31 
crystalline cuprite was observed adhering to the sides of 
the glass tube, whilst on allowing the tube to cool it was 
observed that a very considerable amount of cuprous 
chloride had crystallised out in beautiful transparent colour- 
less tetrahedrons. On the 14th day the tube was opened, 
as no further changes had taken place, and the contents 
examined and found to consist principally of cuprous 
chloride, with a small quantity of unaltered cupric chloride; 
there being at the same time a good amount of ferric sul- 
phate and cupric sulphate present. The deposit on the 
glass tube was cuprite. I was unable at the time to make 
any quantitative determination of the various substances 
formed in this reaction, and am therefore not prepared 
to say what the reaction was precisely. Of course the 
iron pyrites was considerably attacked, but there was 
no separation of free sulphur; free hydrochloric acid 
was also present, but not in sufficient quantity to dis- 
solve the small quantity of cuprite formed on the tube. 
The insoluble crystallised cuprous chloride was care- 
fully washed in distilled water in order to free it 
from the substances already mentioned, then placed in 
another glass tube, covered with distilled water, and the 
tube sealed up and heated for seven days in an air-bath 
at temperatures varying from 160° — 180°. On the second 
day a very marked amount of a bright-red substance had 
already formed on the sides of the tube, and here and there 
minute green spots of a substance somewhat resembling 
atacamite (CuCl 2 3CuH0-h^H 2 0) in colour. This tube was 
heated at the temperatures given for about two weeks, 
when it was observed that although the red deposit did not 
increase in quantity, the cuprous chloride was slowly 
undergoing decomposition, a black powder having separated 
out. On opening the tube a smell of hydrochloric acid was 
perceived. The liquid portion in the tube was poured out, 
and the solid portion (which principally consisted of unaltered 
