine 

 is heated, it is volatilized at rather a low temperature, and con- 

 verted into a beautiful violet-coloured vapour, from which it has 

 received its name. This vapour, as far as I can find, possesses very 

 little elasticity at the temperature of 212°. 



Iodine combines with chlorine, and forms a peculiar acid. It 

 does not appear to combine with oxygen. With hydrogen it unites, 

 and forms an acid very much resembling muriatic acid in its smell, 

 though I consider it as rather more pungent than that of muriatic 

 acid. It unites with sulphur, phosphorus, and the metals ] and 

 forms a class of bodies, analogous to the oxides, called iodes. Some 

 of these possess the properties of acids. It combines with alkalies 

 and earths, and forms with them two classes of salts. The first, 

 consisting of iodine and the base, may be considered as analogous 

 to the iodes; the second, consisting of iodine, oxygen, and the 

 base, have been called oxiodes, and may be considered as analogous 

 to the hyper-oxymuriates. It scarcely possesses the property of 

 separating carbonic acid from the bases, and cannot therefore be 

 united with the carbonates so as to form salts ; though these bodies 

 readily dissolve a portion of iodine. An atom of iodine weighs about 

 12-5. 



2.. Chlorine. — Chlorine has the property of combining with two 

 different proportions of oxygen, and of forming two new acids, 

 which have received the names of chloric and chlorous acids. The 

 first was discovered by Gay-Lussac ; the second, by Sir H. Davy. 

 The Germans have given to chlorine the name of halogen. 



It is scarcely wor«h while to notice the experiments of the Dutch 

 chemists L. A. Von Meerten and S. Stratingh on this gas, as I do 

 not perceive any thing new in them. Meerten says that chlorine 

 has the property of converting sulphurous acid into sulphuric acid, 

 and nitrous gas into nitric acid. These were the first two experi- 

 ments that I tried ; when Davy published his paper to show that 

 chlorine is still an uiidccoinposcd substance ; and I soon procured 

 the fullest evidence that neiilier of these gases is altered by pure 

 chlorine ; but when chlorine contains a mixture of common air, 

 which it u>;ually does, it renders nitrous gas yellow in an instant. 

 Meerten found likewise that ether burns in ciilorinc gas. This dis- 

 covery was made many years ago by Cruickshank, iuid ])ublished by 

 him in the last volume of Nicholson's quarto .lournal, and by n)y- 

 .self in the second and subsequent editions of my System of Che- 

 mistry ; nor is there any thing new with resj)ect to the burning of 

 the metals in chlorine gas, as Jar as tried hy these chemists. 



