Mr Wood and Mr Jones , On Complex Carbonates. 171 
Some observations on Complex Carbonates. By T. B. Wood, 
M.A., Gonville and Gains College, and H. O. Jones, M.A., Clare 
College. 
(Read 11 March 1907.] 
The experiments described in this paper were undertaken 
with the object of investigating the stability of the solutions 
made by Soldaini ( Gazz . Chim. Ital. 6. 322) and Ost ( Ber . d. d. 
Chem. Ges. 23. 1035), which contain copper sulphate, potassium 
carbonate and bicarbonate, are stable on boiling, and are used as 
substitutes for Fehling’s solution. Groger (Ber. d. d. Chem, Ges. 
34. 429) had found that these solutions deposited basic copper 
carbonate, or a double copper potassium carbonate, or both, on 
standing, and, under certain conditions, had obtained a salt which 
gave analytical numbers agreeing with the composition 
K 2 C0 3 .8Cu0.7C0 2 .17H 2 0. 
Copper salts dissolve freely in concentrated solutions of 
potassium carbonate to give deep blue solutions very like 
Soldaini’s solution, but these solutions give a black precipitate 
of hydrated copper oxide on boiling: this decomposition is pre- 
vented by the addition of bicarbonate. 
Extending these observations to other metallic salts we found 
that the salts of cobalt, nickel, iron (ferrous and ferric), manganese, 
chromium, aluminium, uranium, zinc, cadmium, bismuth, calcium, 
silver and magnesium all dissolved in concentrated solutions of 
potassium carbonate and in most cases deposited definite crystal- 
line double carbonates on standing. In the other cases, notably 
ferric salts, aluminium and chromium salts, no crystalline product 
could be obtained. Some of these salts we found had been 
prepared by Deville (Ann. de Chim. et de Phys. 80. 251) and 
the others by Reynolds (Jour. Chem. Soc. 1898, 263). 
The cobalt, nickel, magnesium, manganese and ferrous salts 
have the general formula K 2 C0 3 . M . C0 3 . 4H 2 0, are beautifully 
crystalline, dissolve in potassium carbonate solution but are de- 
composed by water. It is remarkable that this very interesting 
series of salts should have received so little notice that it is not 
mentioned in any of the ordinary text-books. 
Reynolds prepared the double copper carbonates by adding 
copper acetate to a concentrated potassium carbonate solution 
and found that three salts were deposited simultaneously : 
(1) blue hexagonal plates K 2 C0 3 .CuC0 3 , (2) pale blue silky 
needles K 2 C0 3 . CuC0 3 . H«0, (3) large greenish blue tables 
K 2 C0 3 . CuC0 3 . 4H 2 0. These salts were separated mechanically 
12—2 
