170 METALS AND THEIR COMBINATIONS. 



Filter the warm solution of ferrous chloride, mix it with 2 c.c. of hydrochloric 

 acid, and add to it slowly and gradually about 0.6 c.c. of nitric acid. Evap- 

 orate in a fume chamber as long as red vapors escape ; then test a few drops 

 with potassium ferricyanide, which should not give a blue precipitate ; if it 

 does, the solution has to be heated with a little more nitric acid until the con- 

 version into ferric chloride is complete and the potassium ferricyanide pro- 

 duces no precipitate. Ferric chloride thus obtained may be mixed with 4 c.c. 

 of hot water and set aside, when it forms a solid mass of Fe 2 Cl 6 .12H 2 O. How 

 much FeCl 2 , how much Fe 2 Cl 6 , and how much Fe 2 Cl 6 .12H 2 can be obtained 

 from 1 gramme of iron? 



Solution of chloride of iron, Liquor ferri chloridi, U. S. P. 

 This is a solution in water, containing 37.8 per cent, of the anhydrous 

 ferric chloride and some free hydrochloric acid. It is a reddish- 

 brown liquid of specific gravity 1.405, having the taste and reaction 

 of the dry salt. This solution, mixed with 3 volumes of alcohol 

 and left standing in a closed vessel for at least three months, forms 

 the tincture of chloride of iron, Tinctura ferri chloridi, U. S. P. By 

 the action of the alcohol on ferric chloride this is reduced to the 

 ferrous state, while at the same time a number of other compounds 

 are formed, imparting to the liquid an ethereal odor. 



Dialyzed iron is an aqueous solution of about 5 per cent, of ferric 

 hydroxide with some ferric chloride. It is made by slowly adding 

 to a solution of ferric chloride, ammonium hydroxide as long as the 

 precipitate of ferric hydroxide formed is redissolved in the ferric 

 chloride solution, on shaking violently. The clear solution thus 

 obtained is placed in a dialyzer floating in water, which latter is 

 renewed every day until it shows no reaction with silver nitrate. 

 The ammonium chloride passes through the membrane of the dialyzer 

 into the water, while all iron as hydroxide with some chloride is left 

 in solution. 



The combination of an oxide or hydroxide with a normal salt is 

 called usually a basic salt or oxy-salt ; dialyzed iron is a highly basic 

 oxychloride of iron. 



Ferrous iodide, PeI 2 . When water is poured upon a mixture of 

 metallic iron (fine wire is best) and iodine, the two elements combine 

 directly, forming a pale-green solution of ferrous iodide, from which 

 the salt may be obtained by evaporation. As it is oxidized and 

 decomposed easily by the action of the air, an official preparation, 

 the saccharated ferrous iodide, U. S. P., is made by adding about 80 

 parts of sugar of milk to 20 parts of ferrous iodide ; the sugar pre- 

 vents, to some extent, rapid oxidation. 



