152 
necessary. Atacamite is known to occur in nature in three 
states of hydration, and as an example of the first I may 
mention a specimen from Algodon Bay, Bolivia, analysed by 
Bibra (Jaliresbericht, 1858, 740), which had the following 
composition, viz. : — 
Cu 
Cl 
.... 16-11 
0 
.... 12-51 
h 2 o ... 
.... 12-13 
100-00 
The formula corresponding with the above analysis being 
Cu 4 0 8 Cl 2 -f3H 2 0. The atacamite of Copiapo, Chili, as 
analysed by Field (Journ. Chem. Soc. (7) 3, 193) has the 
following composition, viz. — 
Cu ..... 
.... 56-38 
per cent. 
Cl 
.... 14-95 
?> 
O 
.... 10-78 
}} 
h 2 o ... 
.... 17-89 
>> 
100-00 
The formula for this being Cu 8 0 6 Cl 4 -l- 9H 2 0, or (Cu 4 0 3 C1 2 ) 2 
+ 9H 2 0. The third state of hydration is represented in the 
atacamite from Botallack, Cornwall, analysed by Church 
(Journ. Chem. Soc. (2) 3, 212), and that from Tocopilla, near 
Cobija, Bolivia, analysed by Berthier (Ann., des Mines (3) 
7, 542) the composition being as follows : — ■ 
Botallack Atacamite. 
Cu 52-90 
Tocopilla Atacamite. 
Cu 53-26 
Cl 
.... 14-76 
Cl 
.... 14-92 
O 
.... 10-49 
O 
.... 9-37 
f 2 o .. 
.... 22-45 
H 2 0 .. 
.... 22-45 
100-00 
100-00 
and the formula Cu 4 0 3 Cl 2 + 6H 2 0. 
Having given a general idea of the composition of the 
various atacamites, I will now point out how some of them 
can be prepared artificially. Field (Phil. Mag. (4) XXIV., 
1802, 124) prepared the last-mentioned variety by adding a 
solution of calcium hypochlorite to an excess of cupric sul- 
phate, and boiling the mixture for some time, when an 
