IRON, COBALT, AND NICKEL 36$ 



mixed with barium carbonate and an excess of hypochlorous acid be 

 added, or chlorine gas be passed through it, then at the ordinary 



colourless, anhydrous cupric saltfor instance, cupric sulphate when combined with 

 water forms blue and green salts, and violet when combined with ammonia. If steam be 

 passed through anhydrous copper sulphate the salt absorbs water and becomes heated ; if 

 ammonia be substituted for the water the heating becomes much more intense, and the 

 ealt breaks up into a fine violet powder. With water CuS0 4 ,5H 2 O is formed, and with 

 ammonia CuS0 4 ,5NH 3 , the number of water and; ammonia molecules retained by the 

 Bait being the same in each case, and as a proof of this, and that it is not an isolated . 

 coincidence, the remarkable fact must be borne in mind that water and ammonia con- 

 secutively, molecule for molecule, are capable of supplanting each other, and forming the 

 compounds CuSO 4 ,5K 2 0, CuS0 4 ,4H 2 0,NH 3 ; CuS0 4) 8H 2 0,2NH3 ; CuS0 4 ,2H 3 0,3NH 5 ; 

 CuS0 4 ,H 2 0,4NH 3 , and CuSO 4 ,5NH 3 . The last of these compounds was obtained by 

 Henry Rose, and my experiments have shown that more ammonia than this cannot be 

 retained. By adding to a strong solution of cupric sulphate sufficient ammonia to 

 dissolve the whole of the oxide precipitated, and then adding alcohol, Berzelius obtained 

 the compound CuS0 4 ,H 3 O,4NH 3 , &c. The law of substitution also assists in rendering 

 these phenomena clearer, because a compound of ammonia with water forms ammonium 

 hydroxide, NH 4 HO, and therefore these molecules combining with one another may also 

 interchange, as being of equal value. In general, those salts form stable ammoniacal 

 compounds which are capable of forming stable compounds with water of crystallisation ; , 

 and as ammonia is capable of combining with acids, and as some of the salts formed by 

 slightly energetic bases in their properties more closely resemble acids (that is, salts of 

 hydrogen) than those salts containing more energetic bases, we might expect to find 

 more stable and more easily-formed ammonio-metallio salts with metals and their 

 oxides having weaker basic properties than with those which form energetic bases. Thi# 

 explains why the salts of potassium, barium, &c., do not form ammonio-metallic salts, 

 whilst the salts of silver, copper, zinc, &c., easily form them, and the salts RX 5 still 

 more easily and with greater stability. This consideration also accounts for the great 

 stability of the ammoniacal compounds of cupric oxide compared with those of silver 

 oxide, since the former is displaced by the latter. It also enables us to see clearly the 

 distinction which exists in the stability of the cobaltamine salts containing salts corre- 

 ponding with cobaltous oxide, and those corresponding with higher oxides of cobalt, 

 for the latter are weaker bases than cobaltous oxides. The nature of the forces 

 and quality of the phenomena occurring during the formation of the most stable sub' 

 stances, and of such compounds as crystallisable compounds, are one and the same i t 

 although perhaps exhibited in a different degree. This, in my opinion, may be best 

 confirmed by examining the compounds of -carbon, because for this element the nature 

 of the forces acting during the formation of its compounds is well known. Let us take 

 as an example two unstable compounds of carbon. Acetic acid, C 2 H 4 O 2 (specific gravity 

 1-06), with water forms the hydrate, C 2 H 4 2 ,H 2 0, denser (1'07) than either of the com- 

 ponents, but unstable and easily decomposed, generally simply referred to as a 

 solution. Such also is the crystalline compound of oxalic acid, C 2 H 2 O 4 , with water, 

 C 2 H 2 O 4) 2H 2 0. Their formation might be predicted as starting from the hydrocarbon 

 C 2 H 6 , in which, as in any other, the hydrogen- may be exchanged for chlorine, the 

 water residue (hydroxyl), &o. The first substitution product with hydroxyl, C 2 H 5 (HO), 

 is stable ; it can be distilled without alteration, resists a temperature higher than 100, 

 and then does not give off water. This is ordinary alcohol. The second, C 2 H 4 (HO) 2 , 

 can also be distilled without change, but can be decomposed into water and C 2 H 4 O 

 (ethylene oxide or aldehyde) ; It boils at about 197, whilst the first hydrate boils at 78, 

 ft difference of about 100 The compound C 2 H 3 (HO) S will be the third product of such 

 substitution ; it ought to boil at about 300, but does not resist this temperature it de- 

 composes into H 2 and C i H 4 2 , where only one hydroxyl group remains, and the other 

 atom of oxygen is left in the same condition as in ethyler.e oxide, C 2 H 4 O. There is a proof 

 of this. Glycol, C 2 H 4 (HO) 2 , boils at 197, and forms water and ethylene oxide, which 



